AD9954_17 [ADI]
400MSPS, 14-Bit, 1.8 V CMOS Direct Digital Synthesizer;
| 型号： | AD9954_17 |
| 厂家： | 
ADI |
| 描述： | 400MSPS, 14-Bit, 1.8 V CMOS Direct Digital Synthesizer |
| 文件： | 总40页 (文件大小：742K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
400 MSPS, 14-Bit, 1.8 V CMOS,
Direct Digital Synthesizer
Data Sheet
AD9954
FEATURES
GENERAL DESCRIPTION
400 MSPS internal clock speed
Integrated 14-bit DAC
Programmable phase/amplitude dithering
32-bit frequency tuning accuracy
14-bit phase tuning accuracy
Phase noise better than –120 dBc/Hz
Excellent dynamic performance
>80 dB narrowband SFDR
The AD9954 is a direct digital synthesizer (DDS) that uses
advanced technology, coupled with an internal high speed, high
performance DAC to form a complete, digitally programmable,
high frequency synthesizer capable of generating a frequency-
agile analog output sinusoidal waveform at up to 160 MHz.
The AD9954 enables fast frequency hopping coupled with fine
tuning of both frequency (0.01 Hz or better) and phase (0.022°
granularity).
Serial input/output (I/O) control
Ultrahigh speed analog comparator
Automatic linear and nonlinear frequency sweeping
4 frequency/phase offset profiles
1.8 V power supply
Software and hardware controlled power-down
48-lead TQFP
Integrated 1024 word × 32-bit RAM
PLL-based REFCLK multiplier
The AD9954 is programmed via a high speed serial I/O port.
The device includes static RAM to support flexible frequency
sweep capability in several modes, plus a user-defined linear
sweep mode of operation. Also included is an on-chip high
speed comparator for applications requiring a square wave
output. An on-chip oscillator and PLL circuitry provide users
with multiple approaches to generate the device’s system clock.
The AD9954 is specified to operate over the extended industrial
temperature range (see Table 2).
Internal oscillator, can be driven by a single crystal
Phase modulation capability
Multichip synchronization
APPLICATIONS
Agile LO frequency synthesis
Programmable clock generators
FM chirp source for radar and scanning systems
Automotive radars
Test and measurement equipment
Acousto-optic device drivers
BASIC BLOCK DIAGRAM
AD9954
DIGITAL
SINE
WAVE
14-BIT
DAC
400MSPS
DDS CORE
COMPARATOR
REF CLOCK
INPUT CIRCUITRY
TIMING AND
CONTROL
USER INTERFACE
Figure 1.
Rev. C
Document Feedback
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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 registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2003–2017 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
AD9954
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Serial Interface Port Pin Descriptions ..................................... 24
MSB/LSB Transfers .................................................................... 24
RAM I/O via Serial Port............................................................ 24
Instruction Byte.......................................................................... 25
Register Maps and Descriptions............................................... 25
Control Register Bit Descriptions............................................ 29
Other Register Descriptions ..................................................... 31
Layout Considerations............................................................... 32
Detailed Programming Examples ................................................ 33
Single-Tone Mode ...................................................................... 33
Linear Sweep Mode.................................................................... 33
RAM Mode.................................................................................. 33
Suggested Application Circuits..................................................... 35
Evaluation Board Schematics........................................................ 36
Outline Dimensions....................................................................... 39
Ordering Guide .......................................................................... 39
Applications....................................................................................... 1
General Description......................................................................... 1
Basic Block Diagram ........................................................................ 1
Revision History ............................................................................... 2
Functional Block Diagram .............................................................. 3
Electrical Specifications ................................................................... 4
Absolute Maximum Ratings............................................................ 7
Explanation of Test Levels........................................................... 7
ESD Caution.................................................................................. 7
Pin Configuration and Function Descriptions............................. 8
Typical Performance Characteristics ........................................... 10
Theory of Operation ...................................................................... 13
Component Blocks..................................................................... 13
Modes of Operation ................................................................... 16
Synchronization—Register Updates (I/O UPDATE) ............ 21
Serial Port Operation ................................................................. 23
REVISION HISTORY
2/2017—Rev. B to Rev. C
Changes to Modes of Operation Section and Table 8 ............... 16
Changes to Table 9.......................................................................... 17
Changes to Synchronization; Register Updates (I/O UPDATE)
Section and Figure 24..................................................................... 21
Changes to Serial Port Operation Section .................................. 23
Changes to Serial Interface Port Pin Description Section,
MSB/LSB Transfers Section, and RAM I/O Via Serial Port
Section.............................................................................................. 24
Inserted Figure 29 and Figure 30; Renumbered Sequentially .. 24
Changes to Instruction Byte Section, Register Maps and
Changes to Features Section............................................................ 1
5/2009—Rev. A to Rev. B
Changes to Figure 29 and Figure 30............................................. 24
Changes to Table 12........................................................................ 26
Changes to Figure 34...................................................................... 35
Updated Outline Dimensions....................................................... 39
Changes to Ordering Guide .......................................................... 39
1/2007—Rev. 0 to Rev. A
Descriptions Section, and Table 12.............................................. 25
Changes to Table 13 ....................................................................... 26
Changes to Table 14 ....................................................................... 28
Added Single-Tone Mode Section, Linear Sweep Mode Section,
Table 15, and RAM Mode Section ............................................... 33
Added, and Table 16....................................................................... 34
Inserted Figure 35........................................................................... 36
Inserted Figure 36........................................................................... 37
Inserted Figure 37........................................................................... 38
Updated Outline Dimensions....................................................... 39
Changes to Ordering Guide.......................................................... 39
Changes to Layout ..............................................................Universal
Changes to Features, General Description, and Figure 1............ 1
Changes to Figure 2.......................................................................... 3
Changes to Table 1 ............................................................................ 4
Changes to Table 4 ............................................................................ 8
Changes to Figure 5 to Figure 10.................................................. 10
Changes to Figure 12...................................................................... 11
Changes to Figure 17 to Figure 18 Captions ............................... 12
Deleted Figure 19; Renumbered Sequentially............................. 12
Added Table 5; Renumbered Sequentially .................................. 13
Changes to Component Block Section and Table 6................... 13
Changes to Figure 20...................................................................... 15
10/2003—Revision 0: Initial Version
Rev. C | Page 2 of 40
Data Sheet
AD9954
FUNCTIONAL BLOCK DIAGRAM
FREQUENCY
DDS CORE
AD9954
ACCUMULATOR
32
PHASE
M
U
X
ACCUMULATOR
RAM
DAC_R
PHASE
OFFSET
SET
DATA
–1
Z
STATIC RAM
1024 × 32
IOUT
IOUT
32
32
19
14
32
COS(X)
DAC
14
SYSTEM
CLOCK
14
–1
Z
DDS
CLOCK
32
MUX
SYNC_IN
OSK
3
32
10
14
RAM DATA
<31:18>
θ
TIMING AND CONTROL LOGIC
I/O UPDATE
SYNC_CLK
PWRDWNCTL
0
M
U
X
SYNC
CONTROL REGISTERS
÷4
COMPARATOR
OSCILLATOR/BUFFER
COMP_IN
COMP_IN
M
U
X
SYSTEM
CLOCK
4× TO 20×
CLOCK
MULTIPLIER
REFCLK
REFCLK
COMP_OUT
ENABLE
CRYSTAL OUT
PS<1:0> I/O PORT
RESET
Figure 2.
Rev. C | Page 3 of 40
AD9954
Data Sheet
ELECTRICAL SPECIFICATIONS
Unless otherwise noted, AVDD, DVDD = 1.8 V 5%, DVDD_I/O = 3.3 V 5%, RSET = 3.92 kΩ, external reference clock frequency =
400 MHz. DAC output must be referenced to AVDD, not AGND.
Table 1.
