AD9957BSVZ-REEL13 [ADI]
IC SPECIALTY TELECOM CIRCUIT, QFP48, PLASTIC, MS-026-AED-HD, TQFP-48, Telecom IC:Other;
| 型号： | AD9957BSVZ-REEL13 |
| 厂家： | 
ADI |
| 描述： | IC SPECIALTY TELECOM CIRCUIT, QFP48, PLASTIC, MS-026-AED-HD, TQFP-48, Telecom IC:Other 电信 电信集成电路 |
| 文件： | 总64页 (文件大小：1229K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
1 GSPS Quadrature Digital Upconverter
with 18-Bit I/Q Data Path and 14-Bit DAC
Data Sheet
AD9957
FEATURES
GENERAL DESCRIPTION
1 GSPS internal clock speed (up to 400 MHz analog output)
Integrated 1 GSPS 14-bit DAC
250 MSPS input data rate
The AD9957 functions as a universal I/Q modulator and agile
upconverter for communications systems where cost, size, power
consumption, and dynamic performance are critical. The AD9957
integrates a high speed, direct digital synthesizer (DDS), a high
performance, high speed, 14-bit digital-to-analog converter (DAC),
clock multiplier circuitry, digital filters, and other DSP functions
onto a single chip. It provides baseband upconversion for data
transmission in a wired or wireless communications system.
Phase noise ≤ −125 dBc/Hz (400 MHz carrier @ 1 kHz offset)
Excellent dynamic performance >80 dB narrow-band SFDR
8 programmable profiles for shift keying
Sin(x)/(x) correction (inverse sinc filter)
Reference clock multiplier
Internal oscillator for a single crystal operation
Software and hardware controlled power-down
Integrated RAM
Phase modulation capability
Multichip synchronization
Easy interface to Blackfin SPORT
Interpolation factors from 4× to 252×
Interpolation DAC mode
The AD9957 is the third offering in a family of quadrature
digital upconverters (QDUCs) that includes the AD9857 and
AD9856. It offers performance gains in operating speed, power
consumption, and spectral performance. Unlike its predecessors,
it supports a 16-bit serial input mode for I/Q baseband data.
The device can alternatively be programmed to operate either as
a single tone, sinusoidal source or as an interpolating DAC.
Gain control DAC
The reference clock input circuitry includes a crystal oscillator,
a high speed, divide-by-two input, and a low noise PLL for
multiplication of the reference clock frequency.
Internal divider allows references up to 2 GHz
1.8 V and 3.3 V power supplies
100-lead TQFP_EP package
The user interface to the control functions includes a serial port
easily configured to interface to the SPORT of the Blackfin®
DSP and profile pins to enable fast and easy shift keying of any
signal parameter (phase, frequency, or amplitude).
APPLICATIONS
HFC data, telephony, and video modems
Wireless base station transmissions
Broadband communications transmissions
Internet telephony
FUNCTIONAL BLOCK DIAGRAM
I
DATA
FOR
XMIT
FORMAT AND
INTERPOLATE
14-BIT DAC
I/Q DATA
Q
NCO
AD9957
TIMING
AND
CONTROL
REFERENCE CLOCK
INPUT CIRCUITRY
USER INTERFACE
REFERENCE CLOCK INPUT
Figure 1.
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2007–2012 Analog Devices, Inc. All rights reserved.
AD9957
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
RAM Control .................................................................................. 27
RAM Overview........................................................................... 27
RAM Segment Registers............................................................ 27
RAM State Machine................................................................... 27
RAM Trigger (RT) Pin............................................................... 27
Load/Retrieve RAM Operation................................................ 28
RAM Playback Operation......................................................... 28
Overview of RAM Playback Modes......................................... 29
RAM Ramp-Up Mode........................................................... 29
RAM Bidirectional Ramp Mode .......................................... 30
RAM Continuous Bidirectional Ramp Mode .................... 32
RAM Continuous Recirculate Mode................................... 33
Clock Input (REF_CLK)................................................................ 34
REFCLK Overview..................................................................... 34
Crystal Driven REF_CLK ......................................................... 34
Direct Driven REF_CLK ........................................................... 34
Phase-Locked Loop (PLL) Multiplier...................................... 35
PLL Charge Pump...................................................................... 36
External PLL Loop Filter Components ................................... 36
PLL Lock Indication .................................................................. 36
Additional Features ........................................................................ 37
Output Shift Keying (OSK)....................................................... 37
Manual OSK............................................................................ 37
Automatic OSK....................................................................... 37
Profiles ......................................................................................... 38
I/O_UPDATE Pin ...................................................................... 38
Automatic I/O Update............................................................... 38
Power-Down Control ................................................................ 39
General-Purpose I/O (GPIO) Port .......................................... 39
Synchronization of Multiple Devices........................................... 40
Overview ..................................................................................... 40
Clock Generator ......................................................................... 40
Applications....................................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 4
Specifications..................................................................................... 5
Electrical Specifications............................................................... 5
Absolute Maximum Ratings............................................................ 8
ESD Caution.................................................................................. 8
Pin Configuration and Function Descriptions............................. 9
Typical Performance Characteristics ........................................... 12
Modes of Operation ....................................................................... 16
Overview...................................................................................... 16
Quadrature Modulation Mode ................................................. 17
BlackFin Interface (BFI) Mode................................................. 18
Interpolating DAC Mode .......................................................... 19
Single Tone Mode....................................................................... 20
Signal Processing ............................................................................ 21
Parallel Data Clock (PDCLK)................................................... 21
Transmit Enable Pin (TxEnable).............................................. 21
Input Data Assembler ................................................................ 22
Inverse CCI Filter ....................................................................... 23
Fixed Interpolator (4×).............................................................. 23
Programmable Interpolating Filter .......................................... 24
QDUC Mode........................................................................... 24
BFI Mode................................................................................. 24
Quadrature Modulator .............................................................. 25
DDS Core..................................................................................... 25
Inverse Sinc Filter ....................................................................... 25
Output Scale Factor (OSF) ........................................................ 26
14-Bit DAC .................................................................................. 26
Auxiliary DAC ........................................................................ 26
Rev. C | Page 2 of 64
Data Sheet
AD9957
Sync Generator ............................................................................40
Sync Receiver...............................................................................41
Setup/Hold Validation................................................................42
Synchronization Example ..........................................................44
I/Q Path Latency .........................................................................45
Example....................................................................................45
Power Supply Partitioning .............................................................46
3.3 V Supplies ..............................................................................46
I/O_RESET—Input/Output Reset........................................48
I/O_UPDATE—Input/Output Update ................................48
Serial I/O Timing Diagrams......................................................48
MSB/LSB Transfers.....................................................................48
I/O_UPDATE, SYNC_CLK, and System Clock
Relationships................................................................................49
Register Map and Bit Descriptions ...............................................50
Register Map................................................................................50
Register Bit Descriptions............................................................55
Control Function Register 1 (CFR1)....................................55
Control Function Register 2 (CFR2)....................................56
Control Function Register 3 (CFR3)....................................58
Auxiliary DAC Control Register...........................................58
I/O Update Rate Register.......................................................58
RAM Segment Register 0.......................................................58
RAM Segment Register 1.......................................................59
Amplitude Scale Factor (ASF) Register ...............................59
Multichip Sync Register .........................................................59
Profile Registers...........................................................................60
Profile<7:0> Register—Single Tone......................................60
Profile<7:0> Register—QDUC .............................................60
RAM Register..........................................................................60
GPIO Configuration Register ...............................................60
GPIO Data Register................................................................60
Outline Dimensions........................................................................61
Ordering Guide ...........................................................................61
DVDD_I/O (Pin 11, Pin 15, Pin 21, Pin 28, Pin 45, Pin 56,
Pin 66) ......................................................................................46
AVDD (Pin 74 to Pin 77 and Pin 83) ...................................46
1.8 V Supplies ..............................................................................46
DVDD (Pin 17, Pin 23, Pin 30, Pin 47, Pin 57, Pin 64).....46
AVDD (Pin 3) ..........................................................................46
AVDD (Pin 6) ..........................................................................46
AVDD (Pin 89 and Pin 92)....................................................46
Serial Programming........................................................................47
Control Interface—Serial I/O....................................................47
General Serial I/O Operation....................................................47
Instruction Byte...........................................................................47
Instruction Byte Information Bit Map .................................47
Serial I/O Port Pin Descriptions ...............................................47
SCLK—Serial Clock................................................................47
CS
—Chip Select Bar ...............................................................47
SDIO—Serial Data Input/Output.........................................47
SDO—Serial Data Out ...........................................................48
Rev. C | Page 3 of 64
AD9957
Data Sheet
REVISION HISTORY
4/12—Rev. B to Rev. C
1/08—Rev. 0 to Rev. A
Changes to Table 1............................................................................ 7
Changes to Table 3.......................................................................... 11
Change to Sync Generator Section............................................... 41
Changes to Sync Receiver Section and Setup/Hold Validation
Section.............................................................................................. 42
Changes to Table 13........................................................................ 50
Changes to Table 19........................................................................ 57
Changes to Table 26........................................................................ 59
Changes to REFCLK Multiplier Specification...............................3
Changes to I/O_Update/Profile<2:0>/RT Timing
Characteristics and I/Q Input Timing Characteristics.................5
Replaced Pin Configuration and Function Descriptions
Section.................................................................................................8
Changes to Figure 25 Through Figure 29.................................... 15
Deleted Table 4, Renumbered Sequentially ................................ 20
Changes to DDS Core Section...................................................... 24
Changes to Figure 47 and Table 6................................................. 33
Replaced Synchronization of Multiple Devices Section............ 39
Added I/Q Path Latency Section.................................................. 44
Added Power Supply Partitioning Section.................................. 45
Changes to General Serial I/O Operation Section..................... 46
Changes to Table 13 ....................................................................... 48
Changes to Table 14 ....................................................................... 49
Changes to Table 19 ....................................................................... 54
Changes to Table 20 ....................................................................... 56
Changes to GPIO Configuration Register and
10/10—Rev. A to Rev. B
Changes to Data Rate in Features Section..................................... 1
Changes to Specifications Section.................................................. 6
Added EPAD Notation to Figure 4 and Table 3 ........................... 9
Changes to XTAL_SEL Pin Description...................................... 11
Changes to BlackFin Interface (BFI) Mode Section .................. 18
Changes to Figure 30 and Figure 31............................................. 22
Changes to Programmable Interpolating Filter Section............ 24
Changes to Fifth Paragraph of Quadrature Modulator Section......25
Changes to RAM Segment Registers Section ............................. 27
Changes to RAM Playback Operation Section........................... 28
Changes to Control Interface—Serial I/O Section..................... 47
Added to I/O_UPDATE, SYNC_CLK, and System Clock
Relationships Section and Figure 64............................................ 49
Changes to Default Values of Profile 0 Register—Single Tone
(0x0E) and Profile 0 Register—QDUC (0x0E) in Table 14....... 51
Changes to Default Values in Table 15......................................... 52
Changes to Default Values in Table 16......................................... 53
Changes to Default Values in Table 17......................................... 54
Updated Outline Dimensions ....................................................... 61
GPIO Data Register Sections........................................................ 58
5/07—Revision 0: Initial Version
Rev. C | Page 4 of 64
Data Sheet
AD9957
SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
AVDD (1.8V) and DVDD (1.8V) = 1.8 V 5%, AVDD (3.3V) = 3.3 V 5%, DVDD_I/O (3.3V) = 3.3 V 5%, T = 25°C, RSET = 10 kΩ,
OUT = 20 mA, external reference clock frequency = 1000 MHz with REFCLK multiplier disabled, unless otherwise noted.
I
Table 1.
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
REF_CLK INPUT CHARACTERISTICS
Frequency Range
REFCLK Multiplier
Disabled
60
10001 MHz
Enabled
Full temperature range
Full temperature range
3.2
60
MHz
MHz
MHz
MHz
pF
Maximum REFCLK Input Divider Frequency
Minimum REFCLK Input Divider Frequency
External Crystal
1500 1900
25
25
3
2.8
35
Input Capacitance
Input Impedance (Differential)
Input Impedance (Single-Ended)
Duty Cycle
kΩ
1.4
kΩ
%
%
mV p-p
mV p-p
REFCLK multiplier disabled
REFCLK multiplier enabled
Single-ended
45
40
50
100
55
60
1000
2000
REF_CLK Input Level
Differential
REFCLK MULTIPLIER VCO GAIN CHARACTERISTICS
VCO Gain (KV) @ Center Frequency
VCO0 range setting
VCO1 range setting
VCO2 range setting
VCO3 range setting
VCO4 range setting
VCO5 range setting2
429
500
555
750
789
850
MHz/V
MHz/V
MHz/V
MHz/V
MHz/V
MHz/V
REFCLK_OUT CHARACTERISTICS
Maximum Capacitive Load
Maximum Frequency
DAC OUTPUT CHARACTERISTICS
Full-Scale Output Current
Gain Error
20
25
pF
MHz
8.6
−10
20
31.6
+10
2.3
mA
%FS
µA
Output Offset
Differential Nonlinearity
Integral Nonlinearity
Output Capacitance
0.8
1.5
5
LSB
LSB
pF
Residual Phase Noise
REFCLK Multiplier
@ 1 kHz Offset, 20 MHz AOUT
Disabled
Enabled @ 20×
−152
−140
−140
dBc/Hz
dBc/Hz
dBc/Hz
V
Enabled @ 100×
AC Voltage Compliance Range
SPURIOUS-FREE DYNAMIC RANGE (SFDR SINGLE TONE)
fOUT = 20.1 MHz
fOUT = 98.6 MHz
fOUT = 201.1 MHz
−0.5
+0.5
−70
−69
−61
−54
dBc
dBc
dBc
dBc
fOUT = 397.8 MHz
Rev. C | Page 5 of 64
AD9957
Data Sheet
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
NOISE SPECTRAL DENSITY (NSD)
Single Tone
fOUT = 20.1 MHz
fOUT = 98.6 MHz
fOUT = 201.1 MHz
fOUT = 397.8 MHz
−167
−162
−157
−151
dBm/Hz
dBm/Hz
dBm/Hz
dBm/Hz
TWO-TONE INTERMODULATION DISTORTION (IMD)
fOUT = 25 MHz
fOUT = 50 MHz
I/Q rate = 62.5 MSPS; 16× interpolation
2.5 Msymbols/s, QPSK, 4× oversampled
−82
−78
−73
dBc
dBc
dBc
fOUT = 100 MHz
MODULATOR CHARACTERISTICS
Input Data
Error Vector Magnitude
0.53
0.77
%
%
270.8333 ksymbols/s, GMSK, 32×
oversampled
2.5 Msymbols/s, 256-QAM, 4×
oversampled
0.35
%
WCDMA—FDD (TM1), 3.84 MHz Bandwidth,
5 MHz Channel Spacing
Adjacent Channel Leakage Ratio (ACLR)
IF = 143.88 MHz
−78
−78
dBc
dBc
Carrier Feedthrough
SERIAL PORT TIMING CHARACTERISTICS
Maximum SCLK Frequency
Minimum SCLK Pulse Width
70
2
Mbps
ns
ns
Low
High
4
4
Maximum SCLK Rise/Fall Time
ns
Minimum Data Setup Time to SCLK
Minimum Data Hold Time to SCLK
Maximum Data Valid Time in Read Mode
I/O_UPDATE/PROFILE<2:0>/RT TIMING CHARACTERISTICS
Minimum Pulse Width
5
0
ns
ns
ns
11
High
1
SYNC_CLK
cycle
Minimum Setup Time to SYNC_CLK
Minimum Hold Time to SYNC_CLK
I/Q INPUT TIMING CHARACTERISTICS
Maximum PDCLK Frequency
Minimum I/Q Data Setup Time to PDCLK
Minimum I/Q Data Hold Time to PDCLK
Minimum TxEnable Setup Time to PDCLK
Minimum TxEnable Hold Time to PDCLK
MISCELLANEOUS TIMING CHARACTERISTICS
Wake-Up Time3
Fast Recovery Mode
Full Sleep Mode
Minimum Reset Pulse Width High
DATA LATENCY (PIPELINE DELAY)
Data Latency Single Tone Mode
Frequency, Phase-to-DAC Output
1.75
0
ns
ns
250
MHz
ns
ns
ns
ns
1.75
0
1.75
0
1
8
SYSCLK cycles4
μs
SYSCLK cycles4
150
5
79
SYSCLK cycles4
Rev. C | Page 6 of 64
Data Sheet
AD9957
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
CMOS LOGIC INPUTS
Voltage
Logic 1
Logic 0
2.0
V
V
0.8
Current
Logic 1
Logic 0
Input Capacitance
XTAL_SEL INPUT
90
90
2
150
150
µA
µA
pF
Logic 1 Voltage
Logic 0 Voltage
Input Capacitance
CMOS LOGIC OUTPUTS
Voltage
1.25
2.8
V
V
pF
0.6
0.4
2
1 mA load
Logic 1
Logic 0
V
V
POWER SUPPLY CURRENT
DVDD_I/O (3.3V) Pin Current Consumption
DVDD (1.8V) Pin Current Consumption
AVDD (3.3V) Pin Current Consumption
AVDD (1.8V) Pin Current Consumption
POWER CONSUMPTION
Single Tone Mode
Continuous Modulation
Inverse Sinc Filter Power Consumption
Full Sleep Mode
QDUC mode
QDUC mode
QDUC mode
QDUC mode
16
610
28
mA
mA
mA
mA
105
800
1400 1800
150
12
mW
mW
mW
mW
8× interpolation
200
40
1 The system clock is limited to 750 MHz maximum in BFI mode.
2 The gain value for VCO range Setting 5 is measured at 1000 MHz.
3 Wake-up time refers to the recovery from analog power-down modes. The longest time required is for the Reference Clock Multiplier PLL to relock to the reference.
4 SYSCLK cycle refers to the actual clock frequency used on-chip by the DDS. If the reference clock multiplier is used to multiply the external reference clock frequency,
the SYSCLK frequency is the external frequency multiplied by the reference clock multiplication factor. If the reference clock multiplier and divider are not used, the
SYSCLK frequency is the same as the external reference clock frequency.
Rev. C | Page 7 of 64
AD9957
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
DIGITAL INPUTS
DVDD_I/O
Parameter
Rating
AVDD (1.8V), DVDD (1.8V) Supplies
AVDD (3.3V), DVDD_I/O (3.3V) Supplies
Digital Input Voltage
XTAL_SEL
Digital Output Current
Storage Temperature Range
Operating Temperature Range
θJA
2 V
4 V
INPUT
−0.7 V to +4 V
−0.7 V to +2.2 V
5 mA
−65°C to +150°C
−40°C to +85°C
22°C/W
AVOID OVERDRIVING DIGITAL INPUTS.
FORWARD BIASING ESD DIODES MAY
COUPLE DIGITAL NOISE ONTO POWER
PINS.
θJC
2.8°C/W
Figure 2. Equivalent Input Circuit
Maximum Junction Temperature
Lead Temperature, Soldering (10 sec)
150°C
300°C
DAC OUTPUTS
AVDD
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
IOUT
IOUT
MUST TERMINATE OUTPUTS TO AGND
FOR CURRENT FLOW. DO NOT EXCEED
THE OUTPUT VOLTAGE COMPLIANCE
RATING.
Figure 3. Equivalent Output Circuit
ESD CAUTION
Rev. C | Page 8 of 64
Data Sheet
AD9957
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
75
74
73
72
71
70
69
68
67
66
AVDD (3.3V)
AVDD (3.3V)
NC
PLL_LOOP_FILTER
AVDD (1.8V)
AGND
1
2
3
4
5
6
7
8
9
PIN 1
INDICATOR
AGND
NC
AGND
I/O_RESET
CS
AVDD (1.8V)
SYNC_IN+
SCLK
SYNC_IN–
SDO
SYNC_OUT+
SYNC_OUT–
SDIO
10
11
12
13
14
15
16
17
18
19
20
21
DVDD_I/O (3.3V)
65 DGND
64
DVDD_I/O (3.3V)
SYNC_SMP_ERR
DGND
AD9957
DVDD (1.8V)
TQFP-100 (E_PAD)
TOP VIEW
(Not to Scale)
63
DGND
MASTER_RESET
DVDD_I/O (3.3V)
62 DGND
61
NC
60 OSK
59
DGND
DVDD (1.8V)
I/O_UPDATE
EXT_PWR_DWN
PLL_LOCK
58
57
56
DGND
DVDD (1.8V)
CCI_OVFL
DVDD_I/O (3.3V)
55 SYNC_CLK
DVDD_I/O (3.3V)
54
53
52
51
DGND 22
PROFILE0
DVDD (1.8V)
23
24
25
PROFILE1
PROFILE2
NC
D17
RT
NOTES
1. NC = NO CONNECT.
2. EXPOSED PAD SHOULD BE SOLDERED TO GROUND.
Figure 4. Pin Configuration
Rev. C | Page 9 of 64
AD9957
Data Sheet
Table 3. Pin Function Descriptions
Pin No.