Test
Parameter
Temp Level Min
Typ
Max
Unit
REF CLOCK INPUT CHARACTERISTICS
Frequency Range
REFCLK Multiplier Disabled
REFCLK Multiplier Enabled at 4×
REFCLK Multiplier Enabled at 20×
Crystal Oscillator Operating Frequency
Input Capacitance
Full
Full
Full
Full
25°C
25°C
25°C
25°C
Full
VI
VI
VI
IV
V
V
V
V
IV
1
20
4
400
100
20
MHz
MHz
MHz
MHz
pF
kΩ
%
%
mV p-p
20
30
3
1.5
50
Input Impedance
Duty Cycle
Duty Cycle with REFCLK Multiplier Enabled
REFCLK Input Voltage Swing
DAC OUTPUT CHARACTERISTICS
Full-Scale Output Current
Gain Error
Output Offset
Differential Nonlinearity
Integral Nonlinearity
Output Capacitance
35
100
65
1000
25°C
25°C
25°C
25°C
25°C
25°C
5
–10
10
15
+10
0.6
mA
%FS
µA
LSB
LSB
pF
I
I
V
V
V
1
2
5
Residual Phase Noise @ 1 kHz Offset, 40 MHz AOUT
REFCLK Multiplier Enabled @ 20×
REFCLK Multiplier Enabled @ 4×
REFCLK Multiplier Disabled
Voltage Compliance Range
Wideband SFDR
25°C
25°C
25°C
25°C
V
V
V
I
–105
–115
–132
dBc/Hz
dBc/Hz
dBc/Hz
V
AVDD – 0.5
AVDD + 0.5
1 MHz to 10 MHz Analog Out
10 MHz to 40 MHz Analog Out
40 MHz to 80 MHz Analog Out
80 MHz to 120 MHz Analog Out
120 MHz to 160 MHz Analog Out
Narrow-Band SFDR
25°C
25°C
25°C
25°C
25°C
V
V
V
V
V
73
67
62
58
52
dBc
dBc
dBc
dBc
dBc
40 MHz Analog Out ( 1 MHz)
40 MHz Analog Out ( 250 kHz)
40 MHz Analog Out ( 50 kHz)
40 MHz Analog Out ( 10 kHz)
80 MHz Analog Out ( 1 MHz)
80 MHz Analog Out ( 250 kHz)
80 MHz Analog Out ( 50 kHz)
80 MHz Analog Out ( 10 kHz)
120 MHz Analog Out ( 1 MHz)
120 MHz Analog Out ( 250 kHz)
120 MHz Analog Out ( 50 kHz)
120 MHz Analog Out ( 10 kHz)
160 MHz Analog Out ( 1 MHz)
160 MHz Analog Out ( 250 kHz)
160 MHz Analog Out ( 50 kHz)
160 MHz Analog Out ( 10 kHz)
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
25°C
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
87
89
91
93
85
87
89
91
83
85
87
89
81
83
85
87
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
Rev. C | Page 4 of 40
Data Sheet
AD9954
Test
Parameter
Temp Level Min
Typ
Max
Unit
COMPARATOR INPUT CHARACTERISTICS
Input Capacitance
Input Resistance
Input Current
Hysteresis
25°C
25°C
25°C
25°C
V
IV
I
3
500
12
pF
kΩ
µA
mV
IV
30
45
COMPARATOR OUTPUT CHARACTERISTICS
Logic 1 Voltage, High-Z Load
Logic 0 Voltage, High-Z Load
Propagation Delay
Output Duty-Cycle Error
Rise/Fall Time, 5 pF Load
Toggle Rate, High-Z Load
Output Jitter1
Full
Full
VI
VI
IV
IV
IV
IV
IV
1.6
V
V
ns
%
ns
MHz
ps rms
0.4
25°C
25°C
25°C
25°C
25°C
3
5
1
1
200
COMPARATOR NARROW-BAND SFDR
10 MHz to 160 MHz FOUT
Measured over a 1 MHz BW
Measured over a 250 kHz BW
Measured over a 50 kHz BW
Measured over a 10 Hz BW
25°C
25°C
25°C
25°C
V
V
V
V
80
85
90
95
dBc
dBc
dBc
dBc
TIMING CHARACTERISTICS
Serial Control Bus
Maximum Frequency
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
25
2
Mbps
ns
ns
ns
ns
ns
ns
ns
ms
Minimum Clock Pulse Width Low
Minimum Clock Pulse Width High
Maximum Clock Rise/Fall Time
Minimum Data Setup Time DVDD_I/O = 3.3 V
Minimum Data Setup Time DVDD_I/O = 1.8 V
Minimum Data Hold Time
Maximum Data Valid Time
Wake-Up Time2
Minimum Reset Pulse Width High
7
7
3
5
0
25
1
5
SYSCLK
cycles3
I/O UPDATE, PS0, PS1 to SYNC_CLK Setup Time, DVDD_I/O = 3.3 V
I/O UPDATE, PS0, PS1 to SYNC_CLK Setup Time, DVDD_I/O = 1.8 V
I/O UPDATE, PS0, PS1 to SYNC_CLK Hold Time
Latency
Full
Full
Full
I
I
I
4
6
0
ns
ns
ns
I/O UPDATE to Frequency Change Prop Delay
25°C
25°C
25°C
25°C
25°C
25°C
IV
IV
IV
IV
IV
IV
24
24
16
28
28
28
SYSCLK
cycles
SYSCLK
cycles
SYSCLK
cycles
SYSCLK
cycles
SYSCLK
cycles
SYSCLK
cycles
I/O UPDATE to Phase Offset Change Prop Delay
I/O UPDATE to Amplitude Change Prop Delay
PS0, PS1 to RAM Driven Frequency Change Prop Delay
PS0, PS1 to RAM Driven Phase Change Prop Delay
PS0 to Linear Frequency Sweep Prop Delay
Rev. C | Page 5 of 40
AD9954
Data Sheet
Test
Parameter
Temp Level Min
Typ
Max
Unit
CMOS LOGIC INPUTS
Logic 1 Voltage @ DVDD_I/O (Pin 43) = 1.8 V
Logic 0 Voltage @ DVDD_I/O (Pin 43) = 1.8 V
Logic 1 Voltage @ DVDD_I/O (Pin 43) = 3.3 V
Logic 0 Voltage @ DVDD_I/O (Pin 43) = 3.3 V
Logic 1 Current
25°C
25°C
25°C
25°C
25°C
25°C
25°C
I
I
I
I
V
V
V
1.25
2.2
V
V
V
V
µA
µA
pF
0.6
0.8
12
12
3
2
Logic 0 Current
Input Capacitance
CMOS LOGIC OUTPUTS (1 mA Load) DVDD_I/O = 1.8 V
Logic 1 Voltage
Logic 0 Voltage
CMOS LOGIC OUTPUTS (1 mA Load) DVDD_I/O = 3.3 V
Logic 1 Voltage
Logic 0 Voltage
25°C
25°C
I
I
1.35
2.8
V
V
0.4
0.4
25°C
25°C
I
I
V
V
POWER CONSUMPTION (AVDD = DVDD = 1.8 V)
Single-Tone Mode (Comparator Off)
With RAM or Linear Sweep Enabled
With Comparator Enabled
With RAM and Comparator Enabled
Rapid Power-Down Mode
25°C
25°C
25°C
25°C
25°C
25°C
I
I
I
I
I
I
162
175
180
198
150
20
171
190
190
220
160
27
mW
mW
mW
mW
mW
mW
Full-Sleep Mode
SYNCHRONIZATION FUNCTION4
Maximum Sync Clock Rate (DVDD_I/O = 1.8 V)
Maximum Sync Clock Rate (DVDD_I/O = 3.3 V)
SYNC_CLK Alignment Resolution5
25°C
25°C
25°C
VI
VI
V
62.5
100
MHz
MHz
SYSCLK
cycles
1
1 Represents the cycle-to-cycle residual jitter from the comparator alone.
2 Wake-up time refers to the recovery from analog power-down modes (see section on Power-Down Modes of Operation). The primary limiting factor is the settling time of the PLL
multiplier in the reference circuitry. The wake-up time assumes there is no capacitor on DAC BP and that the recommended PLL loop filter values are used.
3 SYSCLK cycle refers to the clock frequency used on-chip to drive the DDS core. This is equal to the frequency of the reference source times the value of the PLL-based
reference clock multiplier.
4 SYNC_CLK = ¼ SYSCLK rate. Be sure the high speed sync enable bit, CFR2<11>, is programmed appropriately.
5 This parameter indicates that the digital synchronization feature cannot compensate for phase delays (timing skew) between system clock rising edges. If the system
clock edges are aligned, the synchronization function should not increase the skew between the two edges.
Rev. C | Page 6 of 40
Data Sheet
AD9954
ABSOLUTE MAXIMUM RATINGS
Table 2.
EXPLANATION OF TEST LEVELS
I
100% production tested.
Parameter
Rating
II
100% production tested at 25°C and sample tested at
specified temperatures.
Maximum Junction Temperature
DVDD_I/O (Pin 43)
150°C
4 V
III
Sample tested only.
AVDD, DVDD
2 V
IV
Parameter is guaranteed by design and characterization
testing.
Parameter is a typical value only.
Devices are 100% production tested at 25°C and
guaranteed by design and characterization testing
for industrial operating temperature range.
Digital Input Voltage (DVDD_I/O = 3.3 V)
Digital Input Voltage (DVDD_I/O = 1.8 V)
Digital Output Current
Storage Temperature Range
Operating Temperature Range
Lead Temperature (10 sec Soldering)
θJA
–0.7 V to +5.25 V
–0.7 V to +2.2 V
5 mA
–65°C to +150°C
–40°C to +105°C
300°C
V
VI
38°C/W
ESD CAUTION
θJC
15°C/W
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
DIGITAL
INPUTS
DIGITAL
OUTPUTS
COMPARATOR
INPUTS
COMPARATOR
OUTPUT
IOUT
IOUT
DVDD_I/O
AVDD
INPUT
COMP IN
COMP IN
AVOID OVERDRIVING
DIGITAL INPUTS.
MUST TERMINATE
OUTPUTS TO AVDD FOR
CURRENT FLOW. DO
NOT EXCEED THE
FORWARD BIASING
ESD DIODES MAY
COUPLE DIGITAL NOISE
ONTO POWER PINS.
OUTPUT VOLTAGE
COMPLIANCE RATING.
Figure 3. Equivalent Input and Output Circuits
Rev. C | Page 7 of 40
AD9954
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
48 47 46 45 44 43 42 41 40 39 38 37
1
36
35
34
33
32
31
30
29
28
27
26
25
RESET
I/O UPDATE
PIN 1
2
3
DVDD
DGND
PWRDWNCTL
DVDD
4
DGND
AVDD
5
AGND
AGND
AD9954
TOP VIEW
(Not to Scale)
6
AVDD
COMP_IN
COMP_IN
AVDD
7
AGND
8
OSC/REFCLK
OSC/REFCLK
CRYSTAL OUT
CLKMODESELECT
LOOP_FILTER
9
COMP_OUT
AVDD
10
11
12
AGND
AVDD
13 14 15 16 17 18 19 20 21 22 23 24
Figure 4. Pin Configuration
Note that the exposed paddle on the bottom of the package forms an electrical connection for the DAC and must be attached to
analog ground. Note that Pin 43, DVDD_I/O, can be powered to 1.8 V or 3.3 V. The DVDD pins (Pin 2 and Pin 34) must be
powered to 1.8 V.
Table 3. Pin Function Descriptions
Pin No.
Mnemonic
I/O Description
1
I/O UPDATE
I
The rising edge transfers the contents of the internal buffer memory to the I/O registers.
See Synchronization—Register Updates (I/O UPDATE) section for details.
2, 34
3, 33, 42
4, 6, 13, 16, AVDD
18, 19, 25,
DVDD
DGND
I
I
I
Digital Power Supply Pins (1.8 V).
Digital Power Ground Pins.
Analog Power Supply Pins (1.8 V).
27, 29
5, 7, 14, 15, AGND
17, 22, 26,
32
I
I
Analog Power Ground Pins.
8
OSC/REFCLK
Oscillator Input/Complementary Reference Clock. When the REFCLK port is operated in
single-ended mode, REFCLK should be decoupled to AVDD with a 0.1 µF capacitor.
9
10
11
OSC/REFCLK
CRYSTAL OUT
CLKMODESELECT
I
O
I
Oscillator Input/Reference Clock. See Table 5 for details on the OSC/REFCLK operation.
Output of the Oscillator Section.
Control Pin for the Oscillator Section (1.8 V logic only). See REFCLK Input section for detailed
instructions.
12
LOOP_FILTER
I
This pin provides the connection for the external zero compensation network of the REFCLK
multiplier’s PLL loop filter. The network varies based on the multiplication value in the PLL loop.