Mnemonic
I/O1 Description
Not Connected. Allow device pin to float.
1, 24, 61, 72, 86,
87, 93, 97 to 100
NC
2
PLL_LOOP_FILTER
AVDD (1.8V)
AVDD (3.3V)
I
I
I
I
PLL-Loop Filter Compensation. See External PLL Loop Filter Components section.
3, 6, 89, 92
74 to 77, 83
17, 23, 30, 47, 57,
64
Analog Core VDD. 1.8 V analog supplies.
Analog DAC VDD. 3.3 V analog supplies.
Digital Core VDD. 1.8 V digital supplies.
DVDD (1.8V)
11, 15, 21, 28, 45,
56, 66
4, 5, 73, 78, 79,
82, 85, 88, 96
13, 16, 22, 29, 46,
58, 62, 63, 65
7
DVDD_I/O (3.3V)
AGND
I
I
I
I
Digital Input/Output VDD. 3.3 V digital supplies.
Analog Ground.
DGND
Digital Ground.
SYNC_IN+
Synchronization Signal, Digital Input (Rising Edge Active). Synchronization signal from
external master to synchronize internal subclocks. See the Synchronization of Multiple
Devices section.
8
SYNC_IN−
I
Synchronization Signal, Digital Input (Falling Edge Active). Synchronization signal from
external master to synchronize internal subclocks. See the Synchronization of Multiple
Devices section.
9
SYNC_OUT+
SYNC_OUT−
SYNC_SMP_ERR
O
O
O
Synchronization Signal, Digital Output (Rising Edge Active). Synchronization signal from
internal device subclocks to synchronize external slave devices. See the Synchronization of
Multiple Devices section.
Synchronization Signal, Digital Output (Falling Edge Active). Synchronization signal from
internal device subclocks to synchronize external slave devices. See the Synchronization of
Multiple Devices section.
Synchronization Sample Error, Digital Output (Active High). A high on this pin indicates
that the AD9957 did not receive a valid sync signal on SYNC_IN+/SYNC_IN−. See the
Synchronization of Multiple Devices section.
10
12
14
18
MASTER_RESET
EXT_PWR_DWN
I
I
Master Reset, Digital Input (Active High). This pin clears all memory elements and sets
registers to default values.
External Power-Down, Digital Input (Active High). A high level on this pin initiates the
currently programmed power-down mode. See the Power-Down Control section for
further details. If unused, tie to ground.
19
20
PLL_LOCK
CCI_OVFL
D<17:0>
O
PLL Lock, Digital Output (Active High). A high on this pin indicates that the clock multiplier
PLL has acquired lock to the reference clock input.
CCI Overflow Digital Output, Active High. A high on this pin indicates a CCI filter overflow.
This pin remains high until the CCI overflow condition is cleared.
Parallel Data Input Bus (Active High). These pins provide the interleaved, 18-bit, digital, I
and Q vectors for the modulator to upconvert. Also used for a GPIO port in Blackfin
interface mode.
O
25 to 27, 31 to
39, 42 to 44, 48
to 50
I/O
42
43
40
41
SPORT I-DATA
SPORT Q-DATA
PDCLK
I
I
O
I
In Blackfin interface mode, this pin serves as the I-data serial input.
In Blackfin interface mode, this pin serves as the Q-data serial input.
Parallel Data Clock, Digital Output (Clock). See the Signal Processing section for details.
Transmit Enable, Digital Input (Active High). See the Signal Processing section for details.
TxENABLE/FS
In Blackfin interface mode, this pin serves as the FS input to receive the RFS output signal
from the Blackfin.
51
RT
I
RAM Trigger, Digital Input (Active High). This pin provides control for the RAM amplitude
scaling function. When this function is engaged, a high sweeps the amplitude from the
beginning RAM address to the end. A low sweeps the amplitude from the end RAM
address to the beginning. If unused, connect to ground or supply.
52 to 54
55
PROFILE<2:0>
SYNC_CLK
I
Profile Select Pins, Digital Inputs (Active High). These pins select one of eight
phase/frequency profiles for the DDS core (single tone or carrier tone). Changing the state
of one of these pins transfers the current contents of all I/O buffers to the corresponding
registers. State changes should be set up to the SYNC_CLK pin.
Output System Clock/4, Digital Output (Clock). The I/O_UPDATE and PROFILE<2:0> pins
should be set up to the rising edge of this signal.
O
Rev. C | Page 10 of 64
Data Sheet
AD9957
Pin No.
Mnemonic
I/O1 Description
59
I/O_UPDATE
I/O
Input/Output Update; Digital Input Or Output (Active High) Depending on the Internal I/O
Update Active Bit. A high on this pin indicates a transfer of the contents of the I/O buffers
to the corresponding internal registers.
60
67
OSK
I
Output Shift Keying, Digital Input (Active High). When using OSK (manual or automatic),
this pin controls the OSK function. See the Output Shift Keying (OSK) section of the data
sheet for details. When not using OSK, tie this pin high.
Serial Data Input/Output, Digital Input/Output (Active High). This pin can be either
unidirectional or bidirectional (default), depending on configuration settings. In
bidirectional serial port mode, this pin acts as the serial data input and output. In
unidirectional, it is an input only.
SDIO
I/O
68
69
70
71
SDO
O
I
Serial Data Output, Digital Output (Active High). This pin is only active in unidirectional
serial data mode. In this mode, it functions as the output. In bidirectional mode, this pin is
not operational and should be left floating.
Serial Data Clock. Digital clock (rising edge on write, falling edge on read). This pin
provides the serial data clock for the control data path. Write operations to the AD9957
use the rising edge. Readback operations from the AD9957 use the falling edge.
Chip Select, Digital Input (Active Low). Bringing this pin low enables the AD9957 to detect
serial clock rising/falling edges. Bringing this pin high causes the AD9957 to ignore input
on the serial data pins.
Input/Output Reset, Digital Input (Active High). Rather than resetting the entire device
during a failed communication cycle, when brought high, this pin resets the state machine
of the serial port controller and clears any I/O buffers that have been written since the last
I/O update. When unused, tie this pin to ground to avoid accidental resets.
SCLK
CS
I
I/O_RESET
I
80
81
84
IOUT
O
O
O
Open-Source DAC Complementary Output Source. Analog output, current mode. Connect
through 50 Ω to AGND.
Open-Source DAC Output Source. Analog output, current mode. Connect through 50 Ω to
AGND.
Analog Reference Pin. This pin programs the DAC output full-scale reference current.
Attach a 10 kΩ resistor to AGND.
IOUT
DAC_RSET
90
91
REF_CLK
REF_CLK
I
I
Reference Clock Input. Analog input. See the REFCLK Overview section for more details.
Complementary Reference Clock Input. Analog input. See the REFCLK Overview section
for more details.
94
REFCLK_OUT
XTAL_SEL
O
I
Reference Clock Output. Analog output. See the REFCLK Overview section for more
details.
Crystal Select (1.8 V Logic). Analog input (active high). Driving the XTAL_SEL pin high enables
the internal oscillator to be used with a crystal resonator. If unused, connect it to AGND.
95
(EPAD)
Exposed Pad
(EPAD)
The EPAD should be soldered to ground.
1 I = input, O = output.
Rev. C | Page 11 of 64
AD9957
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
1
1
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–10
–20
–30
–40
–50
–60
1
–70
–80
1
–90
–100
CENTER 102MHz
5kHz/DIV
SPAN 50kHz
START 0Hz
50MHz/DIV
STOP 500MHz
Figure 8. Narrow-Band View of Figure 5
(with Carrier and Lower Sideband Suppression)
Figure 5. 15.625 kHz Quadrature Tone, Carrier = 102 MHz,
CCI = 16, fS = 1 GHz
1
1
0
0
–10
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–20
–30
–40
–50
–60
–70
–80
–90
–100
1
1
CENTER 222MHz
5kHz/DIV
SPAN 50kHz
START 0MHz
50MHz/DIV
STOP 500MHz
Figure 9. Narrow-Band View of Figure 6
(with Carrier And Lower Sideband Suppression)
Figure 6. 15.625 kHz Quadrature Tone, Carrier = 222 MHz,
CCI = 16, fS = 1 GHz
1
1
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
1
1
CENTER 372MHz
5kHz/DIV
SPAN 50kHz
START 0Hz
50MHz/DIV
STOP 500MHz
Figure 7. 15.625 kHz Quadrature Tone, Carrier = 372 MHz,
CCI = 16, fS = 1 GHz
Figure 10. Narrow-Band View of Figure 7
(with Carrier and Lower Sideband Suppression)
Rev. C | Page 12 of 64
Data Sheet
AD9957
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–100
START 0Hz
50MHz/DIV
STOP 500MHz
CENTER 102MHz
2MHz/DIV
SPAN 20MHz
Figure 11. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 102 MHz, fS = 1 GHz
Figure 14. Narrow-Band View of Figure 11
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
CENTER 222MHz
2MHz/DIV
SPAN 20MHz
START 0MHz
50MHz/DIV
STOP 500MHz
Figure 15. Narrow-Band View of Figure 12
Figure 12. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 222 MHz, fS = 1 GHz
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
START 0Hz
50MHz/DIV
STOP 500MHz
CENTER 372MHz
2MHz/DIV
SPAN 20MHz
Figure 13. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 372 MHz, fS = 1 GHz
Figure 16. Narrow-Band View of Figure 13
Rev. C | Page 13 of 64
AD9957
Data Sheet
–50
–55
–60
–65
–70
–90
–100
–110
–120
–130
–140
–150
–160
–170
fOUT = 397.8MHz
fOUT = 201.1MHz
fOUT = 98.6MHz
SFDR WITHOUT PLL
SFDR WITH PLL
fOUT = 20.1MHz
–75
0
50
100
150
200
250
300
350
400
10
100
1k
10k
100k
1M
10M
100M
FREQUENCY OUT (MHz)
FREQUENCY OFFSET (Hz)
Figure 17. Wideband SFDR vs. Output Frequency in Single Tone Mode,
PLL with REFCLK = 15.625 MHz × 64
Figure 20. Residual Phase Noise, System Clock = 1 GHz
–90
–45
fOUT = 397.8MHz
LOW SUPPLY
–100
–110
–120
–130
–140
–150
–160
–50
HIGH SUPPLY
fOUT = 201.1MHz
–55
–60
–65
–70
–75
fOUT = 20.1MHz
fOUT = 98.6MHz
1M 10M
FREQUENCY OFFSET (Hz)
10
100
1k
10k
100k
100M
0
50
100
150
200
250
300
350
400
450
FREQUENCY OUT (MHz)
Figure 21. Residual Phase Noise Using the REFCLK Multiplier,
REFCLK = 50 MHz with 20x Multiplication, System Clock = 1 GHz
Figure 18. SFDR vs. Output Frequency and Supply ( 5%) in Single Tone
Mode, REFCLK = 1 GHz
1200
–50
DVDD 1.8V
–40°C
1000
+85°C
–55
–60
–65
–70
–75
800
600
400
AVDD 1.8V
AVDD 3.3V
DVDD 3.3V
200
0
100
200
300
400
500
600
700
800
900 1000
0
50
100
150
200
250
300
350
400
450
SYSTEM CLOCK FREQUENCY (MHz)
FREQUENCY OUT (MHz)
Figure 22. Power Dissipation vs. System Clock (PLL Disabled)
Figure 19. SFDR vs. Frequency and Temperature in Single Tone Mode,
REFCLK = 1 GHz
Rev. C | Page 14 of 64
Data Sheet
AD9957
1200
1000
800
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
DVDD 1.8V
600
400
AVDD 1.8V
AVDD 3.3V
DVDD 3.3V
600
200
0
400
CENTER 143.86MHz
2.55MHz/DIV
SPAN 25.5MHz
500
700
800
900
1000
SYSTEM CLOCK FREQUENCY (MHz)
Tx CHANNEL
W-CDMA SGFF FWD
BANDWIDTH: 3.84MHz
POWER: –11.88dBm
Figure 23. Power Dissipation vs. System Clock (PLL Enabled)
ADJACENT CHANNEL
BANDWIDTH: 3.84MHz
SPACING: 3MHz
LOWER: –78.27dB
UPPER: –78.50dB
ADJACENT CHANNEL
BANDWIDTH: 3.84MHz
SPACING: 10MHz
LOWER: –81.42dB
UPPER: –81.87dB
Figure 24. Typical ACLR for Wideband CDMA
Rev. C | Page 15 of 64
AD9957
Data Sheet
MODES OF OPERATION
OVERVIEW
The AD9957 has three basic operating modes.
than that of the DAC. An internal chain of rate interpolation
filters the user data and upsamples to the DAC sample rate.
Combined, the filters provide for programmable rate interpola-
tion while suppressing spectral images and retaining the original
baseband spectrum.
•
•
•
Quadrature modulation (QDUC) mode (default)
Interpolating DAC mode
Single tone mode
QDUC mode employs both the DDS and the rate interpolation
filters. In this case, two parallel banks of rate interpolation
filters allow baseband processing of in-phase and quadrature
(I/Q) signals with the DDS providing the carrier signal to be
modulated by the baseband signals. A detailed block diagram of
the AD9957 is shown in Figure 25.
The active mode is selected via the operating mode bits in
Control Function Register 1 (CFR1). Single tone mode allows
the device to operate as a sinusoidal generator with the DDS
driving the DAC directly.
Interpolating DAC mode bypasses the DDS, allowing the user
to deliver baseband data to the device at a sample rate lower
The inverse sinc filter is available in all three modes.
AD9957
I
18
16
8
AUX
DAC
8-BIT
DAC GAIN
DDS
IS
DAC_RSET
18
I/Q IN
θ
QS
cos (ωt+θ)
ω
IOUT
IOUT
DAC
14-BIT
16
18
sin (ωt+θ)
CLOCK
OUTPUT
SCALE
FACTOR
Q
REFCLK_OUT
OSK
÷2
SYSCLK
PDCLK
REF_CLK
REF_CLK
PARALLEL DATA
TIMING AND CONTROL
INTERNAL CLOCK TIMING AND CONTROL
PLL
TxENABLE
XTAL_SEL
POWER
FTW
PW
SERIAL I/O
PORT
PROGRAMMING
REGISTERS
RAM
DOWN
CONTROL
2
2
3
I Q IS QS
Figure 25. Detailed Block Diagram
Rev. C | Page 16 of 64
Data Sheet
AD9957
The PROFILE and I/O_UPDATE pins are also synchronous to
the PDCLK.
QUADRATURE MODULATION MODE
A block diagram of the AD9957 operating in QDUC mode is
shown in Figure 26; grayed items are inactive. The parallel input
accepts 18-bit I- and Q-words in time-interleaved fashion. That
is, an 18-bit I-word is followed by an 18-bit Q-word, then the
next 18-bit I-word, and so on. One 18-bit I-word and one 18-bit
Q-word together comprise one internal sample. The data assem-
bler and formatter de-interleave the I- and Q-words so that each
sample propagates along the internal data pathway in parallel
fashion. Both I and Q data paths are active; the parallel data
clock (PDCLK) serves to synchronize the input of I/Q data to
the AD9957.
The DDS core provides a quadrature (sine and cosine) local
oscillator signal to the quadrature modulator, where the
interpolated I and Q samples are multiplied by the respective
phase of the carrier and summed together, producing a
quadrature modulated data stream. This data stream is routed
through the inverse sinc filter (optionally), and the output
scaling multiplier. Then it is applied to the 14-bit DAC to
produce the quadrature modulated analog output signal.
AD9957
I
18
16
8
AUX
DAC
8-BIT
DAC GAIN
DDS
IS
DAC_RSET
18
I/Q IN
θ
QS
cos (ωt+θ)
ω
IOUT
IOUT
DAC
14-BIT
16
18
sin (ωt+θ)
CLOCK
OUTPUT
SCALE
FACTOR
Q
REFCLK_OUT
OSK
÷2
SYSCLK
PDCLK
REF_CLK
REF_CLK
PARALLEL DATA
TIMING AND CONTROL
INTERNAL CLOCK TIMING AND CONTROL
PLL
TxENABLE
XTAL_SEL
POWER
FTW
PW
SERIAL I/O
PORT
PROGRAMMING
REGISTERS
RAM
DOWN
CONTROL
2
2
3
I Q IS QS
Figure 26. Quadrature Modulation Mode
Rev. C | Page 17 of 64
AD9957
Data Sheet
The Blackfin interface includes an additional pair of half-band
filters in both I and Q signal paths (not shown explicitly in the
diagram). The two half-band filters increase the interpolation
of the baseband data by a factor of four, relative to the normal
QDUC mode.
BLACKFIN INTERFACE (BFI) MODE
A subset of the QDUC mode is the Blackfin interface (BFI)
mode, shown in Figure 27; grayed items are inactive. In this
mode, a separate I and Q serial bit stream is applied to the
baseband data port instead of parallel data-words. The two
serial inputs provide for 16-bit I- and Q-words (unlike the
18-bit words in normal QDUC mode). The serial bit streams
are delivered to the Blackfin interface. The Blackfin interface
converts the 16-bit serial data into 16-bit parallel data to
propagate down the signal processing chain.
The synchronization of the serial data occurs through the
PDCLK signal. In BFI mode, the PDCLK signal is effectively
the bit clock for the serial data.
Note that the system clock is limited to 750 MHz in BFI mode.
AD9957
I
18
16
8
AUX
DAC
8-BIT
DAC GAIN
DDS
IS
DAC_RSET
2
I/Q IN
θ
QS
cos (ωt+θ)
ω
IOUT
IOUT
DAC
14-BIT
16
18
sin (ωt+θ)
CLOCK
OUTPUT
SCALE
FACTOR
Q
REFCLK_OUT
OSK
÷2
SYSCLK
PDCLK
REF_CLK
REF_CLK
PARALLEL DATA
TIMING AND CONTROL
INTERNAL CLOCK TIMING AND CONTROL
PLL
TxENABLE
XTAL_SEL
POWER
FTW
PW
SERIAL I/O
PORT
PROGRAMMING
REGISTERS
RAM
DOWN
CONTROL
2
2
3
I Q IS QS
Figure 27. Quadrature Modulation Mode, Blackfin Interface
Rev. C | Page 18 of 64
Data Sheet
AD9957
No modulation takes place in the interpolating DAC mode;
INTERPOLATING DAC MODE
therefore, the spectrum of the data supplied at the parallel port
remains at baseband. However, a sample rate conversion takes
place based on the programmed interpolation rate. The inter-
polation hardware processes the signal, effectively performing
an oversample with a zero-stuffing operation. The original
input spectrum remains intact and the images that otherwise
would occur from the sample rate conversion process are
suppressed by the interpolation signal chain.
A block diagram of the AD9957 operating in interpolating DAC
mode is shown in Figure 28; grayed items are inactive. In this
mode, the Q data path, DDS, and modulator are all disabled; only
the I data path is active.
As in quadrature modulation mode, the PDCLK pin functions
as a clock, synchronizing the input of data to the AD9957.
AD9957
I
18
16
8
AUX
DAC
8-BIT
DAC GAIN
DDS
IS
DAC_RSET
18
I/Q IN
θ
QS
cos (ωt+θ)
ω
IOUT
IOUT
DAC
14-BIT
16
18
sin (ωt+θ)
CLOCK
Q
OUTPUT
SCALE
FACTOR
REFCLK_OUT
OSK
÷2
SYSCLK
PDCLK
REF_CLK
REF_CLK
PARALLEL DATA
TIMING AND CONTROL
INTERNAL CLOCK TIMING AND CONTROL
PLL
TxENABLE
XTAL_SEL
POWER
FTW
PW
SERIAL I/O
PORT
PROGRAMMING
REGISTERS
RAM
DOWN
CONTROL
2
2
3
I
Q
IS QS
Figure 28. Interpolating DAC Mode
Rev. C | Page 19 of 64
AD9957
Data Sheet
cosine or sine output of the DDS. The sinusoid at the DDS
SINGLE TONE MODE
output can be scaled using a 14-bit amplitude scale factor (ASF)
and optionally routed through the inverse sinc filter.