See Table 4 for details.
20
21
23
24
IOUT
O
O
I
Complementary DAC Output. Should be biased through a resistor to AVDD, not AGND.
DAC Output. Should be biased through a resistor to AVDD, not AGND.
DAC Band Gap Decoupling Pin. A 0.1 μF capacitor to AGND is recommended.
A resistor (3.92 kΩ nominal) connected from AGND to DAC_RSET establishes the reference
current for the DAC. See equation in DAC Output section.
IOUT
DACBP
DAC_RSET
I
28
30
COMP_OUT
COMP_IN
O
I
Comparator Output.
Comparator Input.
Rev. C | Page 8 of 40
Data Sheet
AD9954
Pin No.
31
Mnemonic
I/O Description
COMP_IN
PWRDWNCTL
RESET
I
I
I
Comparator Complementary Input.
Input Pin Used as an External Power-Down Control (see Table 9 for details).
Active High Hardware Reset Pin. Assertion of the RESET pin forces the AD9954 to the default
state, as described in the right-hand column of Table 12, which is the I/O port register map.
35
36
37
IOSYNC
I
Asynchronous Active High Reset of the Serial Port Controller. When high, the current I/O
operation is immediately terminated, enabling a new I/O operation to commence once
IOSYNC is returned low. If unused, ground this pin; do not allow this pin to float.
38
39
40
41
43
44
SDO
CS
O
I
See Serial Interface Port Pin Description section for details.
See Serial Interface Port Pin Description section for details.
See Serial Interface Port Pin Description section for details.
SCLK
SDIO
DVDD_I/O
SYNC_IN
I
I/O See Serial Interface Port Pin Description section for details.
I
I
Digital Power Supply. This pin is for I/O cells only, 3.3 V.
Input Signal Used to Synchronize Multiple AD9954s. This input is connected to the SYNC_CLK
output of a master AD9954.
45
46
SYNC_CLK
OSK
O
I
Clock Output Pin that Serves as a Synchronizer for External Hardware.
Input Pin Used to Control the Direction of the Shaped On-Off Keying Function When Programmed
for Operation. OSK is synchronous to the SYNC_CLK pin. When OSK is disabled, this pin should
be tied to DGND.
47, 48
<49>
PS0, PS1
AGND
I
I
Input Pins Used to Select One of the Internal Phase/Frequency Profiles. PS1 and PS0 are
synchronous to the SYNC_CLK pin. Change on these pins triggers a transfer of the contents of
the chosen internal buffer memory to the I/O registers (sends an internal I/O UPDATE).
The Exposed Paddle on the Bottom of the Package. It is a ground connection for the DAC and
must be attached to AGND in any board layout.
Rev. C | Page 9 of 40
AD9954
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
MKR1 101MHz
MKR1 160MHz
–61.55dB
REF 0dBm
REF 0dBm
ATTEN 10dB
–70.68dB
ATTEN 10dB
0
0
PEAK
LOG
10dB/
PEAK
LOG
10dB/
1R
1R
–10
–10
–20
–30
–20
–30
–40
MARKER
–40
MARKER
101MHz
160MHz
–70.68dB
–61.55dB
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
1
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
1
–100
–100
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
VBW 3kHz
VBW 3kHz
Figure 5. fOUT = 1 MHz, fCLK = 400 MSPS, WBSFDR
Figure 8. fOUT = 80 MHz, fCLK = 400 MSPS, WBSFDR
MKR1 90MHz
–69.12dB
MKR1 160MHz
–56.2dB
REF 0dBm
REF 0dBm
ATTEN 10dB
ATTEN 10dB
0
0
PEAK
LOG
PEAK
LOG
1R
1R
10dB/
10dB/
–10
–10
–20
–30
–20
–30
–40
MARKER
90MHz
–69.12dB
–40
MARKER
160MHz
–56.2dB
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
1
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
1
–100
–100
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
VBW 3kHz
VBW 3kHz
Figure 6. fOUT = 10 MHz, fCLK = 400 MSPS, WBSFDR
Figure 9 fOUT = 120 MHz, fCLK = 400 MSPS, WBSFDR
MKR1 80MHz
–68.44dB
MKR1 80MHz
–53.17dB
REF 0dBm
REF 0dBm
ATTEN 10dB
1R
ATTEN 10dB
0
0
PEAK
LOG
PEAK
LOG
1R
10dB/
10dB/
–10
–10
–20
–30
–20
–30
–40
MARKER
80MHz
–40
MARKER
80MHz
–68.44dB
–53.17dB
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
1
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
1
–100
–100
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
CENTER 100MHz
#RES BW 3kHz
SPAN 200MHz
SWEEP 55.56 s (401 PTS)
VBW 3kHz
VBW 3kHz
Figure 7. fOUT = 40 MHz, fCLK = 400 MSPS, WBSFDR
Figure 10. fOUT = 160 MHz, fCLK = 400 MSPS, WBSFDR
Rev. C | Page 10 of 40
Data Sheet
AD9954
MKR1 1.105MHz
–5.679dBm
MKR1 80.301MHz
REF –4dBm
REF –4dBm
ATTEN 10dB
ATTEN 10dB
–6.318dBm
1
1
0
0
PEAK
LOG
PEAK
LOG
10dB/
10dB/
–10
–10
–20
–30
–20
–30
–40
MARKER
1.105000MHz
–5.679dBm
–40
MARKER
80.301000MHz
–6.318dBm
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
ST
–100
ST
–100
CENTER 1.105MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
CENTER 80.25MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
VBW 30Hz
VBW 30Hz
Figure 11. fOUT = 1.1 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
Figure 14. fOUT = 80.3 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
MKR1 10MHz
MKR1 120.205MHz
REF 0dBm
REF –4dBm
ATTEN 10dB
–93.01dB
ATTEN 10dB
–6.825dBm
1
0
0
PEAK
LOG
10dB/
PEAK
LOG
10dB/
1R
–10
–10
–20
–30
–20
–30
–40
MARKER
–40
MARKER
120.205000MHz
–6.825dBm
10MHz
–93.01dB
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
1
ST
–100
–100
CENTER 10MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
CENTER 120.2MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
VBW 30Hz
VBW 30Hz
Figure 12. fOUT = 9.5 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
Figure 15. fOUT = 120.2 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
MKR1 39.905MHz
MKR1 600kHz
REF 0dBm
REF –4dBm
ATTEN 10dB
–5.347dBm
ATTEN 10dB
–0.911dB
1
1
0
0
PEAK
LOG
PEAK
LOG
10dB/
10dB/
–10
–10
–20
–30
–20
–30
–40
MARKER
39.905000MHz
–5.347dBm
–40
CENTER
160.5000000MHz
–50
–60
–70
–80
–90
–50
–60
–70
–80
–90
W1 S2
S3 FC
AA
W1 S2
S3 FC
AA
ST
–100
–100
CENTER 39.9MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
CENTER 160.5MHz
#RES BW 30Hz
SPAN 2MHz
SWEEP 199.2 s (401 PTS)
VBW 30Hz
VBW 30Hz
Figure 13. fOUT = 39.9 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
Figure 16. fOUT = 160 MHz, fCLK = 400 MSPS, NBSFDR, 1 MHz
Rev. C | Page 11 of 40
AD9954
Data Sheet
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
FALL (R1) = 396.4PS
RISE(R2) = 464.3PS
R1
R2
–120
–130
–140
–150
–160
–170
REF2 200mV 500ns M 500PS 20.0GS/S IT 10.0PS/PT –100PS
10
100
1k
10k
100k
1M
10M
A CH1
708mV
f (Hz)
Figure 19. Comparator Rise and Fall Time at 160 MHz
Figure 17. Residual Phase Noise with fOUT = 159.5 MHz,
f
CLK = 400 MSPS; PLL Bypassed (Green), PLL Set to 4× (Red), and
PLL Set to 20× (Blue)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–140
–150
–160
–170
10
100
1k
10k
100k
1M
f (Hz)
Figure 18. Residual Phase Noise with fOUT = 9.5 MHz, fCLK = 400 MSPS;
PLL Bypassed (Green), PLL Set to 4× (Red), and PLL Set to 20× (Blue)
Rev. C | Page 12 of 40
Data Sheet
AD9954
THEORY OF OPERATION
COMPONENT BLOCKS
REFCLK Input
The PLL is bypassed by programming a value outside the range
of 4 to 20 (decimal). When bypassed, the PLL is shut down to
conserve power.
The AD9954 supports several methods for generating the
internal system clock. An on-chip oscillator circuit is available
for initiating the low frequency reference signal by connecting a
crystal to the clock input pins. The system clock can be generated
using an internal, PLL-based reference clock multiplier, allowing
the part to operate with a low frequency clock source while still
providing a high sample rate for the DDS and DAC. For best
phase noise performance, a clean, stable clock with a high slew
rate should be used to drive the REFCLK pin and bypass the
multiplier.
The VCO in the PLL has a selectable frequency range. Use the
VCO
range bit (CFR2<2>) to set the appropriate range.
The PLL in the clock multiplier has a loop filter comprised
of on-chip components as well as external components.
Recommended values for the external resistor/capacitor
are provided in Table 4.
Table 4. External Loop Filter Components for Clock Multiplier
Multiply Value
Resistor Value
Capacitor Value (µF)
The available modes are configured using the CLKMODESELECT
pin, CFR1<4> and CFR2<7:3>. Note that the CLKMODESELECT
pin is a 1.8 V logic only and does not apply to 3.3 V logic.
Pulling CLKMODESELECT high enables the on-chip crystal
oscillator circuit. With the on-chip oscillator enabled, users of
the AD9954 connect an external crystal to the REFCLK and
4×
10×
20×
0 Ω
1 kΩ
243 Ω
0.1
0.1
0.01
DAC Output
inputs to produce a low frequency reference clock (see
REFCLK
Unlike many DACs, the DAC output on the AD9954 is referenced
to AVDD, not AGND.
Table 1 for the crystal frequency range supported). The signal
generated by the oscillator is buffered, and then delivered to the
rest of the chip. This buffered signal is provided on the
CRYSTAL OUT pin.
Two complementary outputs provide a combined full-scale
output current (IOUT). Differential outputs reduce the amount of
common-mode noise that may be present at the DAC output,
resulting in a better signal-to-noise ratio. The full-scale current
is controlled by means of an external resistor (RSET) connected
between the DAC_RSET pin and the DAC ground pin (Pin 49,
the exposed paddle). The full-scale current is proportional to
the resistor value by the equation
When the internal oscillator is disabled, an external oscillator
must provide the REFCLK and/or
signals. For differential
REFCLK
operation, these pins are driven with complementary signals. For
single-ended operation, a 0.1 µF capacitor should be connected
between the unused pin and the analog power supply. With the
capacitor in place, the clock input pin bias voltage is 1.35 V.
Table 5 summarizes the clock modes of operation. Note the PLL
multiplier is controlled via the CFR2<7:3> bits, independent of
the CFR1<4> bit.
RSET
=
(
39.19/IOUT Ω
)
The maximum full-scale output current of the combined
DAC outputs is 15 mA. Limiting the output to 10 mA
maximum provides the best spurious-free dynamic range
(SFDR) performance. The DAC output compliance range is
AVDD + 0.5 V to AVDD − 0.5 V. Voltages developed beyond
this range result in excessive DAC distortion and could potentially
damage the DAC output circuitry. Proper attention should be
paid to the load termination to keep the output voltage within
this compliance range.
Clock Multiplier
An on-board PLL allows multiplication of the REFCLK
frequency. The multiplication factor is set using CFR2<7:3>.
When programmed for values ranging from 0x04 to 0x14
(decimal 4 to 20), the PLL multiplies the REFCLK input
frequency by the programmed value. The user must consider the
specified maximum frequency for the PLL when programming. If
the multiplication factor is changed, the user must allocate time
to allow the PLL to lock (approximately 1 ms).
Table 5. Clock Input Modes of Operation
CFR1<4>
CLKMODESELECT
CFR2<7:3>
4 ≤ M ≤ 20
M < 4 or M > 20
4 ≤ M ≤ 20
M < 4 or M > 20
X
Oscillator Enabled?
System Clock
fCLK = fOSC × M
fCLK = fOSC
fCLK = fOSC × M
fCLK = fOSC
Frequency Range (MHz)
80 < fCLK < 400
20 < fCLK < 30
80 < fCLK < 400
10 < fCLK < 400
N/A
Low
Low
Low
Low
High
High
Low
Low
X
Yes
Yes
No
No
No
High
fCLK = 0
Rev. C | Page 13 of 40
AD9954
Data Sheet
Comparator
that are fed to the DDS core as the seed value for the phase
accumulator: a frequency accumulator, the static RAM, and
the registers of the control logic.
Some applications (for example, clocking) prefer a square-wave
signal rather than a sine wave. In support of such applications,
the AD9954 includes an on-chip comparator. The comparator
has a bandwidth greater than 200 MHz and a common-mode
input range of 1.3 V to 1.8 V. The comparator can be turned off
to reduce power consumption using the comparator power-
down bit, CFR1<6>.
For applications where a static output frequency or more than
four predefined output frequencies need to be switched between,
in some variable or undefined order, the primary method of
setting the FTW is by programming the desired value into the
FTW0 register.
Frequency Accumulator
For applications where up to four specific sets of FTWs, or pre-
defined series of FTWs are needed, the on-board RAM can be
programmed with the desired FTWs, and the profile pins can
be used to toggle between those sets/series.
This block is used for linear sweep mode; transitioning from
the start frequency (F0) to the terminal frequency (F1) is not
instantaneous but instead is implemented in a swept or ramped
fashion. This frequency ramping is accomplished by stepping
through intermediate frequencies between F0 and F1.
For applications where a steady sweeping of frequency is
desired, a second frequency accumulator is provided. The seed
value and minimum/maximum numbers for the frequency
accumulator are user programmable, although certain rules
must be followed to avoid overflowing that accumulator.
The linear sweep block uses the falling and rising delta
frequency tuning words, the falling and rising delta frequency
ramp rates, and the frequency accumulator. The Linear Sweep
Enable Bit CFR1<21> enables the linear sweep block. The linear
sweep no dwell bit establishes the action to be performed upon
reaching the terminal frequency in a sweep. See the Modes of
Operation section for more details.
Phase Offset Word Mux
As shown in Figure 2, there are two sources for the POW that
are fed to the DDS core as an adder to the output of the phase
accumulator: the static RAM and the registers of the control
logic. Using this feature enables synchronization of the DDS
output to other system signals as well as phase modulation.
DDS Core
The output frequency (fO) of the DDS is a function of the
frequency of system clock (SYSCLK), the value of the frequency
tuning word (FTW), and the capacity of the phase accumulator
(232, in this case). The exact relationship is given below with fs
defined as the frequency of SYSCLK.
For applications where a static output phase or more than four
predefined output phases need to be switched between, in some
variable or undefined order, the primary method of setting the
POW is by programming the desired value into the POW0
register.
fO = (FTW)(fS)/232 with 0 ≤ FTW ≤ 231
fO = fS × (1 − (FTW/232)) with 231 < FTW < 232 − 1
For applications where up to four specific sets of POWs, or
predefined series of POWs are needed, the on-board RAM can
be programmed with the desired POWs, and the profile pins
can be used to toggle between those sets/series.
Each system clock cycle, the FTW is added to the value
previously held in the phase accumulator. The value at the
output of the phase accumulator is then summed with a user-
defined, 14-bit phase offset value (POW). The most significant
19 bits of that summation are then translated to an amplitude
value via the cos(x) functional block. Truncation of the LSBs is
implemented to reduce the power consumption of the DDS
core. This truncation does not reduce frequency resolution.
The phase offset formula is
POW
214
Φ =
×360°
A digital delay block exists in the phase offset programming
path to ensure matched latency with changes to the frequency
tuning word. This enables users to easily program the device to
change from one combined phase/frequency combination to
another smoothly and seamlessly.
In certain applications, it is desirable to have the ability to force
the output signal to zero phase. Simply setting the FTW to 0
does not accomplish this; it only stalls the core at its current
phase value. A control bit is provided to force the phase
accumulator output to zero.
Continuous and Clear-and-Release Frequency and Phase
Accumulator Clear Functions
At power-up, the clear phase accumulator bit is set to Logic 1,
but the buffer memory for this bit is cleared (Logic 0). Therefore,
upon power-up, the phase accumulator remains clear until the
first I/O UPDATE is issued. I/O UPDATE transfers data from
the input buffers to the active control registers. See the
Functionality of the SYNC_CLK and I/O UPDATE section
for more details.
The AD9954 allows for a continuous zeroing of the frequency
sweep logic and the phase accumulator as well as a clear and
release or automatic zeroing function. The auto clear bits are
CFR1<14:13>. The continuous clear bits are CFR1<11:10>.
Frequency Tuning Word Mux
As shown in Figure 2, there are three sources for the FTW
Rev. C | Page 14 of 40
Data Sheet
AD9954
contents of the amplitude scale factor register, allowing the user
to ramp to a value less than full scale.
Clear-and-Release Function
When set for auto clearing, the corresponding accumulator is
cleared and then begins to accumulate again upon receipt of an
I/O update or change on one of the profile pins. This is repeated
for every subsequent I/O update or change on one of the profile
pins until the appropriate autoclear control bit is cleared. It is
perfectly valid to have one accumulator set to autoclearing and
the other set to continuous clear.
Table 6. Autoscale Factor Internal Step Size
ASF<15:14> (Binary)
Increment/Decrement Size
00
01
10
11
1
2
4
8
Amplitude Control Options
OSK Ramp Rate Timer
Shaped On-Off Keying
The OSK ramp rate timer is a loadable down counter, which
generates the clock signal to the 14-bit counter that generates
the internal scale factor. The ramp rate timer is loaded with
the value of the autoscale factor register (ASFR) every time
the counter reaches 1 (decimal). This load and countdown
operation continues for as long as the timer is enabled, unless
the timer is forced to load before reaching a count of 1.
The shaped on-off keying function is enabled/disabled using
the OSK enable bit (CFR1<25>). This function allows the
user to control the ramp-up and ramp-down time when turning
the DAC on or off. This function is primarily used in burst
transmissions of digital data to reduce the adverse spectral
impact of short, abrupt bursts of data.
Both auto and manual shaped on-off keying modes are
supported. CFR1<24> is used to select between auto and
manual on-off keying modes. Figure 20 shows the block
diagram of the OSK circuitry.
If the load ARR control bit (CFR1<26>) is set, the ramp rate
timer is loaded upon an I/O update, upon a change in profile
input, or upon reaching a value of 1. The ramp timer can be
loaded before reaching a count of 1 by three methods.
Autoshaped On-Off Keying Mode Operation
The first method is by toggling the OSK pin or sending a rising
edge to the I/O UPDATE pin (or changing the state of a profile
pin). For this method, the ASFR value is loaded into the ramp
rate timer, which then proceeds to count down as normal.
When autoshaped on-off keying mode is enabled, a single-scale
factor is internally generated and applied to the multiplier input
for scaling the output of the DDS core block (see Figure 20). The
scale factor is the output of a 14-bit counter that increments/
decrements at a rate determined by the contents of the 8-bit
output ramp rate register. The scale factor increments if the
OSK pin is high and decrements if the OSK pin is low. The scale
factor is an unsigned value; all 0s multiply the DDS core output
by 0 (decimal), and 0x3FFF multiplies the DDS core output by
16,383 (decimal).
The second method is if the load ARR control bit (CFR1<26>)
is set and an I/O update (or change in profile) is issued.
The last method is by setting the sweep enable bit. This switches
from inactive autoshaped on-off keying mode to the active
autoshaped on-off keying mode.
Manual Shaped On-Off Keying Mode Operation
Table 6 details the increment/decrement step size of the
internally generated scale factor per the ASF<15:14> bits.