A block diagram of the AD9957 operating in single tone mode
is shown in Figure 29; grayed items are inactive. In this mode,
both I and Q data paths are disabled from the 18-bit parallel
data port up to, and including, the modulator. The internal
DDS core produces a single frequency signal based on the
programmed tuning word. The user may select either the
Single tone mode offers the output shift keying (OSK) function.
It provides the ability to ramp the amplitude scale factor between
zero and an arbitrary preset value over a programmable time
interval.
AD9957
I
18
16
8
AUX
DAC
8-BIT
DAC GAIN
DDS
IS
DAC_RSET
10
I/Q IN
θ
QS
cos (ωt+θ)
ω
IOUT
IOUT
DAC
14-BIT
16
18
sin (ωt+θ)
CLOCK
OUTPUT
SCALE
FACTOR
Q
REFCLK_OUT
OSK
÷2
SYSCLK
PDCLK
REF_CLK
REF_CLK
PARALLEL DATA
TIMING AND CONTROL
INTERNAL CLOCK TIMING AND CONTROL
PLL
TxENABLE
XTAL_SEL
POWER
FTW
PW
SERIAL I/O
PORT
PROGRAMMING
REGISTERS
RAM
DOWN
CONTROL
2
2
3
I
Q
IS QS
Figure 29. Single Tone Mode
Rev. C | Page 20 of 64
Data Sheet
AD9957
SIGNAL PROCESSING
For a better understanding of the operation of the AD9957, it
is helpful to follow the signal path in quadrature modulation
mode from the parallel data port to the output of the DAC,
examining the function of each block (see Figure 26).
TRANSMIT ENABLE PIN (TxENABLE)
The AD9957 accepts a user-generated signal applied to the
TxENABLE pin that gates the user supplied data. Polarity of
the TxENABLE pin is set using the TxENABLE invert bit (see
the Register Map section for details). When TxENABLE is true,
the device latches data into the device on the expected edge of
PDCLK (based on the PDCLK invert bit). When TxENABLE
is false, the device ignores the data supplied to the port, even
though the PDCLK may continue to operate. Furthermore,
when the TxENABLE pin is held false, then the device either
forces the 18-bit data-words to Logic 0s, or it retains the last
value present on the data port prior to TxENABLE switching
to the false state (see the data assembler hold last value bit in
the Register Map section).
The internal system clock (SYSCLK) signal that generates from
the timing source provided to the REF_CLK pins provides all
timing within the AD9957.
PARALLEL DATA CLOCK (PDCLK)
The AD9957 generates a signal on the PDCLK pin, which is a
clock signal that runs at the sample rate of the parallel data port.
PDCLK serves as a data clock for the parallel port in QDUC
and interpolating DAC modes; in BFI mode, it is a bit clock.
Normally, the device uses the rising edges on PDCLK to latch
the user-supplied data into the data port. Alternatively, the
PDCLK Invert bit selects the falling edges as the active edges.
Furthermore, the PDCLK enable bit is used to switch off the
PDCLK signal. Even when the output signal is turned off via the
PDCLK enable bit, PDCLK continues to operate internally. The
device uses PDCLK internally to capture parallel data. Note that
PDCLK is Logic 0 when disabled.
Alternatively, rather than operating the TxENABLE pin as a
gate for framing bursts of data, it can be driven with a clock
signal operating at the parallel port data rate. When driven by
a clock signal, the transition from the false to true state must
meet the required setup and hold times on each cycle to ensure
proper operation.
In QDUC mode, on the false-to-true edge of TxENABLE, the
device is ready to receive the first I-word. The first I-word is
latched into the device coincident with the active edge of PDCLK.
The next active edge of PDCLK latches in a Q-word, and so on,
until TxENABLE is returned to a static false state. The user may
reverse the ordering of the I- and Q-words via the Q-First Data
Pairing bit. Furthermore, the user must ensure that an even
number of data words are delivered to the device as it must
capture both an I- and a Q-word before the data is processed
along the signal chain.
In QDUC mode, the AD9957 expects alternating I- and Q-
data-words at the parallel port (see Figure 31). Each active edge
of PDCLK captures one 18-bit word; therefore, there are two
PDCLK cycles per I/Q pair. In BFI mode, the AD9957 expects
two serial bit streams, each segmented into 16-bit words with
PDCLK indicating each new bit. In either case, the output clock
rate is fPDCLK as explained in the Input Data Assembler section.
In QDUC applications that require a consistent timing relation-
ship between the internal SYSCLK signal and the PDCLK signal,
the PDCLK rate control bit is used to slightly alter the operation
of PDCLK. When this bit is set, the PDCLK rate is reduced by
a factor of two. This causes rising edges on PDCLK to latch
incoming I-words and falling edges to latch incoming Q-words.
Again, the edge polarity assignment is reversible via the PDCLK
Invert bit.
In interpolating DAC mode, TxENABLE operation is similar to
QDUC mode, but without the need for I/Q data pairing; the
even-number-of-PDCLK-cycles rule does not apply.
In BFI mode, operation of the TxENABLE pin is similar except
that instead of the false-to-true edge marking the first I-word,
it marks the first I and Q bits in a serial frame. The user must
ensure that all 16-bits of a serial frame are delivered because the
device must capture a full 16-bit I- and Q-word before the data
is processed along the signal chain.
The timing relationships between TxENABLE, PDCLK, and
DATA are shown in Figure 30, Figure 31, and Figure 32.
Rev. C | Page 21 of 64
AD9957
Data Sheet
TxENABLE
tDS
tDH
PDCLK
tDS
I
I
I
I
3
I
I
D<17:0>
0
1
2
K – 1
K
tDH
Figure 30. 18-Bit Parallel Port Timing Diagram—Interpolating DAC Mode
TxENABLE
tDS
tDH
PDCLK
tDS
I
Q
I
Q
1
I
Q
N
D<17:0>
0
0
1
N
tDH
Figure 31. 18-Bit Parallel Port Timing Diagram—Quadrature Modulation Mode
TxENABLE
PDCLK
I DATA
Q DATA
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
I
16n – 1
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
Q
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Q
16n – 1
Figure 32. Dual Serial I/Q Bit Stream Timing Diagram, BFI Mode
When the PDCLK rate control bit is active in QDUC mode,
however, the frequency of PDCLK becomes
INPUT DATA ASSEMBLER
The input to the AD9957 is an 18-bit parallel data port in
QDUC mode or interpolating DAC mode. In BFI mode, it
operates as a dual serial data port.
fSYSCLK
fPDCLK
=
with PDCLK rate control active
4R
In QDUC mode, it is assumed that two consecutive 18-bit
words represent the real (I) and imaginary (Q) parts of a
complex number of the form, I + jQ. The 18-bit words are
supplied to the input of the AD9957 at a rate of
In the interpolating DAC mode, the rate of PDCLK is the same
as QDUC mode with the PDCLK rate control bit active, that is,
fSYSCLK
4R
fPDCLK
=
for interpolating DAC mode
fSYSCLK
2R
fPDCLK
=
for QDUC mode
In BFI mode, the 18-bit parallel input converts to a dual serial
input that is, one pin is assigned as the serial input for the I-words
and one pin is assigned as the serial input for the Q-words. The
other 16 pins are not used. Furthermore, each I- and Q-word
has a 16-bit resolution. fPDCLK is the bit rate of the I- and Q-data
streams and is given by
where:
SYSCLK (for all of the PDCLK equations in this section) is the
f
sample rate of the DAC.
R (for all of the PDCLK equations in this section) is the
interpolation factor of the programmable interpolation filter.
fSYSCLK
R
fPDCLK
=
for BFI mode
Rev. C | Page 22 of 64
Data Sheet
AD9957
Encoding and pulse shaping of symbols must be implemented
before the data is presented to the input of the AD9957. Data
delivered to the input of the AD9957 may be formatted as either
twos complement or offset binary (see the Data Format bit in
Table 13). In BFI mode, the bit sequence order can be set to
either MSB-first or LSB-first (via the Blackfin Bit Order bit).
FIXED INTERPOLATOR (4×)
This block is a fixed 4× rate interpolator, implemented as a
cascade of two half-band filters. Together, the sampling rate
of these two filters increases by a factor of four while preserving
the spectrum of the baseband signal applied at the input. Both
are linear phase filters; virtually no phase distortion is intro-
duced within their pass bands. Their combined insertion loss
is 0.01 dB, preserving the relative amplitude of the input signal.
INVERSE CCI FILTER
The inverse cascaded comb integrator (CCI) filter predistorts
the data, compensating for the slight attenuation gradient imposed
by the CCI filter (see the Programmable Interpolating Filter
section). Data entering the first half-band filter occupies a maxi-
mum bandwidth of ½ fIQ as defined by Nyquist (where fIQ is the
sample rate at the input of the first half-band filter); see Figure 33.
The filters are designed to deliver a composite performance that
yields a usable pass band of 40% of the input sample rate. Within
that pass band, ripple does not exceed 0.002 dB peak-to-peak.
The stop band extends from 60% to 340% of the input sample
rate and offers a minimum of 85 dB attenuation. Figure 34 and
Figure 35 show the composite response of the two half-band filters.
If the CCI filter is used, the inband attenuation gradient can pose a
problem for applications requiring an extremely flat pass band.
For example, if the spectrum of the data supplied to the AD9957
occupies a significant portion of the ½ fDATA region, the higher
frequencies of the data spectrum are slightly more attenuated
than the lower frequencies (the worst-case overall droop from
f = 0 to ½ fDATA is <0.8 dB). The inverse CCI filter has a response
characteristic that is the inverse of the CCI filter response over
the ½ fIQ region.
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
INBAND
ATTENUATION
GRADIENT
0
0.5
1.0
1.5
2.0
fI
2.5
3.0
3.5
4.0
CCI FILTER RESPONSE
Figure 34. Half-Band 1 and Half-Band 2 Composite Response
(Frequency Scaled to Input Sample Rate of Half-Band 1)
0.010
0.008
0.006
0.004
0.002
0
f
4fIQ
fIQ
½fIQ
Figure 33. CCI Filter Response
–0.002
–0.004
–0.006
–0.008
–0.010
The product of the two responses yields an extremely flat
pass band ( 0.05 dB over the baseband Nyquist bandwidth)
eliminating the inband attenuation gradient introduced by the
CCI filter. The cost is a slight attenuation of the input signal
(approximately 0.5 dB for a CCI interpolation rate of 2, and
0.8 dB for higher interpolation rates).
0
0.1
0.2
0.3
0.4
0.5
fI
The inverse CCI filter can be bypassed using the appropriate bit
in the register map; it is automatically bypassed if the CCI inter-
polation rate is 1×. When bypassed, power to the stage turns off
to reduce power consumption.
Figure 35. Composite Pass-Band Detail
(Frequency Scaled to Input Sample Rate of Half-Band 1)
In BFI mode, there are two additional half-band filters resident,
yielding a total fixed interpolation factor of 16×. The extra BFI
filters use the same filter tap coefficient values as the QDUC
half-band filters, but their data pathway is 16 bits (instead of
18 bits as with the QDUC half-band filters). As such, baseband
quantization noise is higher in BFI mode.
Rev. C | Page 23 of 64
AD9957
Data Sheet
Knowledge of the frequency response of the half-band filters is
essential to understanding their impact on the spectral properties
of the input signal. This is especially true when using the quad-
rature modulator to upconvert a baseband signal containing
complex data symbols that have been pulse shaped.
response portion of the diagram to the right, as it must remain
aligned with the corresponding MfSYMBOL point on the frequency
axis of the raised cosine spectral diagram. However, if fIQ shifts
to the right, so does the half-band response, proportionally.
The result is that the raised cosine spectral mask always lies
within the flat portion (dc to 0.4 fIQ) of the pass band response
of the first half-band filter, regardless of the choice of α so long
as M > 2. Therefore, for M > 2, the first half-band filter has
absolutely no negative impact on the spectrum of the baseband
signal when raised cosine pulse shaping is employed. For the
case of M = 2, a problem can arise. This is highlighted by the
shaded area in the tail of the α = 1 trace on the raised cosine
spectral mask diagram. Notice that this portion of the raised
cosine spectral mask extends beyond the flat portion of the
half-band response and causes unwanted amplitude and phase
distortion as the signal passes through the first half-band filter.
To avoid this, simply ensure that α ≤ 0.6 when M = 2.
Consider that a complex symbol is represented by a real (I) and
an imaginary (Q) component, thus requiring two digital words
to represent a single complex sample of the form I + jQ. The
sample rate associated with a sequence of complex symbols is
referred to as fSYMBOL. If pulse shaping is applied to the symbols,
the sample rate must be increased by some integer factor, M
(a consequence of the pulse shaping process). This new sample
rate (fIQ) is related to the symbol rate by
f
IQ = MfSYMBOL
where fIQ is the rate at which complex samples must be supplied
to the input of the first half-band filter in both (I and Q) signal
paths. This rate should not be confused with the rate at which
data is supplied to the AD9957.
PROGRAMMABLE INTERPOLATING FILTER
The programmable interpolator is implemented as a low-pass
CCI filter. It is programmable by a 6-bit control word, giving a
range of 2× to 63× interpolation.
Typically, pulse shaping is applied to the baseband symbols via
a filter having a raised cosine response. In such cases, an excess
bandwidth factor (α, 0 ≤ α ≤ 1) is used to modify the bandwidth
of the data. For α = 0, the data bandwidth corresponds to fSYMBOL/2;
for α = 1, the data bandwidth extends to fSYMBOL. Figure 36 shows
the relationship between α, the bandwidth of the raised cosine
response, and the response of the first half-band filter.
The programmable interpolator is bypassed when programmed
for an interpolation factor of 1. When bypassed, power to the
stage is removed and the inverse CCI filter is also bypassed,
because its compensation is not needed.
The output of the programmable interpolator is the data from
the 4× interpolator further upsampled by the CCI filter, accord-
ing to the rate chosen by the user. This results in the upsampling of
the input data by a factor of 8× to 252× in steps of four.
TYPICAL SPECTRUM OF A RANDOM SYMBOL SEQUENCE
NYQUIST
BAND
WIDTH
The transfer function of the CCI interpolating filter is
f
)5
½fSYMBOL fSYMBOL
2
fSYMBOL
3
fSYMBOL
R − 1
∑ e
k = 0
(
−j 2π fk
H
(
f
)
=
(1)
RAISED COSINE
SPECTRAL MASK
where R is the programmed interpolation factor, and f is the
frequency normalized to fSYSCLK
.
SAMPLE RATE FOR
2× OVERSAMPLED
PULSE SHAPING
α = 1
α = 0
α = 0.5
Note that minimum R requirements exist depending on the
mode and frequency of fSYSCLK. The minimum R setting is
defined under the follo wing conditions.
f
½fSYMBOL fSYMBOL
2
fSYMBOL
4
fSYMBOL
QDUC Mode
HALF-BAND
FILTER
RESPONSE
If fSYSCLK is between 500 MSPS to 1 GSPS, then the minimum R is 2.
If fSYSCLK is less than 500 MSPS, then the minimum R is 1.
BFI Mode
INPUT SAMPLE
RATE OF FIRST
HALF-BAND
FILTER
INPUT SAMPLE
RATE OF FIRST
HALF-BAND
FILTER
f
0.4fIQ ½fIQ
fIQ
2fIQ
If fSYSCLK is between 500 MSPS to 750 MSPS, then the minimum
R is 3.
Figure 36. Effect of the Excess Bandwidth Factor (α)
If fSYSCLK is between 250 MSPS to 500 MSPS, then the minimum
R is 2.
The responses in Figure 36 reflect the specific case of M = 2 (the
interpolation factor for the pulse shaping operation). Increasing
Factor M shifts the location of the fIQ point on the half-band
If fSYSCLK is less than 250 MSPS, then the minimum R is 1.
Rev. C | Page 24 of 64
Data Sheet
AD9957
where the round() function means to round the result to the
QUADRATURE MODULATOR
nearest integer. For example, for fOUT = 41 MHz and fSYSCLK
=
The digital quadrature modulator stage shifts the frequency of
the baseband spectrum of the incoming data stream up to the
desired carrier frequency (a process known as upconversion).
122.88 MHz, then FTW = 1,433,053,867 (0x556AAAAB).
In single tone mode, the DDS frequency, phase, and amplitude
are all programmable via the serial I/O port. The amplitude
is controlled by means of a digital multiplier using a 14-bit
fractional scale value called the amplitude scale factor (ASF).
The LSB weight is 2−14, yielding a multiplier range of 0 to
0.99993896484375 (1 − 2−14). To bypass the ASF multiplier,
program the appropriate control register bit (see the details of
CFR2<24> in the Register Bit Descriptions section). When
bypassed, the ASF multiplier clocks are disabled to conserve
power. The phase offset is controlled by means of a digital adder
that uses a 14-bit offset value called the phase offset word (POW).
The adder is situated between the phase accumulator and the
angle-to-amplitude conversion logic in the DDS core. The adder
applies the POW to the instantaneous phase values produced by
the DDS phase accumulator. The adder is MSB aligned with the
phase accumulator yielding an LSB weight of 2−14 (which equates to
a resolution of ~0.022° or ~0.000383 radians). Both the ASF and
the POW are available for each of the eight profiles.
At this point, the baseband data, which was delivered to the
device at an I/Q sample rate of fIQ, has been upsampled to a rate
equal to the frequency of SYSCLK, making the data sampling
rate equal to the sampling rate of the carrier signal.
The frequency of the carrier signal is controlled by a direct
digital synthesizer (DDS). The DDS very precisely generates the
desired carrier frequency from the internal reference clock
(SYSCLK). The carrier is applied to the I and Q multipliers in
quadrature fashion (90° phase offset) and summed, yielding a
data stream that represents the quadrature modulated carrier.
The modulation is performed digitally, avoiding the phase
offset, gain imbalance, and crosstalk issues commonly associated
with analog modulators. Note that the modulated, so-called
signal is a number stream sampled at the rate of SYSCLK, the
same rate at which the DAC is clocked.
The orientation of the modulated signal with respect to the
carrier is controlled by a spectral invert bit. This bit resides in
each of the eight profile registers. By default, the time domain
output of the quadrature modulator takes the form
INVERSE SINC FILTER
The sampled carrier data stream is the input to the digital-to-
analog converter. The DAC output spectrum is shaped by the
characteristic sin(x)/x (or sinc) envelope, due to the intrinsic
zero-order hold effect associated with DAC-generated signals.
The shape of the sinc envelope is well known and can be
compensated for. This compensation is provided by the inverse
sinc filter preceding the DAC.
I(t) × cos(ωt) − Q(t) × sin(ωt)
(2)
When the spectral invert bit is asserted, it becomes
I(t) × cos(ωt) + Q(t) × sin(ωt)
(3)
DDS CORE
The inverse sinc filter is implemented as a digital FIR filter. Its
response characteristic very nearly matches the inverse of the
sinc envelope, as shown in Figure 37 (along with the sinc
envelope for comparison).
The direct digital synthesizer (DDS) block generates sine
and/or cosine signals. In single tone mode, the DDS generates
either a digital sine or cosine waveform based on the select DDS
sine output bit. In QDUC mode, the DDS generates the quadra-
ture carrier reference signal that digitally modulates the I/Q
baseband signal.
The inverse sinc filter is enabled through a bit in the register
map. The filter tap coefficients are listed in Table 4. The filter
predistorts the data prior to its arrival at the DAC to compensate
for the sinc envelope that otherwise distorts the spectrum.
The DDS output frequency is tuned using registers accessed via
the serial I/O port. This allows for both precise tuning and
instantaneous changing of the carrier frequency.
When the inverse sinc filter is enabled, it introduces a ~3.0 dB
insertion loss. The inverse sinc compensation is effective for
output frequencies up to 40% (nominally) of the DAC sample rate.