When configured for manual shaped on-off keying, the
content of the ASFR sets the scale factor for the data path
Note that the maximum amplitude allowed is limited by the
DDS CORE
AUTO OSK
ENABLE
CFR1<24>
TO DAC
COS(X)
OSK ENABLE
CFR<25>
SYNC_CLK
LOAD OSK TIMER
CFR1<26>
0
1
OSK PIN
AMPLITUDE RAMP
RATE REGISTER
(ASF)
AMPLITUDE SCALE
FACTOR REGISTER
(ASF)
0
HOLD
UP/DN
OUT
LOAD DATA
EN
INC/DEC ENABLE
CLOCK
RAMP RATE TIMER
AUTOSCALE
FACTOR GENERATOR
Figure 20. On-Off Shaped Keying, Block Diagram
Rev. C | Page 15 of 40
AD9954
Data Sheet
To perform 4-tone shift keying, the user programs each RAM
segment control word for direct switch mode and a unique
beginning address value. Program the RAM enable and RAM
destination bits (CFR1<31:30>) to enable the RAM and direct
the RAM output to be the FTW (FSK) or the POW (PSK). The
PS1 and PS0 inputs are the 4-tone FSK/PSK data inputs. When
the profile is changed, the data stored at the new profile is
loaded into either the phase accumulator (FSK) or the phase
offset adder (PSK). When set for PSK, Bits<17:0> of the RAM
output are unused when the RAM destination bit is set. Two-
tone shift keying only uses one profile pin.
MODES OF OPERATION
Single-Tone Mode
In single-tone mode, the DDS core uses a static tuning word.
Whatever value is stored in FTW0 is supplied to the phase
accumulator. This value can only be changed manually by
writing a new value to FTW0 and then by issuing an I/O update.
Phase adjustments are made using the phase offset register.
RAM-Controlled Modes of Operation
Three important points apply to the RAM-controlled modes:
•
The user must ensure that the beginning address is lower
than the final address.
Ramp-Up Mode
•
Changing profiles or issuing an I/O update automatically
terminates the current sweep and starts the next sweep, unless
otherwise stated.
Setting the RAM destination bit true such that the RAM
output drives the phase offset adder is valid. While the
sections that follow describe frequency sweeps, phase
sweep operation is also available. The RAM destination bit
(CFR1<30>) controls whether the RAM output drives the
phase accumulator (frequency) or the phase offset adder
(phase).
Ramp-up mode, in conjunction with the segmented RAM
capability, allows up to four different sweep profiles to be
programmed into the AD9954. The AD9954 is programmed
for ramp-up mode by enabling the RAM using the RAM enable
bit (CFR1<31>) and programming the RAM mode control bits
of each profile to be used to 001(b).
•
When a sweep is initiated (via an I/O update or change in
profile bits), the RAM address generator loads the RAM
segment beginning address bits of the current RSCW, driving
the RAM output from this address, and the ramp rate timer
loads the RAM segment address ramp rate bits. When the ramp
rate timer finishes a cycle, the RAM address generator increments
to the next address, the timer reloads the ramp rate bits and
begins a new countdown cycle. This sequence continues until
the RAM address generator has incremented to an address
equal to the RAM segment final address bits of the current
RSCW. At this point, the next state is dependent upon whether
no-dwell mode is active. See the no-dwell bit (CFR1<2>) in the
register maps (see Table 12 and Table 13).
The AD9954 offers five modes of RAM-controlled operation
(see Table 7).
Table 7. RAM Modes of Operation
RSCW<7:5> (Binary) Mode
Notes
000
001
010
Direct Switch No sweeping, profiles
valid, no dwell ignored
Ramp Up
Sweeping, profiles valid,
no-dwell valid
Bidirectional Sweeping, PS0 is a
In this mode, asymmetrical FSK modulation can be implemented
by configuring the RAM for two segments, and using the PS0
pin as the data input.
Ramp
direction control pin,
no-dwell ignored
Sweeping, profiles valid,
011
Continuous
Bidirectional no-dwell ignored
Ramp
Bidirectional Ramp Mode
100
Continuous
Recirculation no-dwell ignored
Invalid mode Default to direct switch
Sweeping, profiles valid,
Bidirectional ramp mode allows the AD9954 to offer a
symmetrical sweep between two frequencies using the PS0
signal as the control input. The AD9954 is programmed for
bidirectional ramp mode using the RAM enable bit (CFR1<31>)
and programming the RAM segment mode control bits of each
desired profile to 010(b). PS1 input is ignored; the PS0 input is
the ramp direction indicator. The memory is not segmented,
using only one beginning and one final address. The address
registers for controlling RAM are located in the RAM segment
control word (RSCW) associated with Profile 0.
101, 110, 111
Direct Switch Mode
Direct switch mode enables frequency shift keying (FSK) or
phase shift keying (PSK) modulation. The AD9954 is
programmed for direct switch using the RAM enable bit
(CFR1<31>) and programming the RAM segment mode
control bits of each desired profile to 000(b). This mode simply
reads the RAM contents at the RAM segment beginning
address for the current profile. No address ramping occurs in
this mode.
Rev. C | Page 16 of 40
Data Sheet
AD9954
Upon entering this mode (via an I/O update or changing the
PS0 pin), the RAM address generator loads the RAM segment
beginning address bits of RSCW0 and the ramp rate timer loads
the RAM segment address ramp rate bits. The RAM drives data
from the beginning address, and the ramp rate timer begins
counting down to 1. When the timer reaches zero, the RAM
address is incremented if PS0 is high and decrements if PS0 is
low. Toggling the PS0 pin does not cause the device to generate
an internal I/O update; transfers of data from the I/O buffers to
the internal registers are only initiated by a rising edge on the
I/O UPDATE pin.
Continuous Recirculation Mode
Continuous recirculation mode allows the AD9954 to offer
an automatic, continuous unidirectional sweep between two
frequencies. The AD9954 is programmed for continuous
recirculation mode using the RAM enable bit (CFR1<31>)
and programming the RAM segment mode control bits of
each desired profile to 100(b).
Upon entering this mode (via an I/O update or changing Pin
PS1 or Pin PS0), the RAM address generator loads the RAM
segment beginning address bits of the current RSCW and the
ramp rate timer loads the RAM segment address ramp rate bits.
The RAM drives data from the beginning address, and the ramp
rate timer begins to count down to 1. When the ramp rate timer
completes a cycle, the RAM address generator increments to the
next address, and the timer reloads the ramp rate bits and
continues counting down. This sequence continues until the
RAM address generator has incremented to an address equal to
the RAM segment final address bits of the current RSCW. Upon
reaching this terminal address, the RAM address generator
reloads the RAM segment beginning address bits and the
sequence repeats until a new mode is selected.
RAM address control is now a function of the PS0 input. When
polarity of the PS0 bit is changed, the RAM address generator
increments/decrements to the next address and the ramp rate
timer is reloaded. As in the ramp-up mode, this sequence
continues until the RAM address generator has incremented/
decremented to an address equal to the final/beginning address
as long as the PS0 input remains high/low. Once the final/
beginning address is reached, the sweep stalls until the polarity
on PS0 is changed.
All data in the RAM segment control words associated with
Profile 1, Profile 2, and Profile 3 are ignored. Only the information
in the RAM segment control word for Profile 0 is used to
control the RAM.
Internal Profile Control
The AD9954 offers a mode in which a composite frequency sweep
can be built with software-programmable timing control. Internal
profile control capability disengages the PS1 pin and the PS0 pin
and enables the AD9954 to take control of switching between
profiles. Modes are defined that allow continuous or single-burst
profile switches for three combinations of profile selection bits
(see Table 8). Internal profile control mode is engaged using Bits
CFR1<29:27> per Table 8 Internal profile control is only valid
when the device is operating in RAM mode. There is no internal
profile control for linear sweeping operations.
Continuous Bidirectional Ramp Mode
Continuous bidirectional ramp mode allows the AD9954
to offer an automatic, symmetrical sweep between two
frequencies. The AD9954 is programmed for continuous
bidirectional ramp mode using the RAM enable bit (CFR1<31>)
and programming the RAM segment mode control bits of each
desired profile to 011(b). In general, this mode is identical in
control to the bidirectional ramp mode, except the ramp up and
down is automatic (no external control via the PS0 input), and
switching profiles are valid. This mode enables generation of an
automatic saw tooth sweep characteristic.
When the internal profile control mode is engaged, the RAM
segment mode control bits are ignored; the device operates all
profiles in ramp-up mode. Switching between profiles occurs
when the RAM address generator has exhausted the memory
contents for the current profile.
Upon entering this mode (via an I/O update or changing the
PS1 or PS0 pins), the RAM address generator loads the RAM
segment beginning address bits of the current RSCW and the
ramp rate timer loads the RAM segment address ramp rate bits.
The RAM drives data from the beginning address, and the ramp
rate timer begins counting down to 1. When the ramp rate timer
completes the countdown, the RAM address generator increments
to the next address, and the timer reloads the ramp rate bits and
continues counting down. This continues until the RAM address
generator has incremented to an address equal to the RAM
segment final address bits of the current RSCW. Upon reaching
this final address, the RAM address generator begins
decrementing each time the ramp rate timer completes a
countdown cycle until it reaches the RAM segment beginning
address. Upon reaching the beginning address, the entire
sequence repeats until a new mode is selected.
Rev. C | Page 17 of 40
AD9954
Data Sheet
Table 8. Internal Profile Control
ramps from FTW0 to FTW1 and the RSRR register is loaded
into the sweep rate timer. When the timer counts down to one,
the frequency accumulator cycles once, increasing by the seed
value. This accumulation of the RDFTW at the rate given by the
ramp rate (RSRR) continues until the output of the frequency
adder is equal to the FTW1 register value, or PS0 is pulled low.
CFR1<29:27>
(Binary)
Mode Description
000
Internal control inactive
001
Internal control active, single-burst, activate
Profile 0, then Profile 1, then stop
010
011
Internal control active, single-burst, activate
Profile 0, then Profile 1, then Profile 2, then stop
Internal control active, single-burst, activate
Profile 0, then Profile 1, then Profile 2, then
Profile 3, then stop
When PS0 is low, the 32-bit falling delta frequency tuning word
(FDFTW) is the seed value for the frequency accumulator, it
ramps down from FTW1 to FTW0 and the FSRR register is
loaded into the sweep rate timer. When the timer counts down
to one, the frequency accumulator cycles once, decreasing by
the seed value. This accumulation of the FDFTW at the rate
given by the ramp rate (FSRR) continues until the output of the
frequency adder is equal to the FTW0 register value, or PS0 is
pulled high.