The equation relating output frequency (fOUT) of the DDS to the
frequency tuning word (FTW) and the system clock (fSYSCLK) is
Table 4. Inverse Sinc Filter Tap Coefficients
FTW
Tap No.
Tap Value
Tap No.
fOUT
=
f
(4)
SYSCLK
232
1
2
3
4
−35
+134
−562
+6729
7
6
5
4
where FTW is a decimal number from 0 to 2,147,483,647 (231 − 1).
Solving for FTW yields
32
fOUT
fSYSCLK
FTW = round 2
(5)
Rev. C | Page 25 of 64
AD9957
Data Sheet
14-BIT DAC
In Figure 37, it can be seen that the sinc envelope introduces a
frequency dependent attenuation that can be as much as 4 dB at
the Nyquist frequency (half of the DAC sample rate). Without
the inverse sinc filter, the DAC output also suffers from the
frequency dependent droop of the sinc envelope. The inverse
sinc filter effectively flattens the droop to within 0.05 dB as
shown in Figure 38, which shows the corrected sinc response
with the inverse sinc filter enabled.
The AD9957 incorporates an integrated 14-bit current-output
DAC. The output current is delivered as a balanced signal using
two outputs. The use of balanced outputs reduces the amount of
common-mode noise at the DAC output, increasing signal-to-
noise ratio. An external resistor (RSET) connected between the
DAC_RSET pin and AGND establishes a reference current. The
full-scale output current of the DAC (IOUT) is a scaled version of
the reference current (see the Auxiliary DAC section that
follows).
1
SINC
0
Proper attention should be paid to the load termination to keep
the output voltage within the specified compliance range, as
voltages developed beyond this range cause excessive distortion
and can damage the DAC output circuitry.
–1
–2
Auxiliary DAC
The full-scale output current of the main DAC (IOUT) is con-
trolled by an 8-bit auxiliary DAC. An 8-bit code word stored in
the appropriate register map location sets IOUT according to the
following equation:
INVERSE
SINC
–3
–4
0
0.1
0.2
0.3
0.4
0.5
86.4
CODE
FREQUENCY RELATIVE TO DAC SAMPLE RATE
IOUT
=
1+
(6)
RSET
96
Figure 37. Sinc and Inverse Sinc Responses
–2.8
–2.9
–3.0
–3.1
where:
SET is the value of the RSET resistor (in ohms).
CODE is the 8-bit value supplied to the auxiliary DAC (default
R
is 127).
For example, with RSET = 10,000 and CODE = 127, IOUT = 20.07 mA.
COMPENSATED RESPONSE
0
0.1
0.2
0.3
0.4
0.5
FREQUENCY RELATIVE TO DAC SAMPLE RATE
Figure 38. DAC Response with Inverse Sinc Compensation
OUTPUT SCALE FACTOR (OSF)
In QDUC and interpolating DAC modes, the output amplitude
is controlled using an 8-bit digital multiplier. The 8-bit multiplier
value is called the output scale factor (OSF) and is programmed
via the appropriate control registers. It is available for each of
the eight profiles. The LSB weight is 2−7, which yields a multiplier
range of 0 to 1.9921875 (2 − 2−7). The gain extends to nearly a
factor of 2 to provide a means to overcome the intrinsic loss
through the modulator when operating in the quadrature
modulation mode.
In interpolating DAC mode, the OSF should not be programmed
to exceed unity, as clipping can result. Programming the 8-bit
multiplier to unity gain (0x80) bypasses the stage and reduces
power consumption.
Rev. C | Page 26 of 64
Data Sheet
AD9957
RAM CONTROL
Q-channel bits. In playback mode, when driving data directly
into the baseband signal chain, the 16-bit data-words are
RAM OVERVIEW
The AD9957 has an integrated 1024 × 32-bit RAM. This RAM
is only accessible when the AD9957 is operating in QDUC or
interpolating DAC mode. The RAM has two fundamental
modes of operation: data entry/retrieve mode and playback
mode. The mode is selected by programming the RAM Enable
bit in CFR1 via the serial I/O port.
considered to be signed (that is, twos complement) values. The
16-bit I-and Q-words are MSB aligned with the 18-bit I and Q
baseband data path. The two remaining LSBs of each 18-bit
baseband channel are driven by the MSB of the respective
channel. This ensures correct polarity coding when the 16-bit I
and Q data from the RAM translates into 18-bit words for the
baseband signal chain. Alternatively, when the RAM is driving
the baseband scaling multipliers in playback mode, the RAM
data is considered to represent unsigned, fractional values with a
Data entry/retrieve mode is used to load or read back the RAM
contents via the serial I/O port. Playback mode is used to deliver
RAM data to one of two internal destinations: the baseband
scaling multipliers (see Figure 25, the IS and QS labels) or the
baseband signal chain (see Figure 25, the I and Q labels). In
both cases, the RAM can be used to apply an arbitrary, time-
varying waveform to the selected destination. A block diagram
of the RAM and its control elements is shown in Figure 39.
range of 0 to 1 − 2−16
.
RAM SEGMENT REGISTERS
Two dedicated registers (RAM Segment Register 0 and RAM
Segment Register 1) control the operation of the RAM. Each
contains the following:
The external parallel data port is disabled when the baseband
signal chain serves as the RAM playback destination.
•
•
•
•
10-bit start address word
10-bit end address word
16-bit address step rate word
3-bit RAM playback mode word
RT
3
RAM MODE
16
10
ADDRESS STEP RATE
START ADDRESS
END ADDRESS
RAM
SEGMENT
REGISTERS
10
When programming these registers, the user must ensure that
the end address is greater than the start address.
DDS CLOCK
BASEBAND DATA CLOCK
With the RAM segment registers, the user can arbitrarily partition
the RAM into two independent memory segments. The segment
boundaries are specified with the start and end address words
in each RAM segment register. The playback rate is controlled
by the address step rate word (only meaningful when the base-
band scaling multipliers serve as the playback destination). If the
baseband signal chain serves as the RAM playback destination,
the 16-bit address step rate words must be set to 1. The playback
mode of the RAM is controlled via the RAM playback mode word.
SDIO
CLK
U/D
Q
32
32
10
SDO
STATE
MACHINE
RAM
SCLK
I/O_RESET
CS
UP/DOWN COUNTER
I CHANNEL
I
16
IS
(MSBs)
Q
Q CHANNEL
16
QS
(LSBs)
Figure 39. RAM Block Diagram
RAM STATE MACHINE
In Figure 39, the serial I/O port is used to program the contents
of the two RAM segment registers as well as to load and retrieve
the RAM contents. The state machine takes care of incrementing
or decrementing the RAM address locations and controlling the
timing of the RAM address and data for proper operation. The
I-channel and Q-channel multiplexers route RAM data to base-
band scaling multipliers (IS/QS) or directly to the baseband
signal chain (I/Q) when the RAM is used in playback mode.
The state of the RAM playback destination bit determines the
destination of the RAM data during playback.
The state machine acts as an address generator for the RAM. It
is clocked by either the serial I/O port (when the RAM is operating
in the load/retrieve mode) or the baseband data clock (when
the RAM is in playback mode). The state machine uses the
RAM mode bits of the active RAM segment register to establish
the proper sequence through the specified address range.
RAM TRIGGER (RT) PIN
The RAM state machine monitors the RT pin for logic state tran-
sitions. Any state transition triggers the state machine into action.
An I/O update (or a profile change) is necessary to enact a state
change of the RAM enable or RAM playback destination bits, or
any of the RAM segment register bits.
The direction of the logic state transition on the RT pin deter-
mines which RAM segment register the state machine uses for
playback instructions. RAM Segment Register 0 is used if the
state machine detects a 0-to-1 transition; RAM Segment Register 1
is used if a 1-to-0 transition is detected.
The 32-bit RAM data bus is partitioned so that the 16 MSBs are
designated as I-channel bits and the 16 LSBs are designated as
Rev. C | Page 27 of 64
AD9957
Data Sheet
rate when the playback destination is the baseband scaling
multipliers.
LOAD/RETRIEVE RAM OPERATION
Loading or retrieving the RAM contents is a three-step process.
Although RAM load/retrieve operations via the serial I/O port
take precedence over playback, it is recommended that the user
not attempt RAM access via the serial I/O port when the RAM
enable bit is set.
1. Program the RAM segment registers with start and end
addresses defining the boundaries of each independent
RAM segment.
2. Toggle the RT pin with the appropriate transition to select
the desired RAM segment register.
Figure 41 is a block diagram showing the functional compo-
nents used for RAM playback operation when the internal
destination is the baseband scaling multipliers.
3. Using the serial I/O port, write (or read) the address range
specified by the selected RAM segment register.
RT
3
RAM MODE
Figure 40 shows the RAM block diagram when used for loading
or retrieve operations.
16
10
ADDRESS STEP RATE
START ADDRESS
END ADDRESS
RAM
SEGMENT
REGISTERS
10
DDS CLOCK
RT
3
BASEBAND DATA CLOCK
RAM MODE
16
10
ADDRESS STEP RATE
START ADDRESS
END ADDRESS
RAM
SEGMENT
REGISTERS
10
SDIO
CLK
U/D
Q
32
32
10
SDO
STATE
MACHINE
RAM
DDS CLOCK
SCLK
I/O_RESET
CS
BASEBAND DATA CLOCK
UP/DOWN COUNTER
I CHANNEL
I
16
SDIO
CLK
IS
U/D
Q
32
32
10
SDO
STATE
MACHINE
(MSBs)
RAM
SCLK
I/O_RESET
CS
Q
Q CHANNEL
16
QS
UP/DOWN COUNTER
I CHANNEL
I
(LSBs)
16
NOTES
IS
1. NONESSENTIAL FUNCTIONAL COMPONENTS ARE RENDERED IN GRAY.
(MSBs)
Q
Figure 41. RAM Playback to Baseband Scaling Multipliers
Q CHANNEL
16
QS
(LSBs)
During playback to the baseband scaling multipliers, the
address step rate word in the active RAM segment register sets
the rate at which RAM data samples are delivered to the
multipliers. The following equations define the RAM sample
rate and sample interval (Δt):
NOTES
1. NONESSENTIAL FUNCTIONAL COMPONENTS ARE RENDERED IN GRAY.
Figure 40. RAM Load/Retrieve Operation
During a load or retrieve operation, the state machine controls
an up/down counter to step through the required RAM locations.
The counter is synchronized with the serial I/O port so that the
serial/parallel conversion of the 32-bit words is correctly timed
with the generation of the appropriate RAM address to properly
execute the desired read or write operation. The up/down
counter always increments through the address range during
serial I/O port operations.
fSYSCLK
RAM SampleRate =
4RM
4RM
∆t =
fSYSCLK
where:
R is the rate interpolation factor for the CCI filter.
M is the 16-bit value of the address step rate word stored in the
active RAM segment register.
Because the RAM segment registers are completely independent,
it is possible to define overlapping address ranges. However,
doing so causes the overlapping address locations to be over-
written by the most recent write operation. It is recommended
that the user avoid defining overlapping address ranges.
If the RAM enable bit is set and the baseband scaling multi-
pliers are selected as the playback destination, then assertion
of an I/O update or profile change causes the multipliers to be
driven with a static value of zero. A subsequent state change on
the RT pin causes the multipliers to be driven by the data played
back from the RAM instead of the static zero value.
RAM PLAYBACK OPERATION
When the RAM has been loaded, it can be used for playback
operation. The destination of the playback data is selected via
the RAM playback destination bit. The active RAM segment
register is selected by the appropriate transition of the RT pin.
The active RAM segment register directs the internal state
machine by defining the RAM address range occupied by the
data and the RAM playback mode. It also defines the playback
Figure 42 is a block diagram showing RAM playback operation
when the internal destination is the baseband data path. During
playback to the baseband data path, the state machine increments/
decrements the RAM address at the baseband data rate (the
address step rate must be set to 1).
Rev. C | Page 28 of 64
Data Sheet
AD9957
RT
RAM Ramp-Up Mode
3
RAM MODE
16
10
ADDRESS STEP RATE
START ADDRESS
END ADDRESS
RAM
SEGMENT
REGISTERS
In ramp-up mode, upon assertion of an I/O update or a state
change on the RT pin, the RAM begins playback operation
using the parameters programmed into the selected RAM seg-
ment register. Data is extracted from RAM over the specified
address range contained in the start address and end address of
the active RAM segment register. The data is delivered at the
appropriate rate and to the destination as specified by the RAM
playback destination bit.
10
DDS CLOCK
BASEBAND DATA CLOCK
SDIO
CLK
U/D
Q
32
32
10
SDO
STATE
MACHINE
RAM
SCLK
I/O_RESET
CS
UP/DOWN COUNTER
I CHANNEL
I
16
IS
The playback rate is governed by the timer internal to the RAM
state machine and its period (Δt) is determined by the state of the
RAM playback destination bit as detailed in the RAM playback
operation section.
(MSBs)
Q
Q CHANNEL
16
QS
(LSBs)
NOTES
1. NONESSENTIAL FUNCTIONAL COMPONENTS ARE RENDERED IN GRAY.
The internal state machine begins extracting data from the
RAM at the start address and continues to extract data until it
reaches the end address. Upon reaching this address, the state
machine halts.
Figure 42. RAM Playback to Baseband Data Path
OVERVIEW OF RAM PLAYBACK MODES
The RAM is operational in any one of four different
playback modes.
A graphic representation of the ramp-up mode appears in
Figure 43. The upper trace shows the progression of the RAM
address from the start address to the end address for the active
RAM segment register. The address value advances by one with
each timeout of the timer internal to the state machine. The circled
numbers indicate specific events, explained as follows:
•
•
•
•
Ramp-up
Bidirectional ramp
Continuous bidirectional ramp
Continuous recirculate
RAM playback is only functional when the AD9957 is pro-
grammed for either the QDUC or interpolating DAC mode.
Event 1—an I/O update or state transition on the RT pin. This
event initializes the state machine to the start address of the active
RAM segment register.
The RAM playback mode is selected via the 3-bit RAM play-
back mode word located in each of the RAM segment registers.
Thus, the RAM playback mode is segment dependent. The
RAM playback mode bits are detailed in Table 5.
Event 2—the state machine reaches the end address of the active
RAM segment register and halts.
Table 5. RAM Playback Modes
RAM Playback Mode
1 PDCLK CYCLE
OR
M DDS CLOCK CYCLES
Bits<2:0>
RAM Playback Mode
Ramp-up
001
010
Bidirectional ramp
Δ
t
011
Continuous bidirectional
ramp
Continuous recirculate
Not Valid
END ADDRESS
RAM
ADDRESS
100
1
000, 101, 110, 111
START ADDRESS
The continuous bidirectional ramp and continuous recirculate
modes are not available when the baseband scaling multipliers
serve as the destination of RAM playback.
I/O_UPDATE OR
RT TRANSITION
1
2
Figure 43. Ramp-Up Timing Diagram
Rev. C | Page 29 of 64
AD9957
Data Sheet
A Logic 1 to Logic 0 transition on the RT pin instructs the state
machine to switch to RAM Segment Register 1 and to decrement
through the address range starting with the end address. As
long as the RT pin remains Logic 0, the state machine continues
to play back the RAM data until it reaches the start address, at
which point the state machine halts.
RAM Bidirectional Ramp Mode
This mode is unique in that the RAM segment playback mode
word of both RAM segment registers must be programmed for
RAM bidirectional ramp mode.
In bidirectional ramp mode, upon assertion of an I/O update,
the RAM readies for playback operation using the parameters
programmed into RAM Segment Register 0. The data is deliv-
ered at the appropriate rate and to the destination as specified
by the RAM playback destination bit.
It is important to note that RAM Segment Register 1 is played
back in reverse order for bidirectional ramp mode. This must
be kept in mind when the RAM contents are loaded via the
serial I/O port when bidirectional ramp mode is the intended
playback mode.
The playback rate is governed by the timer that is internal to the
RAM state machine, and its period (Δt) is determined by the
state of the RAM playback destination bit as detailed in the
RAM Playback Operation section.
A graphic representation of the bidirectional ramp mode
appears in Figure 44. It demonstrates the action of the state
machine in response to the RT pin. If the RT pin changes states
before the state machine reaches the programmed start or end
address, the internal timer is restarted and the direction of the
address counter reversed.
Playback begins upon a 0 to 1 logic transition on the RT pin.
This instructs the state machine to increment through the
address range specified in RAM Segment Register 0 starting
with the start address. As long as the RT pin remains Logic 1,
the state machine continues to play back the RAM data until it
reaches the end address, at which point the state machine halts.
0
1
0
1
0
RAM SEGMENT
1 PDCLK CYCLE
OR
M DDS CLOCK CYCLES
END ADDRESS
NUMBER 0
Δt
RAM
ADDRESS
1
Δt
Δt
START ADDRESS NUMBER 0
END ADDRESS NUMBER 1
RAM
ADDRESS
Δt
Δt
START ADDRESS NUMBER 1
RT
PIN
I/O_UPDATE
1
2
3
4
5
6
7
8
Figure 44. Bidirectional Ramp Timing Diagram
Rev. C | Page 30 of 64
Data Sheet
AD9957
The circled numbers in Figure 44 indicate specific events,
explained as follows:
Event 5—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0,
resets the internal timer, and begins incrementing the RAM
address counter.
Event 1—an I/O update or profile change activates the RAM
bidirectional ramp mode.
Event 6—the RT pin switches to Logic 0. The state machine
initializes to the end address of RAM Segment Register 1, resets
the internal timer, and begins decrementing the RAM address
counter.
Event 2—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0 and
begins incrementing the RAM address counter.
Event 3—the RT pin remained at Logic 1 long enough for the
state machine to reach the end address of RAM Segment
Register 0, at which point the address counter is halted.
Event 7—the RT pin remained at Logic 0 long enough for the
state machine to reach the start address of RAM Segment
Register 1, at which point the address counter is halted.
Event 4—the RT pin switches to Logic 0. The state machine
initializes to the end address of RAM Segment Register 1, resets
the internal timer, and begins decrementing the RAM address
counter.
Event 8—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0,
resets the internal timer, and begins incrementing the RAM
address counter.
Rev. C | Page 31 of 64
AD9957
Data Sheet
1 PDCLK CYCLE
OR
M DDS CLOCK CYCLES
Δ
t
END ADDRESS
RAM
ADDRESS
1
Δ
t
START ADDRESS
I/O_UPDATE OR
RT TRANSITION
1
2
3
Figure 45. Continuous Bidirectional Ramp Timing Diagram
RAM Continuous Bidirectional Ramp Mode
Note that a change in state of the RT pin aborts the current
waveform and the newly selected RAM segment register is used
to initiate a new waveform.
In continuous bidirectional ramp mode, upon assertion of an
I/O update or a state change on the RT pin, the RAM begins
playback operation using the parameters programmed into the
selected RAM segment register. Data is extracted from RAM
over the specified address range contained in the start address
and end address. The data is delivered at the appropriate rate
and to the destination as specified by the RAM playback
destination bit.
A graphic representation of the continuous bidirectional ramp
mode is shown in Figure 45. The circled numbers in Figure 45
indicate specific events, explained as follows:
Event 1—an I/O update or state change on the RT pin has
activated the RAM continuous bidirectional ramp mode. The
state machine initializes to the start address of the active RAM
segment register. The state machine begins incrementing
through the specified address range.
The playback rate is governed by the timer internal to the RAM
state machine and its period (Δt) is determined by the state of
the RAM playback destination bit as detailed in the RAM
Playback Operation section.
Event 2—the state machine reaches the end address of the active
RAM segment register.
After initialization, the internal state machine begins extracting
data from the RAM at the start address of the active RAM segment
register and increments the address counter until it reaches the
end address, at which point the state machine reverses the direc-
tion of the address counter and begins decrementing through
the address range. Whenever one of the terminal addresses is
reached, the state machine reverses the address counter; the
process continues indefinitely.
Event 3—the state machine reaches the start address of the
active RAM segment register.
The continuous bidirectional ramp continues indefinitely until
the next I/O update or state change on the RT pin.