100
101
Internal control active, continuous, activate
Profile 0, then Profile 1, then Loop Starting 0
Internal control active, continuous, activate
Profile 0, then Profile 1, then Profile 2, then
Loop Starting 0
110
111
Internal control active, continuous, activate
Profile 0, then Profile 1, then Profile 2, then
Profile 3, and then Loop Starting 0
Pin PS0 controls the direction of the sweep, rising to FTW1 or
falling to FTW0. Upon reaching the destination frequency, the
AD9954 linear sweep function either holds at the destination
frequency until the state on PS0 is changed or immediately
returns to the initial frequency, FTW0, depending on the state
of the Linear Sweep No-Dwell Bit CFR1<02>. While operating
in linear sweep mode, toggling PS0 does not cause the device to
generate an internal I/O update. When PS0 is acting as the
sweep direction indicator, any transfer of data from the I/O
buffers to the internal registers can only be initiated by a rising
edge on the I/O UPDATE pin.
Invalid
A single-burst mode is one in which the composite sweep is
executed once. For example, assume the device is programmed
for ramp-up mode and the CFR1<29:27> bits are written to
Logic 010(b). Upon receiving an I/O update, the internal
control logic signals the device to begin executing the ramp-up
mode sequence for Profile 0. Upon reaching the RAM segment
final address value for Profile 0, the device jumps to the beginning
address of Profile 1 and begins executing that ramp-up sequence.
Upon reaching the RAM segment final address value for
Profile 1, the device jumps to the beginning address of Profile 2
and begins executing that ramp-up sequence. When the RAM
segment final address value for Profile 2 is reached, the
sequence is over and the composite sweep has completed.
Issuing another I/O update restarts the burst process.
The linear sweep function of the AD9954 requires the lowest
frequency to be loaded into the FTW0 register and the highest
frequency into the FTW1 register. For piece-wise, nonlinear
frequency transitions, it is necessary to reprogram the registers
while the frequency transition is in process.
After a reset, the device is initially in single-tone mode. The
programming steps to operate in linear sweep mode are:
A continuous internal profile control mode is one in which the
composite sweep is continuously executed for as long as the
device is programmed into that mode. Using the previous
example, except programming the CFR1<29:27> bits to
Logic 101(b), the operation would be identical until the RAM
segment final address value for Profile 2 is reached. At this
point, instead of stopping the sequence, the device jumps back
to the beginning address of Profile 0 and continues sweeping.
1. PS1:0 = 00.
2. Set the linear sweep enable bit (CFR1<21>) and set or clear
the linear sweep no-dwell bit (CFR1<2>) as desired.
3. Program the rising and falling delta frequency tuning
words and ramp rate values.
4. Program the lower and higher output frequencies into the
FTW0 and FTW1 registers, respectively.
5. Apply an I/O update to move this data into the registers
(the instantaneous output frequency is FTW0).
6. Change the PS0 input as desired to sweep between the
lower to higher frequency and back.
Linear Sweep Mode
The AD9954 is placed in linear sweep mode using the Linear
Sweep Enable Bit CR1<21>. PS1 must be tied low. When in
linear sweep mode, the AD9954 output frequency ramps up
from a starting frequency, programmed by FTW0 to a finishing
frequency FTW1, or down from FTW1 to FTW0. The delta
frequency tuning words and the ramp rate word determine the
rate of this ramping. The Linear Sweep No-Dwell Bit CFR1<2>
controls the behavior of the device upon reaching the final
frequency.
Figure 21 depicts a typical frequency ramping operation. The
device initially powers up in single-tone mode. The profile
inputs are low, setting FTW0 as the seed value for the phase
accumulator. The user then writes to the linear sweep enable bit,
the rising and falling delta frequency tuning words, and ramp
rates via the serial port (Point A in Figure 21. In this example, the
linear sweep no-dwell bit is cleared (CFR1<2>).
When PS0 is high, the 32-bit rising delta frequency tuning word
(RDFTW) is the seed value for the frequency accumulator, it
Rev. C | Page 18 of 40
Data Sheet
AD9954
fOUT
B
FTW1
A
FTW0
TIME
SINGLE-TONE
MODE
LINEAR SWEEP MODE
PS<0> = 1
PS<0> = 0
PS<0> = 0
AT POINT A: LOAD RISING RAMP RATE REGISTER, APPLY RISING DFTW.
AT POINT B: LOAD FALLING RAMP RATE REGISTER, APPLY FALLING DFTW.
Figure 21. Linear Sweep Frequency Plan
fOUT
B
B
B
FTW1
A
A
A
FTW0
TIME
SINGLE-TONE
MODE
PS<0> = 0
PS<0> = 1 PS<0> = 0 PS<0> = 1
PS<0> = 0
PS<0> = 1
LINEAR SWEEP MODE ENABLE–NO DWELL BIT SET
Figure 22. Linear Sweep Using No-Dwell Frequency Plan
Linear Sweep No-Dwell Feature
Resetting the Ramp Rate Timer
See CFR1<2> in the register maps (see Table 12 and Table 13)
for general details of the no-dwell mode. Figure 22 depicts the
linear sweep mode operation when the linear sweep no-dwell
bit is set. The Label A points indicate where a rising edge on
PS0 is detected; the Label B points indicate where the AD9954
has determined fOUT has reached the terminal frequency and
automatically returns to the starting frequency. Note that in this
mode, only sweeps from FTW0 to FTW1 using the positive
linear sweep control word are supported. Toggling PS0 from 1
to 0 neither initiates a falling sweep when the no-dwell bit is set,
nor interrupts a positive sweep already underway.
The ramp timer can be reset before reaching a count of 1 by
three methods.
Method one is by changing the PS0 input pin. When the PS0
input pin toggles from 0 to 1, the RSRRW value is loaded into
the ramp rate timer, which then proceeds to countdown as
normal. When the PS0 input pin toggles from 0 to 1, the falling
sweep ramp rate word (FSRRW) value is loaded into the ramp
rate timer, which then proceeds to countdown as normal.
The second method uses the LOAD SRR @ I/O UD bit
(CFR1<15>), see Table 12 for details.
Rev. C | Page 19 of 40
AD9954
Data Sheet
The last method in which the sweep ramp rate timer can be
reset is changing from inactive linear sweep mode to active
linear sweep mode using the linear sweep enable bit (CFR1<21>).
the digital logic (CFR1<7:4>). With the exception of CFR1<6>,
these bits are superseded when the externally controlled power-
down pin (PWRDWNCTL) is high. External power-down
control is supported on the AD9954 via the PWRDWNCTL
input pin. When the PWRDWNCTL input pin is high, the
AD9954 enters a power-down mode based on the CFR1<3> bit.
When the PWRDWNCTL input pin is low, it operates normally.
See CFR1<3> in Table 12 for details.
For methods two and three, the ramp rate timer loads a value
determined by the state of PS0 (0 = F SRRW, 1 = RSRRW).
Power-Down Functions of the AD9954
The AD9954 supports an externally controlled (or hardware)
power-down feature as well as software-programmable power-
down bits capable of individually powering down specific unused
circuit blocks.
Table 9 details the logic level for each power-down bit that
drives out of the AD9954 core logic to the analog section and
the digital clock generation section of the chip for the external
power-down operation.
Software-controlled power-down enables individual powering
down of the DAC, comparator, PLL, input clock circuitry, and
Table 9. Power-Down Control Functions
Control
Mode Active
Description
PWRDWNCTL = 0, CFR1<3> don’t care
Software control
Digital power-down = CFR1<7>
Comparator power-down = CFR1<6>
DAC power-down = CFR1<5>
Clock input power-down = CFR1<4>
PWRDWNCTL = 1, CFR1<3> = 0
PWRDWNCTL = 1, CFR1<3> = 1
External control, fast recovery
power-down mode
Digital power-down = 1’b1
Comparator power-down = 1’b0 or CFR1<6>
DAC power-down = 1’b0
Clock input power-down = 1’b0
Digital power-down = 1’b1
Comparator power-down = 1’b1
DAC power-down = 1’b1
External control, full power-down
mode
Clock input power-down = 1’b1
Rev. C | Page 20 of 40
Data Sheet
AD9954
The I/O update signal coupled with SYNC_CLK is used to
SYNCHRONIZATION—REGISTER UPDATES (I/O
UPDATE)
Functionality of the SYNC_CLK and I/O UPDATE
transfer internal buffer contents into the control registers. The
combination of the SYNC_CLK pin and the I/O UPDATE pin
provides the user with constant latency relative to SYSCLK and
ensures phase continuity of the analog output signal when a
new tuning word or phase offset value is asserted.
Data into the AD9954 is synchronous to the SYNC_CLK
signal (supplied externally to the user on the SYNC_CLK pin).
The I/O UPDATE pin is sampled on the rising edge of the
SYNC_CLK.
Figure 23 and Figure 24 demonstrate an I/O update timing
cycle and synchronization.
Internally, SYSCLK is fed to a divide-by-four frequency divider
to produce the SYNC_CLK signal. The SYNC_CLK signal is
made available to the system on the SYNC_CLK pin. This
enables synchronization of external hardware with the device’s
internal clocks. This is accomplished by providing the SYNC_CLK
signal as an output that external hardware can then use to
synchronize against.
Synchronization logic notes include the following:
•
•
The I/O update signal is edge detected to generate a single-
cycle clock signal that drives the register bank flops. The
I/O update signal has no constraints on duty cycle. The
minimum low time on I/O update is one SYNC_CLK clock
cycle.
The I/O UPDATE pin is set up and held around the rising
edge of SYNC_CLK. Setup and hold time specifications
can be found in Table 2.
SYNC_CLK
DISABLE
0
SYSCLK
÷4
OSK
PS<1:0>
I/O UPDATE
D
Q
D
D
Q
Q
EDGE
DETECTION
LOGIC
TO CORE LOGIC
SYNC_CLK
GATING
SCLK
SDIO
CS
REGISTER
MEMORY
I/O BUFFER
LATCHES
Figure 23. I/O Synchronization Block Diagram
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 24. I/O Synchronization Timing Diagram
Rev. C | Page 21 of 40
AD9954
Data Sheet
RAM
Synchronizing Multiple AD9954s
The AD9954 incorporates a block of SRAM. The RAM is a
bidirectional single port. Read and write operations cannot
occur simultaneously. Write operations to the serial I/O port
take precedence; therefore, if an attempt to write to RAM is
made during a read operation, the read operation is halted. The
RAM is configurable using the RAM Segment Control Word<7:5>
and data in the control function register.