Rev. C | Page 32 of 64
Data Sheet
AD9957
1 PDCLK CYCLE
OR
M DDS CLOCK CYCLES
Δ
t
END ADDRESS
RAM ADRESS
1
START ADDRESS
I/O_UPDATE OR
RT TRANSITION
1
2
3
4
5
Figure 46. Continuous Recirculate Timing Diagram
active RAM segment register and causes the state machine to
begin incrementing the address counter at the appropriate rate.
RAM Continuous Recirculate Mode
The continuous recirculate mode mimics ramp-up mode,
except that when the state machine reaches the end address of
the active RAM segment register, it does not halt. Instead, the
next timeout of the internal timer causes the state machine to
jump to the start address of the active RAM segment register.
This process continues indefinitely until an I/O update or state
change on the RT pin. A state change on the RT pin aborts the
current waveform and the newly selected RAM segment register
initiates a new waveform.
Event 2—the state machine reaches the end address of the active
RAM segment register.
Event 3—the state machine switches to the start address of the
active RAM segment register. The state machine continues to
increment the address counter.
Event 4—the state machine again reaches the end address of the
active RAM segment register.
A graphic representation of the continuous recirculate mode is
shown in Figure 46.
Event 5—the state machine switches to the start address of the
active RAM segment register. The state machine continues to
increment the address counter.
The circled numbers in Figure 46 indicate specific events, which
are explained as follows:
Event 4 and Event 5 repeat until an I/O update or state change
occurs on the RT pin.
Event 1—an I/O update or state change on the RT pin occurs.
This initializes the state machine to the start address of the
Rev. C | Page 33 of 64
AD9957
Data Sheet
CLOCK INPUT (REF_CLK)
REFCLK OVERVIEW
Table 6. REFCLK_OUT Buffer Control
The AD9957 supports a number of options for producing the
internal SYSCLK signal (that is, the DAC sample clock) via the
CFR3<29:28>
REFCLK_OUT Buffer
00
01
10
11
Disabled
REF_CLK
REF_CLK/
input pins. The REF_CLK input can be
Low output current
Medium output current
High output current
driven directly from a differential or single-ended source, or it
can accept a crystal connected across the two input pins. There
is also an internal phase-locked loop (PLL) multiplier that can
be independently enabled. A block diagram of the REF_CLK
functionality is shown in Figure 47. The various input configu-
rations are controlled by means of the XTAL_SEL pin and
control bits in the CFR3 register. Figure 47 also shows how the
CFR3 control bits are associated with specific functional blocks.
CRYSTAL DRIVEN REF_CLK
When using a crystal at the REF_CLK input, the resonant
frequency should be approximately 25 MHz. Figure 48 shows
the recommended circuit configuration.
XTAL_SEL
PLL_LOOP_FILTER
2
90
REF_CLK
REF_CLK
95
DRV0
CFR3
XTAL
39pF
<29:28>
2
91
PLL ENABLE
94
REFCLK_OUT
CFR3
<8>
39pF
REFCLK
INPUT
SELECT
LOGIC
Figure 48. Crystal Connection Diagram
ENABLE PLL_LOOP_FILTER
1
0
1
0
IN
OUT
PLL
DIRECT DRIVEN REF_CLK
CHARGE
VCO
SYSCLK
90
91
REF_CLK
REF_CLK
PUMP DIVIDE
SELECT
3
REF_CLK
When driving the REF_CLK/
signal source, either single-ended or differential signals can be
REF_CLK
inputs directly from a
2
7
I
N
CFR3
<7:1>
VCO SEL
CFR3
<26:24>
CP
used. With a differential signal source, the REF_CLK/
CFR3
<21:19>
1
0
pins are driven with complementary signals and ac-coupled
with 0.1 µF capacitors. With a single-ended signal source, either a
single-ended-to-differential conversion can be employed or the
REF_CLK input can be driven single-ended directly. In either case,
0.1 µF capacitors are used to ac couple both REF_CLK/
pins to avoid disturbing the internal dc bias voltage of ~1.35 V.
See Figure 49 for more details.
÷2
REFCLK INPUT REFCLK INPUT
DIVIDER RESETB DIVIDER BYPASS
CFR3<14> CFR3<15>
REF_CLK
Figure 47. REF_CLK Block Diagram
The PLL enable bit is used to choose between the PLL path or
the direct input path. When the direct input path is selected, the
REF_CLK
The REF_CLK/
input resistance is ~2.5 kΩ differential
REF_CLK
REF_CLK/
pins must be driven by an external signal
(~1.2 kΩ single-ended). Most signal sources have relatively low
REF_CLK
source. Input frequencies up to 2 GHz are supported. For input
frequencies greater than 1 GHz, the input divider must be
enabled for proper operation of the device.
output impedances. The REF_CLK/
input resistance is
relatively high; therefore, its effect on the termination impedance
is negligible and can usually be chosen to be the same as the output
impedance of the signal source. The bottom two examples in
Figure 49 assume a signal source with a 50 Ω output impedance.
When the PLL is enabled, a buffered clock signal is available at
the REFCLK_OUT pin. This clock signal is the same frequency
as the REF_CLK input. This is especially useful when a crystal
is connected, because it gives the user a replica of the crystal
clock for driving other external devices. The REFCLK_OUT
buffer is controlled by two bits as listed in Table 6.
Rev. C | Page 34 of 64
Data Sheet
AD9957
0.1µF
Figure 51 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for an individual device selected from the population. Figure 51
shows that the VCO frequency ranges for a single device always
overlap when operated over the full range of conditions.
90 REF_CLK
PECL,
LVPECL,
OR
DIFFERENTIAL SOURCE,
DIFFERENTIAL INPUT.
TERMINATION
0.1µF
LVDS
DRIVER
91
REF_CLK
In conclusion, if a user wants to retain a single default value for
CFR3<26:24>, a frequency that falls into one of the ranges
found in Figure 50 should be selected. Additionally, for any
given individual device, the VCO frequency ranges overlap,
meaning that any given device exhibits no gaps in its frequency
coverage across VCO ranges over the full range of conditions.
0.1µF
BALUN
(1:1)
90
REF_CLK
SINGLE-ENDED SOURCE,
DIFFERENTIAL INPUT.
50Ω
91
REF_CLK
0.1µF
0.1µF
0.1µF
FLOW = 920
VCO5
90
REF_CLK
FHIGH = 1030
SINGLE-ENDED SOURCE,
SINGLE-ENDED INPUT.
50Ω
FLOW = 760
FHIGH = 875
VCO4
VCO3
VCO2
VCO1
VCO0
91
REF_CLK
FLOW = 650
FHIGH = 790
Figure 49. Direct Connection Diagram
FLOW = 530
FHIGH = 615
PHASE-LOCKED LOOP (PLL) MULTIPLIER
FLOW = 455
FHIGH = 530
An internal phase-locked loop (PLL) provides users of the
AD9957 the option to use a reference clock frequency that is
significantly lower than the system clock frequency. The PLL
supports a wide range of programmable frequency multiplica-
tion factors (12× to 127×) as well as a programmable charge
pump current and external loop filter components (connected
via the PLL_LOOP_FILTER pin). These features add an extra
layer of flexibility to the PLL, allowing optimization of phase
noise performance and flexibility in frequency plan develop-
ment. The PLL is also equipped with a PLL_LOCK pin.
FLOW = 400
FHIGH = 460
395
495
595
695
795
895
995
(MHz)
Figure 50. VCO Ranges Including Atypical Wafer Process Skew
FLOW = 810
FHIGH = 1180
VCO5
FLOW = 646
FHIGH = 966
VCO4
VCO3
VCO2
VCO1
VCO0
FLOW = 574
FHIGH = 904
The PLL output frequency range (fSYSCLK) is constrained to the
range of 420 MHz ≤ fSYSCLK ≤ 1 GHz by the internal VCO. In
addition, the user must program the VCO to one of six operating
ranges such that fSYSCLK falls within the specified range. Figure 50
and Figure 51 summarize these VCO ranges.
FLOW = 469
FHIGH = 709
FLOW = 402
FHIGH = 602
Figure 50 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for all devices from the available population. The implication is
that multiple devices chosen at random from the population and
operated under widely varying conditions may require different
values to be programmed into CFR3<26:24> to operate at the
same frequency. For example, Part A chosen randomly from the
population, operating in an ambient temperature of −10°C with
a system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 100b. Whereas Part B chosen randomly from the
population, operating in an ambient temperature of 90°C with a
system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 101b. If a frequency plan is chosen such that the
system clock frequency operates within one set of boundaries
(as shown in Figure 51), the required value in CFR3<26:24> is
consistent from part to part.
FLOW = 342
FHIGH = 522
335
435
535
635
735
835
935 1035 1135
(MHz)
Figure 51. Typical VCO Ranges
Table 7. VCO Range Bit Settings
VCO SEL Bits
(CFR3<26:24>)
VCO Range
000
001
010
011
100
101
110
111
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
PLL Bypassed
PLL Bypassed
Rev. C | Page 35 of 64
AD9957
Data Sheet
PLL CHARGE PUMP
In the prevailing literature, this configuration yields a third-
order, Type II PLL. To calculate the loop filter component
values, begin with the feedback divider value (N), the gain of
the phase detector (KD), and the gain of the VCO (KV) based on
the programmed VCO SEL bit settings (see Table 1 for KV). The
loop filter component values depend on the desired open-loop
bandwidth (fOL) and phase margin (φ), as follows:
The charge pump current (ICP) is programmable to provide the
user with additional flexibility to optimize the PLL performance.
Table 8 lists the bit settings vs. the nominal charge pump
current.
Table 8. PLL Charge Pump Current
ICP (CFR3<21:19>)
Charge Pump Current, ICP (μA)
πNfOL
KD KV
1
R1 =
C1 =
1+
(7)
(8)
000
001
010
011
100
101
110
111
212
237
262
287
312
337
363
387
sin( )
φ
KD KV tan(φ)
2
2N
(
πfOL
)
KD KV
N(2πfOL
1−sin
( )
φ
2
C2 =
(9)
)
cos
( )
φ
where:
KD equals the programmed value of ICP.
KV is taken from Table 1.
EXTERNAL PLL LOOP FILTER COMPONENTS
The PLL_LOOP_FILTER pin provides a connection interface to
attach the external loop filter components. The ability to use
custom loop filter components gives the user more flexibility to
optimize the PLL performance. The PLL and external loop filter
components are shown in Figure 52.
Ensure that proper units are used for the variables in Equation 7
through Equation 9. ICP must be in amps, not μA as appears in
Table 8; KV must be in Hz/V, not MHz/V as listed in Table 1; the
loop bandwidth (fOL) must be in Hz; the phase margin (φ) must
be in radians.
AVDD
For example, suppose the PLL is programmed such that
ICP = 287 μA, KV = 625 MHz/V, and N = 25. If the desired loop
bandwidth and phase margin are 50 kHz and 45°, respectively,
the loop filter component values are R1 = 52.85 Ω, C1 = 145.4 nF,
and C2 = 30.11 nF.
C1
C2
R1
PLL_LOOP_FILTER
2
PLL LOCK INDICATION
REFCLK PLL
PLL IN
When the PLL is in use, the PLL_LOCK pin provides an active
high indication that the PLL has locked to the REFCLK input
signal. When the PLL is bypassed, the PLL_LOCK pin defaults
to Logic 0.
PFD
CP
VCO
PLL OUT
÷N
Figure 52. REFCLK PLL External Loop Filter
Rev. C | Page 36 of 64
Data Sheet
AD9957
ADDITIONAL FEATURES
OUTPUT SHIFT KEYING (OSK)
•
•
•
The maximum amplitude scale factor
The amplitude step size
The time interval between steps
The OSK function (Figure 53) is only available in single tone
mode. It allows the user to control the output signal amplitude
of the DDS. Both manual and automatic modes are available.
The amplitude ramp parameters reside in the 32-bit ASF
register and are programmed via the serial I/O port. The
amplitude step interval is set using the 16-bit amplitude ramp
rate portion of the ASF register (Bits<31:16>). The maximum
amplitude scale factor is set using the 14-bit amplitude scale
factor in the ASF register (Bits<15:2>). The amplitude step size
is set using the 2-bit amplitude step size portion of the ASF
register (Bits<1:0>). The direction of the ramp (positive or
negative slope) is controlled by the external OSK pin. When
the OSK pin is a Logic 1, the slope is positive; otherwise, it is
negative.
OSK
60
OSK ENABLE
AUTO OSK ENABLE
MANUAL OSK EXTERNAL
LOAD ARR AT I/O_UPDATE
TO DDS
14
OSK
CONTROLLER
AMPLITUDE
CONTROL
PARAMETER
16
14
2
AMPLITUDE RAMP RATE
(ASF<31:16>)
AMPLITUDE SCALE FACTOR
(ASF<15:2>)
AMPLITUDE STEP SIZE
(ASF<1:0>)
The step interval is controlled by a 16-bit programmable timer
that is clocked at a rate of ¼ fSYSCLK. The timer period sets the
interval between amplitude steps. The step time interval (Δt)
is given by
DDS CLOCK
Figure 53. OSK Block Diagram
4M
fSYSCLK
∆t =
The operation of the OSK function is governed by four control
register bits, the external OSK pin, and the entire 32 bits of the
ASF register. The primary control for the OSK block is the OSK
enable bit. When this bit is set, the OSK function is enabled;
otherwise, the OSK function is disabled. When disabled, the
other OSK input controls are ignored and the internal clocks are
shut down to conserve power.
where M is the 16-bit number stored in the amplitude ramp rate
portion of the ASF register. For example, if fSYSCLK = 750 MHz
and M = 23,218 (0x5AB2), then Δt ≈ 123.8293 μs.
The output of the OSK function is a 14-bit unsigned data bus
that controls the amplitude of the DDS output (as long as the
OSK enable bit is Logic 1). When the OSK pin is Logic 1, the
OSK output value starts at 0 and increments by the programmed
amplitude step size until it reaches the programmed maximum
amplitude value. When the OSK pin is Logic 0, the OSK output
starts at its present value and decrements by the programmed
amplitude step size until it reaches 0.
When the OSK function is enabled, automatic and manual
operation is selected via the Select Auto-OSK bit. When this bit
is set, the automatic mode is active; otherwise, the manual
mode is active.
Manual OSK
In manual mode, output amplitude is varied by successive write
operations to the amplitude scale factor portion of the ASF
register. The rate at which amplitude changes can be applied to
the output signal is limited by the speed of the serial I/O port.
In manual mode, the OSK pin functionality depends on the
state of the manual OSK external control bit. It is either inoperative
or used to switch the output amplitude between the programmed
amplitude scale factor value and zero. When operational, a Logic 0
on the OSK pin forces the output amplitude to zero whereas a
Logic 1 on the OSK pin causes the output amplitude to be scaled
by the amplitude scale factor value.
The OSK output does not necessarily attain the maximum
amplitude—the OSK pin may switch to Logic 0 before attaining
the maximum value.
The OSK output does not necessarily reach a value of zero—the
OSK pin may switch to Logic 1 before attaining the zero value.
The OSK output is initialized to 0 at power-up. It is also set to 0
when the OSK enable bit is Logic 0 or when the OSK enable bit
is Logic 1, but the Select Auto-OSK bit is Logic 0.
The amplitude step size of the OSK output is set by the ampli-
tude step size bits in the ASF register according to the values
listed in Table 9. The step size refers to the LSB weight of the
14-bit OSK output.
Automatic OSK
In automatic mode, the OSK function automatically generates
a linear amplitude vs. time profile (or amplitude ramp). The
amplitude ramp is controlled via three parameters, as follows:
The OSK output cannot exceed the maximum amplitude value
programmed into the ASF register.
Rev. C | Page 37 of 64
AD9957
Data Sheet
Table 9. OSK Amplitude Step Size
I/O_UPDATE PIN
ASF<1:0>
Amplitude Step Size
By default, the I/O_UPDATE pin is an input that serves as a
strobe signal to allow synchronous update of the device operating
parameters. For example, frequency, phase, and amplitude con-
trol words for the DDS can be programmed using the serial I/O
port. However, the serial I/O port is an asynchronous interface;
consequently, programming of the device operating parameters
using the I/O port is not synchronized with the internal timing.
Using the pin, I/O_UPDATE, the user can synchronize the
application of certain programmed operating parameters with
external circuitry when new parameters are programmed into
the I/O registers. A rising edge on I/O_UPDATE initiates transfer
of the register contents to the internal workings of the device.
00
01
10
11
1
2
4
8
As mentioned earlier, the step interval is controlled by a 16-bit
programmable timer. Normally, this timer is loaded with the
programmed timing value whenever the timer expires, thus
initiating a new timing cycle. However, three events cause the
timer to have its timing value reloaded prior to the timer expiring.
One such event is when the Select Auto-OSK bit is transitioned
from a Logic 0 state to a Logic 1 state followed by an I/O update. A
second such event is a change of state in the OSK pin. The third
event is dependent on the status of the Load ARR @ I/O Update
bit. If this bit is Logic 0, no action occurs; otherwise, when the
I/O_UPDATE pin is asserted (or a profile change occurs), the
timer resets to its initial starting point.
The transfer of programmed data from the programming
registers to the internal hardware is also accomplished by
changing the state of the profile pins.
AUTOMATIC I/O UPDATE
The AD9957 offers an option whereby the I/O update function
is asserted automatically rather than relying on an external
signal supplied by the user. This feature is enabled by setting the
Internal I/O Update Active bit in CFR2.
PROFILES
Each of the three operating modes of the AD9957 support the
use of profiles, which consist of a group of registers containing
pertinent operating parameters for a particular operating mode.
Profiles enable rapid switching between parameter sets. Profile
parameters are programmed via the serial I/O port. Once pro-
grammed, a specific profile is activated by means of three
external pins (PROFILE<2:0>). A particular profile is activated
by providing the appropriate logic levels to the profile control
pins per the settings listed in Table 10.
When this feature is active, the I/O_UPDATE pin becomes an
output pin. It generates an active high pulse each time an inter-
nal I/O update occurs. The duration of the pulse is approximately
12 cycles of SYSCLK. This I/O update strobe can be used to
notify an external controller that the device has generated an
I/O update internally.
The repetition rate of the internal I/O update is programmed
via the serial I/O port. Two parameters control the repetition
rate. The first parameter consists of the two I/O update rate
control bits in CFR2. The second parameter is the 32-bit word
in the I/O update rate register that sets the range of an internal
counter.
Table 10. Profile Control Pins
PROFILE<2:0>
Active Profile
000
001
010
011
100
101
110
111
0
1
2
3
4
5
6
7
The I/O update rate control bits establish a divide by 1, 2, 4, or 8
of a clock signal that runs at ¼ fSYSCLK. The output of the divider
clocks the aforementioned 32-bit internal counter. The repetition
rate of the I/O update is given by
fSYSCLK
fI /O _UPDATE
Consider an application of basic two-tone frequency shift
keying (FSK) where binary data is transmitted by selecting
between two different frequencies: a mark frequency (Logic 1)
and a space frequency (Logic 0). To accommodate FSK, the
Profile 0 register is programmed with the appropriate frequency
tuning word for a space, and the Profile 1 register is programmed
with the appropriate frequency tuning word for a mark. Then,
with the PROFILE1 and PROFILE2 pins tied to Logic 0, the
PROFILE0 pin is used to transmit the data bits. The logic state
of the PROFILE0 pin causes the appropriate mark and space
frequencies to be generated.
2A B
where:
A is the value of the 2-bit word comprising the I/O update rate
control bits.
B is the value of the 32-bit word stored in the I/O update rate
register.
If B is programmed to 0x0003 or less, the I/O_UPDATE pin no
longer pulses, but assumes a static Logic 1 state.
Rev. C | Page 38 of 64
Data Sheet
AD9957
POWER-DOWN CONTROL
Each of these 16 pins is assigned a unique bit in both the 16-bit
GPIO configuration register and the 16-bit GPIO data register.
The status of each bit in the GPIO configuration register assigns
the associated pin as either a GPIO input or output (0 = input,
1 = output) based on the data listed in Table 11.
The AD9957 offers the ability to independently power down four
specific sections of the device. Power-down functionality applies
to the digital core, DAC, auxiliary DAC, and REFCLK input.
A power-down of the digital core disables the ability to update
the serial I/O port. However, the digital power-down bit can
still be cleared via the serial port to prevent the possibility of a
nonrecoverable state.
When a GPIO pin is programmed as an output, the logic state
written to the associated bit of the GPIO data register (via the
serial I/O port) appears at the GPIO pin. When a GPIO pin is
programmed as an input, the logic state of the GPIO pin can be
read (via the serial I/O port) in the associated bit position in the
GPIO data register. Note that the GPIO data register does not
require an I/O update.
Software power-down is controlled through four independent
power-down bits in CFR1. Software control requires forcing the
EXT_PWR_DWN pin to a Logic 0 state. In this case, setting the
desired power-down bits (via the serial I/O port) powers down
the associated functional block; clearing the bits restores the
function.
Table 11. GPIO Pins vs. Configuration and Data Register Bits
Pin Label
D17
D16
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D3
D2
D1
Configuration Bit
Data Bit
Alternatively, all four functions can be simultaneously powered
down via external hardware control through the EXT_PWR_DWN
pin. Forcing this pin to Logic 1 powers down all four circuit
blocks, regardless of the state of the power-down bits. That is,
the independent power-down bits in CFR1 are ignored and
overridden when EXT_PWR_DWN is Logic 1.
15
14
13
12
11
10
9
8
7
6
5
15
14
13
12
11
10
9
8
7
6
5
Based on the state of the external power-down control bit, the
EXT_PWR_DWN pin produces either a full power-down or a
fast recovery power-down. The fast recovery power-down mode
maintains power to the DAC bias circuitry and the PLL, VCO,
and input section of the REFCLK circuitry. Although the fast
recovery power-down does not conserve as much power as the
full power-down, it allows the device to very quickly awaken
from the power-down state.
4
3
2
1
4
3
2
1
GENERAL-PURPOSE I/O (GPIO) PORT
D0
0
0
The GPIO function is only available when the AD9957 is pro-
grammed for QDUC mode and the Blackfin interface mode is
active. Because the Blackfin serial interface uses only two of
the 18 parallel data port pins (D<5:4>), the remaining 16 pins
(D<17:6> and D<3:0>) are available as a GPIO port.
Rev. C | Page 39 of 64
AD9957
Data Sheet
SYNCHRONIZATION OF MULTIPLE DEVICES
The synchronization mechanism relies on the premise that the
REFCLK signal appearing at each device is edge aligned with all
others resulting from the external REFCLK distribution system
(see Figure 59).
OVERVIEW
The internal clocks of the AD9957 provide the timing for the
propagation of data along the baseband signal processing path.
These internal clocks are derived from the internal system clock
(SYSCLK) and are all submultiples of the SYSCLK frequency.
The logic state of all of these clocks in aggregate during any
given SYSCLK cycle defines a unique clock state. The clock state
advances with each cycle of SYSCLK, but the sequence of clock
states is periodic. By definition, multiple devices are synchro-
nized when their clock states match and they transition between
states simultaneously. Clock synchronization allows the user to
asynchronously program multiple devices, but synchronously
activate the programming by applying a coincident I/O update
to all devices. It also allows multiple devices to operate in unison
when the parallel port is in use with either the QDUC or inter-
polating DAC mode (see Figure 59) or when the dual serial port
(BlackFin interface) is in use.
CLOCK GENERATOR
The clock generator provides the necessary timing for the inter-
nal workings of the AD9957. The goal of the synchronization
mechanism is to force the clock generator to a known state
coincident with an external synchronization signal. The clock
generator consists of three separate clock trees (see Figure 55).
The first is a common clock generator that is active for all
programmed modes of operation (single tone, QDUC, or
interpolating DAC). The common clock generates the
SYNC_CLK signal that appears at Pin 55. The second clock
generator is active when the device is programmed for the
interpolating DAC mode or quadrature modulation mode using
the parallel data port. It uses the SYSCLK/2 output of the common
clock as its primary timing source. The third clock generator is
active when the device is programmed for quadrature modulation
mode using the BlackFin interface.
The function of the synchronization logic in the AD9957 is to
force the internal clock generator to a predefined state coincident
with an external synchronization signal applied to the SYNC_IN
pins. Forcing multiple devices to the same clock state coincident
with the same external signal is, by definition, synchronization.
Figure 54 is a block diagram of the synchronization function.
The synchronization logic consists of two independent blocks, a
sync generator and a sync receiver, both of which use the local
SYSCLK signal for internal timing.
COMMON CLOCK
GENERATOR
SYNC
PULSE
÷2
÷2
SYSCLK
SYNC_CLK
CLOCK GENERATOR FOR INTERPOLATING
DAC MODE OR QUADRATURE MODULATION
MODE WITH THE PARALLEL DATA PORT
REF_CLK
INPUT
CIRCUITRY
90
91
÷R
÷2
PDCLK
SYSCLK
REF_CLK
6
CLOCK GENERATOR FOR
QUADRATURE MODULATION MODE
WITH THE BLACKFIN INTERFACE
5
÷R
÷2
÷2
÷2
÷2
9
SYNC
GENERATOR
SYNC_OUT
10
6
SYNC STATE
PRESET VALUE
SYNC
RECEIVER
DELAY
SYNC
RECEIVER
ENABLE
Figure 55. Clock Generator
5
SYNC GENERATOR
The sync generator block is shown in Figure 56. It is activated
via the Sync Generator Enable bit. It allows for one AD9957 in a
group to function as a master timing source with the remaining
devices slaved to the master.
7
8
INPUT DELAY
SYNC_IN
AND EDGE
DETECTION
SYNC
INTERNAL
CLOCKS
RECEIVER
12
SETUP AND
HOLD VALIDATION
SYNC_SMP_ERR
6
4
SYNC STATE
SYNC
SYNC
TIMING
VALIDATION
DISABLE
PRESET VALUE VALIDATION
DELAY
Figure 54. Synchronization Circuit Block Diagram
Rev. C | Page 40 of 64
Data Sheet
AD9957
SYNC RECEIVER
9
PROGAMMABLE
DELAY
D
Q
SYNC_OUT
SYSCLK
÷16
÷2R
10
The sync receiver block (shown in Figure 57) is activated via the
Sync Receiver Enable bit. The sync receiver consists of three
subsections: the input delay and edge detection block, the
internal clock generator block, and the setup-and-hold valida-
tion block.
LVDS
DRIVER
5
0
1
R
SYNC
GENERATOR
DELAY
SYNC
POLARITY
SYNC
GENERATOR
ENABLE
The clock generator block remains operational even when the
sync receiver is not enabled.
Figure 56. Sync Generator
The sync receiver accepts an LVDS-compatible signal at the
SYNC_IN pins. Typically, the signal applied to the SYNC_IN
pins originates from the SYNC_OUT of another AD9957
functioning as a master timing unit. The sync receiver expects a
periodic synchronization pulse that meets certain frequency
requirements based on the operating mode of the AD9957.
When programmed for single tone mode, the frequency of
SYNC_IN must satisfy
The sync generator produces an LVDS-compatible clock signal
with a 50% duty cycle that appears at the SYNC_OUT pins. The
frequency of the SYNC_OUT signal can be one of two possible
rates. With the AD9957 programmed for any of the following
modes:
•
•
Single tone mode
Quadrature modulation mode with the CCI filter bypassed
(that is, interpolation factor is 1)
fSYSCLK
fSYNC _ IN
=
•
Interpolating DAC mode with the CCI filter bypassed (that
is, interpolation factor is 1)
4M
where M is any integer greater than zero. When programmed
for quadrature modulation mode (using the parallel data port)
or interpolating DAC mode, the frequency of SYNC_IN must
satisfy
The frequency of SYNC_OUT is given by:
fSYSCLK
fSYNC _ OUT
=
16
fSYSCLK
16(R + M)
With the AD9957 programmed for the QDUC or interpolating
DAC mode and with the CCI filter not bypassed (that is, R>1)
the frequency of SYNC_OUT is given by
fSYNC _ IN
=
where R is the programmed CCI interpolation factor and M is
any integer greater than or equal to zero. When programmed
for quadrature modulation mode using the BlackFin interface,
the frequency of SYNC_IN must satisfy
fSYSCLK
32R
fSYNC _ OUT
=
where R is the programmed interpolation factor of the CCI filter.
fSYSCLK
32(R + M)
fSYNC _ IN
=
The signal at the SYNC_OUT pins is edge aligned with either
the rising or falling edge of the internal SYSCLK signal as deter-
mined by the Sync Polarity bit. Because the SYNC_OUT signal is
synchronized with the internal SYSCLK of the master device, the
master device SYSCLK serves as the reference timing source for
all slave devices.
where R is the programmed CCI interpolation factor and M is
any integer greater than or equal to zero.
The user can adjust the output delay of the SYNC_OUT signal
in steps of ~75 ps by programming the 5-bit sync generator
delay word via the serial I/O port. The programmable output
delay facilitates added edge timing flexibility to the overall
synchronization mechanism.
Rev. C | Page 41 of 64
AD9957
Data Sheet
CLOCK
STATE
SYNC STATE
PRESET VALUE
SYNC
RECEIVER
ENABLE
DELAYED SYNC-IN SIGNAL
6
SYNC
RECEIVER
DELAY
P
R
E
S
E
T
Q
.0 .
. .
. .
INTERNAL
CLOCKS
LVDS
5
RECEIVER
RISING EDGE
DETECTOR
AND
Q
N
SYNC_IN+
SYNC_IN–
7
8
PROGAMMABLE
DELAY
LOAD
STROBE
GENERATOR
CLOCK
GENERATOR
SETUP AND HOLD
VALIDATION
12
SYNC_SMP_ERR
SYSCLK
4
SYNC
SYNC
VALIDATION
DELAY
SYNC PULSE
TIMING
VALIDATION
DISABLE
Figure 57. Sync Receiver
to each device in a group. This flexibility is limited, however,
because the sync state preset value must adhere to certain
bounds to satisfy internal timing requirements. Regardless of
the programmed sync state preset value, the preset value is
internally constrained to the range, 2 to R, where R is the CCI
filter interpolation factor. A programmed value of 0 or 1 is forced
to 2, whereas a programmed value greater than R is forced to R.
When a device other than another AD9957 provides the
SYNC_IN signal it must be LVDS compatible. Furthermore,
although SYNC_IN is typically considered to be a periodic
clock signal, it is not an absolute requirement. It is feasible to
drive the SYNC_IN pins with a single synchronization pulse as
long as its edge transition meets the setup/hold timing required
for the internally generated sync pulse (as detailed later in this
section). However, using a periodic SYNC_IN signal has the
distinct advantage that should any of the devices arbitrarily lose
synchronization it automatically resynchronizes with the arrival
of the next SYNC_IN edge.
SETUP/HOLD VALIDATION
Synchronization of the AD9957 internal clock generator with
other external devices relies on the ability of the sync receiver’s
edge detection circuit to generate a valid sync pulse. This
requires proper sampling of the rising edge of the delayed
SYNC_IN signal with the rising edge of the local SYSCLK. If the
edge timing of these signals fails to meet the setup or hold time
requirements of the internal latches in the edge detection
circuitry, the proper generation of a sync pulse is in jeopardy.
The setup-and-hold validation block (see Figure 58) gives the
user a means to validate that proper edge timing exists between
the two signals. The Sync Timing Validation Disable bit in
Control Function Register 2 controls whether or not the setup-
and-hold validation block is active.
The 5-bit sync receiver delay word in the multichip sync register
delays the SYNC_IN signal in steps of ~75 ps. This provides the
ability to time align the arrival of the SYNC_IN signal to
multiple devices by compensating for unequal propagation times.
The edge detection logic in the sync receiver generates a
synchronization pulse (sync pulse) having a duration of one
SYSCLK cycle with a repetition rate equal to that of the signal
applied to the SYNC_IN pins. To produce the sync pulse, the
strobe generator samples the delayed rising edge of the SYNC_IN
signal with the rising edge of the local SYSCLK. The generation
of this sync pulse is crucial to the operation of the synchroniza-
tion mechanism, because it performs the task of placing the
clock generator into a known state. The sync pulse presets the
R-divider stage of the internal clock generator, which behaves as
a presettable downcounter (see Figure 55). The programmable
6-bit sync state preset value word in the multichip sync register
establishes the preset state. The preset state is only active for a
single SYSCLK period, after which the clock generator is free to
cycle through its state sequence until the next sync pulse arrives
(see Figure 55). In addition to presetting the R-divider, the sync
pulse also synchronously presets the other dividers to a proper
state in order to preserve the cadence of the clock tree.
The validation block makes use of a specified time window
(programmable in increments of ~75 ps via the 4-bit sync
validation delay word in the multichip sync register). The setup
validation and hold validation circuits use latches identical to
those in both the rising edge detector and strobe generator. The
programmable time window skews the timing between the local
SYSCLK signal and the delayed sync-in signal. If the hold valida-
tion and setup validation circuits fail to produce the same logic
states, it is an indication of a possible setup or hold violation.
The check logic of Figure 58 monitors the state of the setup and
hold validation latches. If they are not equal (that is, a potential
setup/hold violation exists), a Logic 1 is stored in an internal
validation result latch; otherwise, a Logic 0 is stored. The state
of validation result latch appears at the SYNC_SMP_ERR pin.
The ability to program the clock state preset value provides the
flexibility to synchronize devices, but with specific relative clock
state offsets by assigning a different sync state preset value word
Rev. C | Page 42 of 64
Data Sheet
AD9957
The validation result latch is in a reset state whenever the sync
receiver is disabled, which forces the SYNC_SMP_ERR pin to a
Logic 0 state. To reset the validation result latch when the sync
receiver is active, however, requires the use of the Sync Timing
Validation Disable bit in the multichip sync register. To make a
setup/hold validation measurement is a two-step process. First,
write a Logic 1 to the sync timing validation disable bit. Then,
to make a measurement, write a Logic 0. The first action resets
the validation result latch and holds it in a reset state; the
second action releases the reset state and enables the validation
result latch to capture a setup/hold validation measurement.
Each time a new setup/hold validation check is desired, this
two-step procedure must be performed.
Because the programmed value of the sync validation delay
establishes the time window for a setup/hold measurement,
the amount of delay is an important consideration for proper
operation of the validation block. The value chosen should
represent a small fraction of the SYSCLK period. For example,
if the SYSCLK frequency is 1 GHz (1000 ps period), then a
reasonable sync validation delay value is 4 (~300 ps). This
allows the validation block to ensure that the local SYSCLK
and the delayed SYNC_IN edges exhibit at least 300 ps of
timing separation. Choosing too large a value can cause the
validation block to indicate a setup/hold violation when one
does not exist. Choosing too small a value can cause the
validation block to miss a setup/hold violation when one
actually exists.
SYNC RECEIVER
RISING EDGE
DETECTOR
AND STROBE
GENERATOR
FROM
SYNC
RECEIVER
DELAY
TO
CLOCK
LOGIC
GENERATION
LOGIC
SYNC
PULSE
D
Q
SETUP AND HOLD VALIDATION
SETUP
VALIDATION
DELAY
D Q
4
4
12
SYNC_SMP_ERR
4
SYNC VALIDATION
DELAY
D Q
SYSCLK
DELAY
HOLD
VALIDATION
SYNC TIMING VALIDATION DISABLE
Figure 58. Sync Timing Validation Block
Rev. C | Page 43 of 64
AD9957
Data Sheet
generator is coordinated with the others. This is the role of the
synchronization and delay equalization block. This block accepts
the SYNC_OUT signal generated by the master device and
redistributes it to the SYNC_IN input of the slave units (as well
as feeding it back to the master). The goal of the redistributed
SYNC_OUT signal from the master device is to deliver an edge-
aligned SYNC_IN signal to all of the sync receivers.
SYNCHRONIZATION EXAMPLE
To accomplish the synchronization of multiple devices provide
each AD9957 with a SYNC_IN signal that is edge aligned across
all the devices. If the SYNC_IN signal is edge aligned at all devices,
and all devices have the same sync receiver delay and sync state
preset value, then they all have matching clock states (that is,
they are synchronized). Figure 59 shows this concept with three
AD9957s in synchronization. One device operates as a master
timing unit with the others synchronized to the master.
Assuming that all devices share the same REFCLK edge timing
(due to the clock distribution and delay equalization block) and
that all devices share the same SYNC_IN edge timing (due to
the synchronization and delay equalization block), then all
devices should be generating an internal sync pulse in unison
(assuming all have the same value for the sync receiver delay).
With the further stipulation that all devices have the same sync
state preset value, then the synchronized sync pulses cause all of
the devices to assume the same predefined clock state simultane-
ously. That is, all devices have their internal clocks fully
synchronized.
The master device must have its SYNC_IN pins included as part
of the synchronization distribution and delay equalization mecha-
nism. This ensures that the master maintains synchronous timing
with the other units.
The synchronization mechanism begins with the clock distribu-
tion and delay equalization block, which ensures that all devices
receive an edge-aligned REFCLK signal. However, even though
the REFCLK signal is edge aligned among all devices, this alone
does not guarantee that the clock state of each internal clock
CLOCK DISTRIBUTION
AND
DELAY EQUALIZATION
CLOCK
SOURCE
EDGE
ALIGNED
(FOR EXAMPLE, AD951x)
AT REF_CLK
INPUTS
REF_CLK
DATA
AD9957
FPGA
MASTER DEVICE
NUMBER 1
SYNC SYNC
IN
OUT
EDGE
ALIGNED
AT SYNC_IN
INPUTS.
REF_CLK
DATA
AD9957
FPGA
NUMBER 2
SYNC SYNC
IN
OUT
SYNCHRONIZATION
DISTRIBUTION AND
DELAY EQUALIZATION
(FOR EXAMPLE AD951x)
REF_CLK
DATA
AD9957
FPGA
NUMBER 3
SYNC SYNC
IN
OUT
Figure 59. Multichip Synchronization Example
Rev. C | Page 44 of 64
Data Sheet
AD9957
signal process path by updating a parallel register at the proper
time. The data is transferred from the parallel register to the
signal processing chain and all timing has been verified regard-
less of the phase relationship between the updating of the parallel
register and the signal processing clock.
I/Q PATH LATENCY
The I/Q latency through the AD9957 is easiest to describe in
terms of system clock (SYSCLK) cycles and is a function of the
AD9957 configuration (that is, which mode and which optional
features are engaged). The I/Q latency is primarily affected by
the programmable CCI rate.
Example
Quadrature modulation mode = 18-bit parallel data
Reference clock multiplier = bypassed
Input scale multiplier = off
Inverse CCI = off
The values in Table 12 should be considered estimates because
observed latency may be data dependent. The latency was
calculated using the linear delay model for FIR filters. N = CCI
rate (programmable interpolation rate, 2 to 63, 1 if bypassed).
CCI rate = 20
Inverse SINC = on
Output scale = off
In BFI mode, the latency through the AD9957 may not be con-
stant for multiple transmissions. This is due to the relationship
between the phase of the clock that drives the first half-band
filter and the frame sync signal coming from the Blackfin,
which is unknown and denoted as x in Table 12. The design
successfully transfers data from the data assembler logic to the
Latency = (16 × 20) + (4 × 20) + (4 × 20) + (69 × 20) +
(4 × 20 + 8) + 22 + 8 + 2 + 8 = 1988 SYSCLKs
Table 12.
Stage
Quadrature Modulation Mode—Parallel Quadrature Modulation Mode—BFI Interpolation DAC Mode
Input Demuxplexer
16N
(16 + x)N
28N
where x = 0 to 15
Not available in BFI mode
Input Scale Multiplier
Inverse CCI Filter
Active: 8N
Bypassed: 4N
Active: 8N
Bypassed: 4N
69N
Active: 4N + 8
Bypass: 2N + 4
22
Active: 8N
Bypassed: 4N
Active: 8N
Bypassed: 4N
69N
Active: 4N + 8
Bypass: 2N + 4
0
Active: 8N
Bypassed: 4N
345N
Active: 4N + 8
Bypass: 2N + 4
22
Half-Band Filters
CCI Filter
Modulator
Inverse Sinc Filter
Active: 8
Bypass: 2
Active: 8
Bypass: 2
Active: 12
Bypass: 2
8
Active: 8
Bypass: 2
Active: 12
Bypass: 2
8
Output Scale Multiplier Active: 12
Bypass: 2
DAC Interface
8
Rev. C | Page 45 of 64
AD9957
Data Sheet
POWER SUPPLY PARTITIONING
The AD9957 features multiple power supplies, and their power
consumption varies with its configuration. This section covers
which power supplies can be grouped together and how the
power consumption of each block varies with frequency.