There are three modes of synchronization available to the user:
an automatic synchronization mode, a software-controlled
manual synchronization mode, and a hardware-controlled
manual synchronization mode. The following requirements
apply to all modes. First, all units must share a common clock
source. Trace lengths and path impedance of the clock tree must
be designed to keep the phase delay of the different clock branches
as closely matched as possible. Second, the I/O update signal’s
rising edge must be provided synchronously to all devices being
synchronized. Finally, the DVDD_I/O supply should be set to
3.3 V for all devices that are to be synchronized. AVDD and
DVDD should be left at 1.8 V.
Using the RAM enable bit (CFR1<31>), the RAM output can be
enabled to drive the input to either the phase accumulator or
the phase offset adder; the RAM destination bit (CFR1<30>)
sets the routing. When the RAM output drives the phase
accumulator, the phase offset word (POW, Address 0x05) drives
the phase-offset adder. Conversely, when the RAM output
drives the phase-offset adder, the frequency tuning word (FTW,
Address 0x04) drives the phase accumulator. When CFR1<31>
disables the RAM, it is inactive unless being written to via the
serial port. The RAM is mapped into one of four profiles
determined by the PS1 and PS0 input pins. Note that these
profiles may overlap. For example, Profile 0 may use RAM
Address Location 0 to Address Location 12, and Profile 1 may use
RAM Address Location 5 to Address Location 20, and so forth.
In automatic synchronization mode, one device is chosen as a
master, the other device(s) is slaved to this master. All slaves
automatically synchronize their internal clocks to the SYNC_CLK
output signal of the master device. Use the automatic
synchronization bit (CFR1<23>) to configure each slave.
Connect the SYNC_IN input(s) to the master SYNC_CLK
output. Slave devices continuously update the phase relationship of
their SYNC_CLK until it is in phase with the SYNC_IN input.
The high speed sync enhancement enable bit (CFR2<11>) must
be programmed correctly.
All RAM write or read operations to/from the RAM are
controlled by the PS1 and PS0 input pins and the respective
RAM segment control word. To write to the RAM, a RAM
segment must be defined in a RAM segment control word. The
RAM segment that was defined must then be selected by use of
the profile select pins, PS0 and PS1. With the correct RAM
segment selected, the special instruction byte of 0xB0 should
be sent. When the instruction byte to write to the RAM is sent
to the part, the serial port controller immediately polls the
corresponding RAM segment control word. From this register,
the serial port controller makes note of the start address and the
stop address. It then calculates how many entries there are in
the segment, and how many bytes of data to expect. After
sending the special instruction byte of 0xB0, the user must send
all RAM entries for the currently selected profile to the part.
In software manual synchronization mode, the user can force
the device to advance the SYNC_CLK rising edge one SYSCLK
cycle (¼ SYNC_CLK period). Manual synchronization mode
is established using the slave device’s software manual
synchronization bit (CFR1<22>). See the bit description in
Table 12 for more details.
In hardware manual synchronization mode, the SYNC_IN
input pin is configured such that it now advances the rising edge
of the SYNC_CLK signal each time the device detects a rising edge
on the SYNC_IN pin. Hardware manual synchronization mode is
established using the hardware manual synchronization bit
(CFR2<10>). See the bit description in Table 12 for more details.
Using a Single Crystal to Drive Multiple AD9954 Clock
Inputs
For example, consider a case where RAM Segment 2 begins at
Address 21 and ends at Address 120. First, write to RAM Segment
Control Word 2 with a starting address of 21, with a stop address
of 120, and specify a ramp rate and a mode of operation. Next, set
PS1 to 1 and PS0 to 0 to select RAM Segment 2 and then send
the instruction byte of 0xB0. The part is now ready to put the first
32-bit word into the RAM at Address 21, to expect 100 32-bit
words, and to store the last one at Address 120. It automatically
controls sending the data from the serial port to the correct RAM
address. Therefore, precede sending 100 32-bit words of data to
the part. After the 3200th SCLK cycle, the write operation is
complete, and all 100 words are stored in the RAM, from
Address 21 to Address 120.
The AD9954 crystal oscillator output signal is available on the
CRYSTAL OUT pin, enabling one crystal to drive multiple
AD9954s. To drive multiple AD9954s with one crystal, the
CRYSTAL OUT pin of the AD9954 using the external crystal
should be connected to the REFCLK input of the other AD9954.
The CRYSTAL OUT pin must be enabled using the CRYSTAL
OUT Pin Active Bit CFR2<9>. The drive strength of the
CRYSTAL OUT pin is fairly low; therefore, the signal
should be buffered if multiple loads are being driven.
Data Sheet
AD9954
Serial I/O Port
There are two phases to a communication cycle with the
AD9954. Phase 1 is the instruction cycle, which is the writing of
an instruction byte into the AD9954, coincident with the first
eight SCLK rising edges. The instruction byte provides the
AD9954 serial port controller with information regarding
Phase 2, the data transfer cycle. The instruction byte defines
whether the upcoming data transfer is a read or a write and the
serial address of the register being accessed.
The AD9954 serial port is a flexible, synchronous, serial
communications port that easily interfaces to many industry-
standard microcontrollers and microprocessors. The serial I/O port
is compatible with most synchronous transfer formats, including
both the Motorola 6905/11 SPI® and Intel® 8051 SSR protocols.
The interface accesses all registers that configure the AD9954. MSB
first and LSB first transfer formats are supported. In addition, the
AD9954’s serial interface port can be configured as a single pin I/O
(SDIO), which allows a 2-wire interface, or two unidirectional pins
for in/out (SDIO/SDO), which enables a 3-wire interface. Two
The first eight SCLK rising edges of each communication cycle
are used to write the instruction byte into the AD9954. The
remaining SCLK edges are for Phase 2 of the communication
cycle. Phase 2 is the actual data transfer between the AD9954
and the system controller. The number of bytes transferred
during Phase 2 of the communication cycle is a function of the
register being accessed. For example, when accessing the Control
Function Register 2, which is three bytes wide, Phase 2 requires that
three bytes be transferred. If accessing the frequency tuning word,
which is four bytes wide, four bytes must be transferred. After
transferring all data bytes per the instruction byte, the
communication cycle is complete.
optional pins, IOSYNC and , provide further flexibility for
CS
system design with the AD9954.
SERIAL PORT OPERATION
With the AD9954, the instruction byte specifies read/write
operation and register address. Serial operations on the AD9954
only occur at the register level, they do not occur on the byte
level. For the AD9954, the serial port controller recognizes the
instruction byte register address and automatically generates the
proper register byte address. In addition, the controller expects
to access all bytes of that register. It is a requirement that all
bytes of a register be accessed during serial I/O operations, with
one exception; the IOSYNC function can be used to abort an
I/O operation, thereby allowing less than all bytes to be
accessed.
At the completion of any communication cycle, the AD9954
serial port controller expects the next eight rising SCLK edges
to be the instruction byte of the next communication cycle. All
data input to the AD9954 is registered on the rising edge of
SCLK. All data is driven out of the AD9954 on the falling edge
of SCLK. Figure 25 through Figure 28 are provided to aid in
understanding the general operation of the AD9954 serial port.
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 25. Serial Port Write Timing–Clock Stall Low
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
SCLK
I
I
I
I
I
I
I
I
0
DON'T CARE
SDIO
SDO
7
6
5
4
3
2
1
D
D
D
D
D
D
D
D
O 0
O 7
O 6
O 5
O 4
O 3
O 2
O 1
Figure 26. 3-Wire Serial Port Read Timing–Clock Stall Low
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
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 27. Serial Port Write Timing–Clock Stall High
Rev. C | Page 23 of 40
AD9954
Data Sheet
INSTRUCTION CYCLE
DATA TRANSFER CYCLE
CS
SCLK
I
I
I
I
I
I
I
I
D
D
D
D
D
D
D
D
O 1 O 0
SDIO
7
6
5
4
3
2
1
0
O 7
O 6
O 5
O 4
O 3
O 2
Figure 28. 2-Wire Serial Port Read Timing—Clock Stall High
the register at this memory location and notes that the ASF is
2 bytes wide. The serial port controller’s state machines sets to
16 and awaits 16 rising edges on the SCLK and 16 bits of data
on the SDIO line. Send 16 rising edges on SCLK, and the binary
data 10000000 00000000 on the SDIO line.
SERIAL INTERFACE PORT PIN DESCRIPTIONS
SCLK—Serial Clock. The serial clock pin is used to synchronize
data to and from the AD9954 and to run internal state machines.
SCLK maximum frequency is 25 MHz.
CS
CS
is an active low input that enables
—Chip Select.
To write the amplitude scale factor register in LSB first format,
the process is the same as in MSB first; however, the data is bit
wise inverted on a word-by-word basis. The instruction byte is
0x40. The binary data for the ASF is 00000000 00000001.
devices sharing a serial communications line to be individually
programmed. The SDO and SDIO pins go to a high impedance
state when this input is high. If driven high during any
CS
communications cycle, that cycle is suspended until
is
reactivated low. Chip select can be tied low if it is not needed.
CS
● ● ●
SDIO —Serial Data I/O. Data written to the AD9954 must be
sent to this pin. However, this pin can be used as a bidirectional
data line. CFR1<9> controls the configuration of this pin.
SCLK
● ● ●
SDO—Serial Data Out. Data is read from this pin for protocols
that use separate lines for transmitting and receiving data.
When in 2-wire serial programming mode, this pin is set to a
high impedance state.
● ● ●
SDIO
TCSU
TDSU
TDH
TDH
DVDD I/O = 3.3V
DVDD I/O = 1.8V
IOSYNC—synchronizes the I/O port state machines without
affecting the addressable registers contents. An active high input
on the IOSYNC pin aborts the current communication cycle. After
IOSYNC returns low (Logic 0), another communication cycle may
begin, starting with the instruction byte write.
TCSU = 3ns
TDSU = 3ns
TDH = 0ns
TCSU = 5ns
TDSU = 5ns
TDH = 0ns
Figure 29. Timing Diagram for Data Write to AD9954
SCLK
MSB/LSB TRANSFERS
The AD9954 serial port can support either MSB first or LSB
first data formats. This functionality is controlled by the LSB
First Bit CFR1<8>.