1.8 V SUPPLIES
DVDD (Pin 17, Pin 23, Pin 30, Pin 47, Pin 57, Pin 64)
These pins can be grouped together. Their current consumption
increases linearly with the system clock frequency. A system
clock of 1 GHz produces a typically current consumption of
610 mA in QDUC mode. There is also a slight (~5%) increase
as fOUT increases from 50 MHz to 400 MHz.
The values quoted in this section are for comparison only. Refer
to Table 1 for exact values. With each group, bypass capacitors of
1 μF in parallel with a 10 μF capacitor should be used.
AVDD (Pin 3)
The recommendations here are for typical applications, for
which there are four groups of power supplies: 3.3 V digital,
3.3 V analog, 1.8 V digital, and 1.8 V analog.
This 1.8 V supply powers the REFCLK multiplier (PLL) and
consumes about 7 mA. For applications demanding the highest
performance with the PLL enabled, this supply should be
isolated from other 1.8 V AVDD supplies with a separate
regulator. For less demanding applications this supply can be
run off the same regulator as Pin 89, Pin 92 with a ferrite bead
to isolate Pin 3 from Pin 89, and Pin 89.
Applications demanding the highest performance may require
additional power supply isolation.
3.3 V SUPPLIES
DVDD_I/O (Pin 11, Pin 15, Pin 21, Pin 28, Pin 45, Pin 56,
Pin 66)
The loop filter for the PLL should directly connect to Pin 3. If
the PLL is bypassed, pin 3 should still be powered, but isolation
is not critical.
These 3.3 V supplies can be grouped together. The power
consumption on these pins varies dynamically with serial port
activity.
AVDD (Pin 6)
AVDD (Pin 74 to Pin 77 and Pin 83)
This pin can be grouped together with the DVDD 1.8V supply
pins. For the highest performance, a ferrite bead should be used
for isolation, with a separate regulator being ideal.
These are 3.3 V DAC power supplies that typically consume
about 28 mA. At a minimum, a ferrite bead should be used to
isolate these from other 3.3 V supplies, with a separate regulator
being ideal. The current consumption of these supplies consist
mainly of biasing current and do not vary with frequency.
AVDD (Pin 89 and Pin 92)
This 1.8 V supply for the REFCLK input consumes about
15 mA. The supply can be run off the same as Pin 3 with a
ferrite bead to isolate Pin 3 from Pin 89 and Pin 92. At a
minimum, a ferrite bead should be used to isolate these from
other 1.8 V supplies. However, for applications demanding the
highest performance, a separate regulator is recommended.
Rev. C | Page 46 of 64
Data Sheet
AD9957
SERIAL PROGRAMMING
For a read cycle, Phase 2 is the same as the write cycle with the
following differences: Data is read from the active registers, not
the serial port buffer, and data is driven out on the falling edge
of SCLK.
CONTROL INTERFACE—SERIAL I/O
The AD9957 serial port is a flexible, synchronous serial commu-
nications port allowing easy interface to many industry-standard
microcontrollers and microprocessors.
Note that to read back any profile register (0x0E to 0x15), the
three external profile pins must be used. For example, if the
profile register is Profile 5 (0x13) then PROFILE<0:2> pins
must equal 101.This is not required to write to profile registers.
The interface allows read/write access to all registers that configure
the AD9957. MSB-first or LSB-first transfer formats are sup-
ported. In addition, the serial interface port can be configured
as a single pin input/output (SDIO) allowing a two-wire interface,
or it can be configured as two unidirectional pins for input/output
(SDIO/SDO), enabling a 3-wire interface. Two optional pins
INSTRUCTION BYTE
The instruction byte contains the following information as
shown in the instruction byte bit map.
CS
(I/O_RESET and ) enable greater flexibility for designing
systems with the AD9957.
Instruction Byte Information Bit Map
GENERAL SERIAL I/O OPERATION
MSB
D7
LSB
D0
A0
There are two phases to a serial communications cycle. The first
is the instruction phase to write the instruction byte into the
AD9957. The instruction byte contains the address of the regis-
ter to be accessed (see the Register Map and Bit Descriptions
section) and defines whether the upcoming data transfer is a
write or read operation.
D6
D5
D4
D3
D2
D1
R/W
X
X
A4
A3
A2
A1
W
R/ —Bit 7 of the instruction byte determines whether a read
or write data transfer occurs after the instruction byte write.
Logic 1 indicates a read operation. Cleared indicates a write
operation.
For a write cycle, Phase 2 represents the data transfer between
the serial port controller to the serial port buffer. The number
of bytes transferred is a function of the register being accessed.
For example, when accessing the Control Function Register 2
(Address 0x01), Phase 2 requires that four bytes be transferred.
Each bit of data is registered on each corresponding rising edge
of SCLK. The serial port controller expects that all bytes of the
register be accessed; otherwise, the serial port controller is put
out of sequence for the next communication cycle. However,
one way to write fewer bytes than required is to use the I/O_RESET
pin feature. The I/O_RESET pin function can be used to abort
an I/O operation and reset the pointer of the serial port con-
troller. After an I/O reset, the next byte is the instruction byte.
Note that every completed byte written prior to an I/O reset is
preserved in the serial port buffer. Partial bytes written are not
preserved. At the completion of any communication cycle, the
AD9957 serial port controller expects the next eight rising
SCLK edges to be the instruction byte for the next communi-
cation cycle.
X, X—Bit 6 and Bit 5 of the instruction byte are don’t cares.
A4, A3, A2, A1, A0—Bit 4, Bit 3, Bit 2, Bit 1, and Bit 0 of the
instruction byte determine which register is accessed during the
data transfer portion of the communications cycle.
SERIAL I/O PORT PIN DESCRIPTIONS
SCLK—Serial Clock
The serial clock pin is used to synchronize data to and from the
AD9957 and to run the internal state machines.
CS
—Chip Select Bar
An active low input that allows more than one device on the
same serial communications line. The SDO and SDIO pins go
to a high impedance state when this input is high. If driven high
during any communications cycle, that cycle is suspended until
CS
CS
is reactivated low. Chip select ( ) can be tied low in
systems that maintain control of SCLK.
SDIO—Serial Data Input/Output
After a write cycle, the programmed data resides in the serial
port buffer and is inactive. I/O_UPDATE transfers data from
the serial port buffer to active registers. The I/O update can
either be sent after each communication cycle or when all serial
operations are complete. In addition, a change in profile pins
can initiate an I/O update.
Data is always written into the AD9957 on this pin. However,
this pin can be used as a bidirectional data line. Bit 1 of CFR1,
Register Address 0x00, controls the configuration of this pin.
The default is cleared, which configures the SDIO pin as
bidirectional.
Rev. C | Page 47 of 64
AD9957
Data Sheet
SDO—Serial Data Out
SERIAL I/O TIMING DIAGRAMS
Data is read from this pin for protocols that use separate lines
for transmitting and receiving data. In the case where the
AD9957 operates in a single bidirectional I/O mode, this pin
does not output data and is set to a high impedance state.
Figure 60 through Figure 63 provide basic examples of the tim-
ing relationships between the various control signals of the serial
I/O port. Most of the bits in the register map are not transferred
to their internal destinations until assertion of an I/O update,
which is not included in the timing diagrams that follow.
I/O_RESET—Input/Output Reset
MSB/LSB TRANSFERS
I/O_RESET synchronizes the I/O port state machines without
affecting the addressable registers contents. An active high
input on the I/O_RESET pin causes the current communication
cycle to abort. After I/O_RESET returns low (Logic 0), another
communication cycle can begin, starting with the instruction
byte write.
The AD9957 serial port can support both most significant bit
(MSB) first or least significant bit (LSB) first data formats. This
functionality is controlled by Bit 0 in Control Function Register 1
(0x00). The default format is MSB first. If LSB first is active,
all data, including the instruction byte, must follow LSB-first
convention. Note that the highest number found in the bit range
column for each register is the MSB and the lowest number is
the LSB for that register (see the Register Map and Bit
I/O_UPDATE—Input/Output Update
The I/O_UPDATE initiates the transfer of written data from
the I/O port buffer to active registers. I/O_UPDATE is active
on the rising edge and its pulse width must be greater than one
SYNC_CLK period. It is either an input or output pin depending
on the programming of the Internal I/O Update Active bit.
Descriptions section and Table 13).
INSTRUCTION CYCLE
CS
DATA TRANSFER CYCLE
SCLK
I
I
I
I
I
I
I
I
D
D
D
D
D
D
D
D
0
SDIO
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
Figure 60. Serial Port Write Timing—Clock Stall Low
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
SCLK
SDIO
SDO
I
I
I
I
I
I
I
I
0
DON'T CARE
7
6
5
4
3
2
1
D
D
D
D
D
D
D
D
O0
O7
O6
O5
O4
O3
O2
O1
Figure 61. 3-Wire Serial Port Read Timing—Clock Stall Low
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
SCLK
SDIO
I
7
I
I
I
I
I
I
I
D
D
D
D
D
D
D
D
0
6
5
4
3
2
1
0
7
6
5
4
3
2
1
Figure 62. Serial Port Write Timing—Clock Stall High
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
SCLK
SDIO
I
7
I
I
I
I
I
I
I
D
D
D
D
D
D
D
D
O0
6
5
4
3
2
1
0
O7
O6
O5
O4
O3
O2
O1
Figure 63. 2-Wire Serial Port Read Timing—Clock Stall High
Rev. C | Page 48 of 64
Data Sheet
AD9957
For example, if repetitive changes to phase offset via the SPI
I/O_UPDATE, SYNC_CLK, AND SYSTEM CLOCK
RELATIONSHIPS
port is desired, the latency of those changes to the DAC output
is constant; otherwise, a time uncertainty of one SYNC_CLK
period is present.
The I/O_UPDATE pin is used to transfer data from the serial
I/O buffer to the active registers in the device. Data in the buffer
is inactive.
By default, the I/O_UPDATE pin is an input that serves as a
strobe signal to allow synchronous update of the device oper-
ating parameters. A rising edge on I/O_UPDATE initiates
transfer of the register contents to the internal workings of
the device. Alternatively, the transfer of programmed data from
the programming registers to the internal hardware can be
accomplished by changing the state of the PROFILE[2:0] pins.
SYNC_CLK is a rising edge active signal. It is derived from the
system clock and a divide-by-4 frequency divider. SYNC_CLK,
which is externally provided, can be used to synchronize
external hardware to the AD9957 internal clocks.
I/O_UPDATE initiates the start of a buffer transfer. It can
be sent synchronously or asynchronously relative to the
SYNC_CLK. If the setup time between these signals is met,
then constant latency (pipeline) to the DAC output exists.
The timing diagram shown in Figure 64 depicts when the data
in the buffer is transferred to the active registers.
SYSCLK
A
B
SYNC_CLK
I/O_UPDATE
DATA IN
REGISTERS
N
N + 1
N – 1
DATA IN
I/O BUFFERS
N
N + 1
N + 2
THE DEVICE REGISTERS AN I/O UPDATE AT POINT A. THE DATA IS TRANSFERRED FROM THE ASYNCHRONOUSLY LOADED I/O BUFFERS AT POINT B.
Figure 64. I/O_UPDATE Transferring Data from I/O Buffer to Active Registers
Rev. C | Page 49 of 64
AD9957
Data Sheet
REGISTER MAP AND BIT DESCRIPTIONS
REGISTER MAP
Note that the highest number found in the Bit Range column for each register in the following tables is the MSB and the lowest number is
the LSB for that register.
Table 13. Control Registers
Register
Name
(Serial
Bit
Range
(Internal Bit 7
Address) (MSB)
Bit 0
(LSB)
Default
Value
Address)
Bit 6
Bit 5
Open
Bit 4
Bit 3
Bit 2
Open
Bit 1
Control
Function
Register 1
CFR1
<31:24>
RAM
Enable
RAM
Operating Mode
0x00
Playback
Destination
<23:16>
Manual
OSK
Inverse
Sinc Filter
Clear CCI
Open
Select
DDS
0x00
(0x00)
External
Control
Enable
Sine
Output
<15:8>
<7:0>
Open
Autoclear
Phase
Accumulator
Open
Clear Phase
Accumulator I/O Update
Load ARR @
OSK
Enable
Select
Auto-
OSK
0x00
0x00
0x00
Digital
Power-
Down
DAC Power- REFCLK Input Aux DAC
Down
External
Auto
SDIO
LSB First
Power-Down Power-Down Power-Down Power-Down Input
Control
Enable
Only
Control
Function
Register 2
CFR2
<31:24>
Blackfin
Blackfin Bit
Interface Order
Mode
Blackfin
Early Frame
Sync Enable
Open
Enable
Profile
Registers
as ASF
Active
(0x01)
Source
<23:16>
Internal
I/O
SYNC_CLK
Enable
Open
Read
Effective
0x40
Update
Active
FTW
<15:8>
<7:0>
I/O Update Rate Control PDCLK Rate
Control
Data Format PDCLK
Enable
PDCLK
Invert
TxEnable Q-First
0x08
0x20
Invert
Data
Pairing
Open
Data
Sync Timing
Validation
Disable
Open
Assembler
Hold Last
Value
Control
Function
Register 3
CFR3
<31:24>
<23:16>
<15:8>
Open
Open
REFCLK
DRV0<1:0>
Open
Open
VCO SEL<2:0>
Open
0x1F
0x3F
0x40
ICP<2:0>
REFCLK
Input
Divider
PLL
Enable
Input
Divider
(0x02)
Bypass
ResetB
<7:0>
N<6:0>
Open
0x00
0x00
0x00
0x7F
0x7F
Auxiliary
DAC
Control
Register
(0x03)
<31:24>
<23:16>
<15:8>
<7:0>
Open
Open
Open
FSC<7:0>
I/O Update <31:24>
I/O Update Rate<31:24>
I/O Update Rate<23:16>
I/O Update Rate<15:8>
I/O Update Rate<7:0>
0xFF
0xFF
0xFF
0xFF
Rate
<23:16>
Register
<15:8>
(0x04)
<7:0>
Rev. C | Page 50 of 64
Data Sheet
AD9957
Table 14. RAM, ASF, Multichip Sync, and Profile 0 Registers
Bit Range
(Internal
Address)
Register Name
(Serial Address)
Bit 7
(MSB)
Bit
4
Bit 0
(LSB)
Default
Value
Bit 6 Bit5
Bit 3
Bit 2
Bit 1
RAM Segment
Register 0 (0x05)
<47:40>
<39:32>
<31:24>
<23:16>
RAM Address Step Rate 0<15:8>
RAM Address Step Rate 0<7:0>
RAM End Address 0<9:2>
Open
RAM End
Address 0<1:0>
<15:8>
<7:0>
RAM Start Address 0<9:2>
RAM Start
Address 0<1:0>
Open
RAM Playback Mode 0<2:0>
RAM Segment
Register 1 (0x06)
<47:40>
<39:32>
<31:24>
<23:16>
RAM Address Step Rate 1<15:8>
RAM Address Step Rate 1<7:0>
RAM End Address 1<9:2>
Open
RAM End
Address 1<1:0>
<15:8>
<7:0>
RAM Start Address 1<9:2>
RAM Start
Address 1<1:0>
Open
RAM Playback Mode 1<2:0>
Amplitude Scale
Factor (ASF)
Register
<31:24>
<23:16>
<15:8>
<7:0>
Amplitude Ramp Rate<15:8>
0x00
0x00
0x00
0x00
0x00
Amplitude Ramp Rate<7:0>
Amplitude Scale Factor<13:6>
(0x09)
Amplitude Scale Factor<5:0>
Amplitude Step Size<1:0>
Sync Open
Generator
Multichip Sync
Register (0x0A)
<31:24>
Sync Validation Delay<3:0>
Sync
Sync
Receiver
Generator
Enable
Enable
Polarity
<23:16>
<15:8>
<7:0>
Sync State Preset Value<5:0>
Sync Generator Delay<4:0>
Sync Receiver Delay<4:0>
Open
Open
0x00
0x00
0x00
0x08
0xB5
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Open
Open
Profile 0
Register—Single
Tone (0x0E)
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
<7:0>
Amplitude Scale Factor<13:8>
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
Profile 0
Register—QDUC
<63:56>
CCI Interpolation Rate<7:2>
Spectral Invert Inverse
CCI Bypass
(0x0E)
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Output Scale Factor
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Rev. C | Page 51 of 64
AD9957
Data Sheet
Table 15. Profile 1, Profile 2, and Profile 3 Registers
Register
Name
(Serial
Address)
Bit Range
(Internal
Address)
Bit 7
(MSB)
Bit 0
(LSB)
Default
Value
Bit 6
Open
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Profile 1
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Amplitude Scale Factor<13:8>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Register—
Single Tone
(0x0F)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 1
Register—
QDUC (0x0F)
<63:56>
CCI Interpolation Rate<7:2>
Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Output Scale Factor<7:0>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 2
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Open
Amplitude Scale Factor<13:8>
Register—
Single Tone
(0x10)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 2
Register—
<63:56>
CCI Interpolation Rate<7:2>
Spectral
Invert
Inverse CCI
Bypass
QDUC (0x10)
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Output Scale Factor<7:0>
Phase Offset Word<15:8>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 3
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Open
Amplitude Scale Factor<13:8>
Register—
Single Tone
(0x11)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 3
Register—
QDUC
<63:56>
CCI Interpolation Rate<7:2>
Spectral
Invert
Inverse CCI
Bypass
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Output Scale Factor<7:0>
Phase Offset Word<15:8>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
(0x11)
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
Rev. C | Page 52 of 64
<7:0>
Data Sheet
AD9957
Table 16. Profile 4, Profile 5, and Profile 6 Registers
Register
Name
(Serial
Bit
Range
(Internal
Address)
Default
Value
Address)
Bit 7 (MSB)
Open
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Amplitude Scale Factor<13:8>
Bit 0 (LSB)
Profile 4
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Register—
Single Tone
(0x12)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 4
Register—
QDUC
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
CCI Interpolation Rate<7:2>
Spectral Invert
Inverse CCI Bypass
Output Scale Factor<7:0>
Phase Offset Word<15:8>
(0x12)
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 5
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Open
Amplitude Scale Factor<13:8>
Register—
Single Tone
(0x13)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 5
Register—
QDUC
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
CCI Interpolation Rate<7:2>
Spectral Invert
Inverse CCI Bypass
Output Scale Factor<7:0>
Phase Offset Word<15:8>
(0x13)
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 6
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Open
Amplitude Scale Factor<13:8>
Register—
Single Tone
(0x14)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 6
Register—
QDUC
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
CCI Interpolation Rate<7:2>
Spectral Invert
Inverse CCI Bypass
Output Scale Factor<7:0>
Phase Offset Word<15:8>
(0x14)
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
Rev. C | Page 53 of 64
<7:0>
AD9957
Data Sheet
Table 17. Profile 7, RAM, GPIO Configuration, and GPIO Data Registers
Bit Range
Register Name
(Internal
(Serial Address) Address)
Bit 7
(MSB)
Bit 0
(LSB)
Default
Value
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Amplitude Scale Factor<13:8>
Profile 7
<63:56>
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
Open
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Register—
Single Tone
(0x15)
Amplitude Scale Factor<7:0>
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
<7:0>
Profile 7
Register—
QDUC (0x15)
<63:56>
CCI Interpolation Rate<7:2>
Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48>
<47:40>
<39:32>
<31:24>
<23:16>
<15:8>
<7:0>
Output Scale Factor<7:0>
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Phase Offset Word<15:8>
Phase Offset Word<7:0>
Frequency Tuning Word<31:24>
Frequency Tuning Word<23:16>
Frequency Tuning Word<15:8>
Frequency Tuning Word<7:0>
RAM Word<31:0>
RAM Register
(0x16)
<31:0>
GPIO
Configuration
Register (0x18)
<15:0>
<15:0>
GPIO Configuration<15:0>
GPIO Data<15:0>
0x00
0x00
GPIO Data
Register (0x19)
Rev. C | Page 54 of 64
Data Sheet
AD9957
The following section provides a detailed description of each bit
in the AD9957 register map. For cases in which a group of bits
serve a specific function, the entire group is considered as a
binary word and described in aggregate.
REGISTER BIT DESCRIPTIONS
The serial I/O port registers span an address range of 0 to 25
(0x00 to 0x19 in hexadecimal notation). This represents a total
of 26 registers. However, six of these registers are unused, yielding
a total of 20 available registers. The unused registers are 7, 8, 11
to 13, and 23 (0x07 to 0x08, 0x0B to 0x0D, and 0x17).
This section is organized in sequential order of the serial
addresses of the registers. Following each subheading are the
individual bit descriptions for that particular register. The
location of the bit(s) in the register are indicated by <A> or
<A:B>, where A and B are bit numbers. The notation, <A:B>,
specifies a range of bits from most significant to least significant
bit position. For example, <5:2> means bit positions 5 down to
2, inclusive, with Bit 0 identifying the LSB of the register.
The number of bytes assigned to the registers varies. That is, the
registers are not of uniform depth; each contains the number
of bytes necessary for its particular function. Additionally, the
registers are assigned names according to their functionality.
In some cases, a register is given a mnemonic descriptor. For
example, the register at Serial Address 0x00 is named Control
Function Register 1 and is assigned the mnemonic CFR1.
Unless otherwise stated, programmed bits are not transferred to
their internal destinations until the assertion of an I/O update or
profile change.
Control Function Register 1 (CFR1)
Address 0x00, four bytes are assigned to this register.
Table 18. Bit Descriptions for CFR1 Register
Bit (s) Mnemonic
Description
31 RAM Enable
0: disables RAM playback functionality (default).
1: enables RAM playback functionality.
30:29 Open
28
RAM Playback
Destination
Ineffective unless CFR1<31> = 1.
0: RAM playback data routed to baseband scaling multipliers (default).
1: RAM playback data routed to baseband I/Q data path.
27:26 Open
25:24 Operating Mode
00: quadrature modulation mode (default).
01: single tone mode.
1x: interpolating DAC mode.
23
Manual OSK
External Control
Ineffective unless CFR1<9:8> = 10b.
0: OSK pin inoperative (default).
1: OSK pin enabled for manual OSK control (see the Output Shift Keying (OSK) section).
0: inverse sinc filter bypassed (default).
1: inverse sinc filter active.
This bit is automatically cleared by the serial I/O port controller. This operation requires several internal clock
cycles to complete, during which time the data supplied to the CCI input by the baseband signal chain is
ignored. The inputs are forced to all zeros to flush the CCI data path, after which the CCI accumulators are reset.
22
21
Inverse Sinc Filter
Enable
Clear CCI
0: normal operation of the CCI filter (default).
1: initiates an asynchronous reset of the accumulators in the CCI filter.
20:17 Open
16
Select DDS Sine
Output
Ineffective unless CFR1<25:24> = 01b.
0: cosine output of the DDS is selected (default).
1: sine output of the DDS is selected.
15:14 Open
13
Autoclear Phase
0: normal operation of the DDS phase accumulator (default).
Accumulator
1: synchronously resets the DDS phase accumulator any time I/O_UPDATE is asserted or a profile
change occurs.
12
11
Open
Clear Phase
Accumulator
0: normal operation of the DDS phase accumulator (default).
1: asynchronous, static reset of the DDS phase accumulator.
0: normal operation of the OSK amplitude ramp rate timer (default).
1: OSK amplitude ramp rate timer reloaded any time I/O_UPDATE is asserted or a profile change occurs.
Rev. C | Page 55 of 64
10
Load ARR @ I/O
Update
AD9957
Data Sheet
Bit (s) Mnemonic
Description
9
OSK (Output Shift
0: OSK disabled (default).
Keying) Enable
1: OSK enabled.
8
Select Auto-OSK
Ineffective unless CFR1<9> = 1.
0: manual OSK enabled (default).
1: automatic OSK enabled.
7
Digital Power-
Down
This bit is effective without the need for an I/O update.
0: clock signals to the digital core are active (default).
1: clock signals to the digital core are disabled.
0: DAC clock signals and bias circuits are active (default).
1: DAC clock signals and bias circuits are disabled.
This bit is effective without the need for an I/O update.
0: REFCLK input circuits and PLL are active (default).
1: REFCLK input circuits and PLL are disabled.
0: auxiliary DAC clock signals and bias circuits are active (default).
1: auxiliary DAC clock signals and bias circuits are disabled.
0: assertion of the EXT_PWR_DWN pin affects full power-down (default).
1: assertion of the EXT_PWR_DWN pin affects fast recovery power-down.
6
5
DAC Power-Down
REFCLK Input
Power-Down
4
3
2
Auxiliary DAC
Power-Down
External Power-
Down Control
Auto Power-Down Ineffective when CFR1<25:24> = 01b.
Enable
0: disable power-down (default).
1: when the TxEnable pin is Logic 0, the baseband signal processing chain is flushed of residual data and
the clocks are automatically stopped. Clocks restart when the TxENABLE pin is a Logic 1.
1
0
SDIO Input Only
LSB First
0: configures the SDIO pin for bidirectional operation; 2-wire serial programming mode (default).
1: configures the serial data I/O pin (SDIO) as an input only pin; 3-wire serial programming mode.
0: configures the serial I/O port for MSB first format (default).
1: configures the serial I/O port for LSB first format.
Control Function Register 2 (CFR2)
Address 0x01, four bytes are assigned to this register.
Table 19. Bit Descriptions for CFR2 Register
Bit (s) Mnemonic
Description
31
Blackfin Interface
Mode Active
Valid only when CFR1<25:24> = 00b (quadrature modulation mode).
0: Pin D<17:0> configured as an 18-bit parallel port (default).
1: Pin D<5:4> configured as a dual serial port compatible with the Blackfin serial interface. Pin D<17:6>
and Pin D<3:0> become available as a 16-bit GPIO port.
30
29
Blackfin Bit Order
Valid only when CFR2<31> = 1.
0: the dual serial port (BFI) configured for MSB first operation (default).
1: the dual serial port (BFI) configured for LSB first operation.
Valid only when CFR2<31> = 1.
0: the dual serial port (BFI) configured to be compatible with Blackfin late frame sync operation (default).
1: the dual serial port (BFI) configured to be compatible with Blackfin early frame sync operation.
Blackfin Early
Frame Sync
Enable
28:25 Open
24
Enable Profile
Registers as ASF
Source
Valid only when CFR1<25:24> = 01b (single tone mode) and CFR1<9>=0 (OSK disabled).
0: amplitude scale factor bypassed (unity gain).
1: the active profile register determines the amplitude scale factor.
This bit is effective without the need for an I/O update.
23
Internal I/O
Update Active
0: serial I/O programming is synchronized with external assertion of the I/O_UPDATE pin, which is
configured as an input pin (default).
1: serial I/O programming is synchronized with an internally generated I/O update signal (the internally
generated signal appears at the I/O_UPDATE pin, which is configured as an output pin).
22
SYNC_CLK Enable
0: the SYNC_CLK pin is disabled; static Logic 0 output.
1: the SYNC_CLK pin generates a clock signal at ¼ fSYSCLK; use of synchronization of the serial I/O port
(default).
Rev. C | Page 56 of 64
Data Sheet
AD9957
Bit (s) Mnemonic
Description
21:17 Open
16
Read Effective
FTW
0: a serial I/O port read operation of the FTW register reports the contents of the FTW register (default).
1: a serial I/O port read operation of the FTW register reports the actual 32-bit word appearing at the input to
the DDS phase accumulator.
15:14 I/O Update Rate
Control
Ineffective unless CFR2<23> = 1. Sets the prescale ratio of the divider that clocks the I/O update timer as
follows:
00: divide-by-1 (default).
01: divide-by-2.
10: divide-by-4.
11: divide-by-8.
13
PDCLK Rate
Control
Ineffective unless CFR2<31> = 0 and CFR1<25:24> = 00b.
0: PDCLK operates at the input data rate (default).
1: PDCLK operates at ½ the input data rate; useful for maintaining a consistent relationship between I/Q
words at the parallel data port and the internal clocks of the baseband signal processing chain.
12
11
Data Format
0: the data-words applied to Pin D<17:0> are expected to be coded as twos complement (default).
1: the data-words applied to Pin D<17:0> are expected to be coded as offset binary.
0: the PDCLK pin is disabled and forced to a static Logic 0 state; the internal clock signal continues to operate
and provide timing to the data assembler.
PDCLK Enable
1: the internal PDCLK signal appears at the PDCLK pin (default).
0: normal PDCLK polarity; Q-data associated with Logic 1, I-data with Logic 0 (default).
1: inverted PDCLK polarity.
0: normal TxENABLE polarity; Logic 0 is standby, Logic 1 is transmit (default).
1: inverted TxENABLE polarity; Logic 0 is transmit, Logic 1 is standby.
0: an I/Q data pair is delivered as I-data first, followed by Q-data (default).
1: an I/Q data pair is delivered as Q-data first, followed by I-data.
10
9
PDCLK Invert
TxEnable Invert
8
Q-First Data
Pairing
7
6
Open
Data Assembler
Hold Last Value
Ineffective when CFR1<25:24> = 01b.
0: when the TxENABLE pin is false, the data assembler ignores the input data and internally forces zeros on
the baseband signal path (default).
1: when the TxENABLE pin is false, the data assembler ignores the input data and internally forces the last
value received on the baseband signal path.
5
Sync Timing
Validation Disable
0: enables the setup and hold validation circuit to take a measurement; the measurement result appears at
the SYNC_SMP_ERR pin; a Logic 1 at this pin indicates a potential setup/hold violation whereas a Logic 0
indicates that a setup/hold violation has not been detected; the measurement result is latched and held until
this bit is set to a Logic 1.
1: resets the setup and hold validation measurement circuit forcing the SYNC_SMP_ERR pin to a static Logic 0
condition (default); the measurement circuit is effectively disabled until this bit is restored to a Logic 0 state.
4:0
Open
Rev. C | Page 57 of 64
AD9957
Data Sheet
Control Function Register 3 (CFR3)
Address 0x02, four bytes are assigned to this register.
Table 20. Bit Descriptions for CFR3 Register
Bit (s)
31:30
29:28
27
Mnemonic
Description
Open
DRV0
Open
Controls REFCLK_OUT pin (see Table 6 for details); default is 01b.
26:24
23:22
21:19
18:16
15
VCO SEL
Open
ICP
Open
REFCLK Input Divider
Bypass
Selects frequency band of the VCO in the REFCLK PLL (see Table 7 for details); default is 111b.
Selects the charge pump current in the REFCLK PLL (see Table 8 for details); default is 111b.
0: input divider is selected (default).
1: input divider is bypassed.
14
REFCLK Input Divider
ResetB
0: input divider is reset.
1: input divider operates normally (default).
13:9
8
Open
PLL Enable
0: REFCLK PLL bypassed (default).
1: REFCLK PLL enabled.
7:1
0
N
Open
This 7-bit number is divide modulus of the REFCLK PLL feedback divider; default is 0000000b.
Auxiliary DAC Control Register
Address 0x03, four bytes are assigned to this register.
Table 21. Bit Descriptions for Auxiliary DAC Control Register
Bit(s)
31:8
7:0
Mnemonic
Description
Open
FSC
This 8-bit number controls the full-scale output current of the main DAC (see the Auxiliary DAC section);
default is 0xFF.
I/O Update Rate Register
Address 0x04, four bytes are assigned to this register. This register is effective without the need for an I/O update.
Table 22. Bit Descriptions for I/O Update Rate Register5
Bit(s) Mnemonic
Description
31:0
I/O Update Rate
Ineffective unless CFR2<23> = 1. This 32-bit number controls the automatic I/O update rate (see the
Automatic I/O Update section); default is 0xFFFFFFFF.
RAM Segment Register 0
Address 0x05, six bytes are assigned to this register. This register is effective without the need for an I/O update. This register is only
active if CFR1<31> = 1 and there is a Logic 0-to-Logic 1 transition on the RT pin.
Table 23. Bit Descriptions for RAM Segment Register 0
Bit(s)
Mnemonic
Description
47:32
RAM Address Step
Rate 0
This 16-bit number controls the rate at which the RAM state machine steps through the specified RAM
address range.
31:22
21:16
15:6
5:3
RAM End Address 0
Open
RAM Start Address 0
Open
This 10-bit number identifies the ending address for the RAM state machine.
This 10-bit number identifies the starting address for the RAM state machine.
This 3-bit number identifies the playback mode for the RAM state machine (see Table 5).
2:0
RAM Playback Mode 0
Rev. C | Page 58 of 64
Data Sheet
AD9957
RAM Segment Register 1
Address 0x06, six bytes are assigned to this register. This register is only active if CFR1<31> = 1 and there is a Logic 1 to Logic 0 transition
on the RT pin.
Table 24. Bit Descriptions for RAM Segment Register 1
Bit(s)
Mnemonic
Description
47:32
RAM Address Step
Rate 1
This 16-bit number controls the rate at which the RAM state machine steps through the specified RAM
address range.
31:22
21:16
15:6
5:3
RAM End Address 1
Open
RAM Start Address 1
Open
This 10-bit number identifies the ending address for the RAM state machine.
This 10-bit number identifies the starting address for the RAM state machine.
This 3-bit number identifies the playback mode for the RAM state machine (see Table 5).
2:0
RAM Playback Mode 1
Amplitude Scale Factor (ASF) Register
Address 0x09, four bytes are assigned to this register. This register is only active if CFR1<9> = 1.
Table 25. Bit Descriptions for ASF Register
Bit(s)
Mnemonic
Description
31:16
Amplitude Ramp Rate
Ineffective unless CFR1<8> = 1. This 16-bit number controls the rate at which the OSK controller
updates amplitude changes to the DDS.
15:2
1:0
Amplitude Scale Factor If CFR1<8> = 0 and CFR1<23> = 0, then this 14-bit number is the amplitude scale factor for the DDS.
If CFR1<8> = 0 and CFR1<23> = 1, then this 14-bit number is the amplitude scale factor for the DDS
when the OSK pin is Logic 1.
If CFR1<8> = 1, then this 14-bit number sets a ceiling on the maximum allowable amplitude scale factor
for the DDS.
Amplitude Step Size
Ineffective unless CFR1<8> = 1. This 2-bit number controls the step size for amplitude changes to the
DDS (see Table 9).
Multichip Sync Register
Address 0x0A, four bytes are assigned to this register.
Table 26. Bit Descriptions for the Multichip Sync Register
Bit(s) Mnemonic
Description
31:28 Sync Validation Delay
Default is 0000b. This 4-bit number sets the timing skew (in ~75 ps increments) between SYSCLK and
the delayed sync-in signal for the synchronization validation block in the synchronization receiver.
27
26
25
24
Sync Receiver Enable
Sync Generator Enable
Sync Generator Polarity
Open
0: synchronization clock receiver disabled (default).
1: synchronization clock receiver enabled.
0: synchronization clock generator disabled (default).
1: synchronization clock generator enabled.
0: synchronization clock generator coincident with the rising edge of the system clock (default).
1: synchronization clock generator coincident with the falling edge of the system clock.
23:18 Sync State Preset Value
Default is 000000b. This 6-bit number is the state that the internal clock generator assumes when it
receives a sync pulse.
17:16 Open
15:11 Sync Generator Delay
Default is 00000b. This 5-bit number sets the output delay (in ~75 ps increments) of the synchronization
generator.
10:8
7:3
Open
Sync Receiver Delay
Default is 00000b. This 5-bit number sets the delay input delay (in ~75 ps increments) of the
synchronization receiver.
2:0
Open
Rev. C | Page 59 of 64
AD9957
Data Sheet
QDUC profiles control: DDS frequency (32 bits), DDS phase
offset (16 bits), output amplitude scaling (8 bits), CCI filter
interpolation factor, inverse CCI bypass, and spectral invert.
The QDUC profiles also selectively apply to the interpolating
DAC operating mode: only output scaling, CCI filter interpola-
tion factor, and inverse CCI bypass apply; all others (DDS
frequency, output amplitude scaling, and spectral invert) are
ignored.
PROFILE REGISTERS
There are eight consecutive serial I/O addresses (0x0E to 0x15)
dedicated to device profiles. All eight profile registers are either
single tone profiles or QDUC profiles depending on the device
operating mode specified by CFR1<25:24>. During operation,
the active profile register is determined via the external
PROFILE<2:0> pins.
Single tone profiles control: DDS frequency (32 bits), DDS
phase offset (16 bits), and DDS amplitude scaling (14 bits).
Profile<7:0> Register—Single Tone
Address 0x0E to 0x15, eight bytes are assigned to this register.
Table 27. Bit Descriptions for Profile<7:0> Registers—Single Tone
Bit(s)
63:62
61:48
47:32
31:0
Mnemonic
Description
Open
Amplitude Scale Factor
Phase Offset Word
Frequency Tuning Word
This 14-bit number controls the DDS output amplitude.
This 16-bit number controls the DDS phase offset.
This 32-bit number controls the DDS frequency.
Profile<7:0> Register—QDUC
Address 0x0E to 0x15, eight bytes are assigned to this register.
Table 28. Bit Descriptions for Profile<7:0> Registers—QDUC
Bit(s)
63:58
57
Mnemonic
Description
CC Interpolation Rate
Spectral Invert
This 6-bit number is the rate interpolation factor for the CCI filter.
0: the modulator output takes the form: I(t) × cos(ct) – Q(t) × sin(ct).
1: the modulator output takes the form: I(t) × cos(ct) + Q(t) × sin(ct).
0: the inverse CCI filter is enabled.
56
Inverse CCI Bypass
1: the inverse CCI filter is bypassed.
55:48
47:32
31:0
Output Scale Factor
Phase Offset Word
Frequency Tuning Word
This 8-bit number controls the output amplitude.
This 16-bit number controls the DDS phase offset.
This 32-bit number controls the DDS frequency.
RAM Register
Address 0x16, four bytes are assigned to this register.
Table 29. Bit Descriptions for RAM Register
Bit(s)
Mnemonic
Description
31:0
RAM Word
The number of 32-bit words written to RAM is defined by the start and end address in
RAM Segment Register 0 or RAM Segment Register 1.
GPIO Configuration Register
Address 0x18, two bytes are assigned to this register.
Table 30. Bit Descriptions for GPIO Configuration Register
Bit(s)
Mnemonic
Description
15:0
GPIO Configuration
See the General-Purpose I/O (GPIO) Port section for details.
GPIO Data Register
Address 0x19, two bytes are assigned to this register.
Table 31. Bit Descriptions for GPIO Data Register
Bits
Mnemonic
Description
15:0
GPIO Data
Read or write based on the contents of the GPIO Configuration register. See the
General-Purpose I/O (GPIO) Port section for details.
Rev. C | Page 60 of 64
Data Sheet
AD9957
OUTLINE DIMENSIONS
16.00 BSC SQ
1.20
MAX
0.75
0.60
0.45
14.00 BSC SQ
76
76
75
100
100
1
75
1
PIN 1
EXPOSED
PAD
5.00 SQ
TOP VIEW
(PINS DOWN)
0° MIN
1.05
1.00
0.95
0.20
0.09
7°
BOTTOM VIEW
(PINS UP)
51
51
25
25
26
50
50
26
3.5°
0°
0.50 BSC
LEAD PITCH
0.27
0.22
0.17
VIEW A
0.15
0.05
SEATING
PLANE
0.08 MAX
COPLANARITY
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
VIEW A
ROTATED 90° CCW
SECTION OF THIS DATA SHEET.
COMPLIANT TO JEDEC STANDARDS MS-026-AED-HD
Figure 65. 100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
(SV-100-4)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
AD9957BSVZ
AD9957BSVZ-REEL
AD9957/PCBZ
Temperature Range
−40°C to +85°C
−40°C to +85°C
Package Description
Package Option
SV-100-4
SV-100-4
100-Lead Thin Quad Flat Package Exposed Pad [TQFP_EP]
100-Lead Thin Quad Flat Package Exposed Pad [TQFP_EP]
Evaluation Board
1 Z = RoHS Compliant Part.
Rev. C | Page 61 of 64
AD9957
NOTES
Data Sheet
Rev. C | Page 62 of 64
Data Sheet
NOTES
AD9957
Rev. C | Page 63 of 64
AD9957
NOTES
Data Sheet
©2007–2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D06384-0-4/12(C)
Rev. C | Page 64 of 64
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