SDIO
SDO
TDV = 25ns
For MSB first operation, the serial port controller generates the
most significant byte (of the specified register) address first
followed by the next lesser significant byte addresses until the
I/O operation is complete. All data written to (read from) the
AD9954 must be in MSB first order.
Figure 30. Timing Diagram for Data Read to AD9954
RAM I/O VIA SERIAL PORT
Accessing the RAM via the serial port is identical to any other
serial I/O operation except that the number of bytes transferred
is determined by the address space between the beginning
address and the final address as specified in the current RAM
segment control word (RSCW). The final address describes the
most significant word address for all I/O transfers and the
beginning address specifies the least significant address.
If the LSB mode is active, the serial port controller generates the
least significant byte address first followed by the next greater
significant byte addresses until the I/O operation is complete.
All data written to (read from) the AD9954 must be in LSB
first order.
Example Operation
RAM I/O supports MSB/LSB first operation as set using the
LSB First Bit CFR1<8>. When in MSB first mode, the first data
byte is for the most significant byte of the memory address
described by the final address with the remaining three bytes
making up the lesser significant bytes of that address. The
remaining bytes come in most significant to least significant,
destined for RAM addresses generated in descending order
As an example, consider the case of writing the amplitude scale
factor (ASF) register to a value of 0.5 full scale. First, calculate
the binary equivalent of 0.5. As the ASF is 16 bits wide, the
hexadecimal equivalent is 0x80. Next, for MSB first format,
transmit an instruction byte of 0x02 (serial address of ASF is
00010(b)). From this instruction, the internal controller polls
Rev. C | Page 24 of 40
Data Sheet
AD9954
until the final four bytes are written into the address specified as
the beginning address. When in LSB first mode, the first data
byte is for the least significant byte of the memory (specified by
the beginning address) with the remaining three bytes making
up the greater significant bytes of that address. The remaining
bytes come in least significant to most significant, destined for
RAM addresses generated in ascending order until the final
four bytes are written into the memory address described by the
final address.
INSTRUCTION BYTE
The instruction byte contains the following information.
Table 10.
MSB
D6
D5
D4
D3
D2
D1
LSB
W
X
X
A4
A3
A2
A1
A0
R/
W
R/ —Bit 7 of the instruction byte defines whether a read or
write data transfer occurs after the instruction byte write. Logic
High indicates read operation. Logic 0 indicates a write
operation.
The RAM uses Serial Address 01011(b); therefore, the
instruction byte to write the RAM is 0x0B, in MSB first notation.
As previously mentioned, the RAM addresses generated are
specified by the beginning and final address of the RSCW
currently selected by Pin PS1 and Pin PS0.
X, X—Bit 6 and Bit 5 of the instruction byte are don’t care.
A4, A3, A2, A1, A0—Bit 4, Bit 3, Bit 2, Bit 1, Bit 0 of the
instruction byte determine which register is accessed during the
data transfer portion of the communications cycle. Addresses for
registers can be found in the first column of the register maps (see
Table 12 and Table 13).
Notes on serial port operation
•
The configuration changes made using CFR1<9:8> are
implemented immediately upon writing to this register. For
multibyte transfers, writing to this register may occur
during the middle of a communication cycle. Care must be
taken to compensate for this new configuration for the
remainder of the current communication cycle.
REGISTER MAPS AND DESCRIPTIONS
The register maps are listed in Table 12 and Table 13. The active
register map depends on the state of the linear sweep enable bit;
certain registers are remapped depending on which mode the
part is operating in. Specifically, Register 0x07, Register 0x08,
Register 0x09, and Register 0x0A are affected. Because the
linear sweep operation takes precedence over RAM operations,
Analog Devices, Inc. recommends that the RAM be disabled
using Bit CFR1<31> when linear sweep is enabled by Bit
CFR1<21> to conserve power. The serial address numbers
associated with each of the registers are in hexadecimal format.
Angle brackets <> are used to reference specific bits or ranges of
bits. For example, <3> designates Bit 3 and <7:3> designates the
range of bits from Bit 7 to Bit 3, inclusive.
•
The system must maintain synchronization with the
AD9954 or the internal control logic cannot recognize
further instructions. For example, if the system sends an
instruction byte that describes writing a 2-byte register,
and then pulses the SCLK pin for a 3-byte write (24
additional SCLK rising edges), communication
synchronization is lost. In this case, the first 16 SCLK rising
edges after the instruction cycle properly write the first two
data bytes into the AD9954, but the next eight rising SCLK
edges are interpreted as the next instruction byte. In the case
where synchronization is lost between the system and the
AD9954, the IOSYNC pin enables the user to reset the
AD9954 serial port controller state machine. Any
information that is written to the AD9954 registers during
a valid communication cycle prior to loss of
Table 11. Register Mapping Based on Linear Sweep Enable Bit
Linear Sweep Enable Bit
(CFR1<21>)
Cleared (= 0)
Set (= 1)
Register Map
RAM Segment Control Words Active
Linear Sweep Control Words Active
synchronization and assertion of the IOSYNC pin remain
intact.
•
Reading a RAM profile requires that the profile select pins,
Pin PS1 and Pin PS0, be configured to select the desired
profile. When reading a register that resides in one of the
profiles, the register address acts as an offset to select one of
the registers among the group of registers defined by the
profile, while the profile select pins select the appropriate
register group.
Rev. C | Page 25 of 40
AD9954
Data Sheet
Table 12. Register Map—When Linear Sweep Enable Bit Is False (CFR1<21> = 0)
Note that the RAM Enable Bit CFR1<31> only activates the RAM itself, not the RAM segment control words.
Register
Name
(Serial
Default
Value Or
Profile
Bit
Range
(MSB)
Bit 7
(LSB)
Bit 0
SYNC_CLK Not
Address)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Control
Function
Register
No.1
<7:0>
Digital
Power-
Down
Comp
Power-
Down
DAC
Power-
Down
Clock
Input
Power-
Down
External
Power-
Down
Linear
Sweep
No-
0x00
Disable
Used
Mode
Dwell
(CFR1)
(0x00)
<15:8>
SRR Load
Enable
AutoClr
Freq
Accum
AutoClr Sine/
Clear
Freq
Accum
Clear
Phase
Accum
SDIO
Input
Only
LSB First
0x00
0x00
0x00
Phase
Accum
Cosine
Select
<23:16> Automatic Software
Linear
Sweep
Enable
Not Used
Not
Used
Not Used
Not Used
Not
Used
Sync
Enable
Manual
Sync
<31:24> RAM
Enable
RAM
Destination
Internal Profile Control<2:0>
Load ARR
Control
OSK
Enable
Auto
OSK
Enable
Control
Function
Register
No. 2
(CFR2)
(0x01)
<7:0>
REFCLK Multiplier
Not Used
VCO
Range
Charge Pump
Current<1:0>
0x00
0x00
<15:8>
High
Speed
Sync
Enable
Hardware
Manual
Sync
XTAL
Not
OUT
Used
Enable
Enable
<23:16>
<7:0>
Not Used
Amplitude Scale Factor Register<7:0>
Amplitude Scale Factor Register<13:8>
0x18
0x00
0x00
Amplitude
Scale
Factor (ASF)
<15:8>
Auto Ramp Rate
Speed Control<1:0>
(0x02)
Amplitude
Ramp Rate
(ARR)
<7:0>
Amplitude Ramp Rate Register<7:0>
0x00
(0x03)
Frequency
Tuning
Word
(FTW0)
(0x04)
<7:0>
Frequency Tuning Word No. 0<7:0>
Frequency Tuning Word No. 0<15:8>
Frequency Tuning Word No. 0<23:16>
Frequency Tuning Word No. 0<31:24>
0x00
0x00
0x00
0x00
<15:8>
<23:16>
<31:24>
Phase
<7:0>
Phase Offset Word No. 0<7:0>
0x00
0x00
Offset Word
(POW0)
(0x05)
<15:8>
Not Used<1:0>
Phase Offset Word No. 0<13:8>
Frequency
Tuning
Word
(FTW1)
(0x06)
<7:0>
Frequency Tuning Word No. 1<7:0>
Frequency Tuning Word No. 1<15:8>
Frequency Tuning Word No. 1<23:16>
Frequency Tuning Word No. 1<31:24>
0x00
0x00
0x00
0x00
<15:8>
<23:16>
<31:24>
Profile 0
RAM
<7:0>
RAM Segment 0 Mode
Control<2:0>
No-Dwell
Active
RAM Segment 0 Beginning Address<9:6>
PS0 = 0
PS1 = 0
Segment
Control
Word No. 0
(RSCW0)
(0x07)
<15:8>
<23:16>
<31:24>
<39:32>
RAM Segment 0 Beginning Address<5:0>
RAM Segment 0
Final Address<9:8>
PS0 = 0
PS1 = 0
RAM Segment 0 Final Address<7:0>
PS0 = 0
PS1 = 0
RAM Segment 0 Address Ramp Rate<15:8>
RAM Segment 0 Address Ramp Rate<7:0>
PS0 = 0
PS1 = 0
PS0 = 0
PS1 = 0
Rev. C | Page 26 of 40
Data Sheet
AD9954
Register
Name
(Serial
Default
Value Or
Profile
Bit
Range
(MSB)
Bit 7
(LSB)
Bit 0
Address)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Profile 1
RAM
<7:0>
RAM Segment 1 Mode
Control<2:0>
No-Dwell
Active
RAM Segment 1 Beginning Address<9:6>
PS0 = 1
PS1 = 0
Segment
Control
Word No. 1
(RSCW1)
(0x08)
<15:8>
<23:16>
<31:24>
<39:32>
<7:0>
RAM Segment 1 Beginning Address<5:0>
RAM Segment 1
Final Address<9:8>
PS0 = 1
PS1 = 0
RAM Segment 1 Final Address<7:0>
PS0 = 1
PS1 = 0
RAM Segment 1 Address Ramp Rate<15:8>
RAM Segment 1 Address Ramp Rate<7:0>
PS0 = 1
PS1 = 0
PS0 = 1
PS1 = 0
Profile 2
RAM
RAM Segment 2 Mode
Control<2:0>
No-Dwell
Active
RAM Segment 2 Beginning Address<9:6>
PS0 = 0
PS1 = 1
Segment
Control
Word No. 2
(RSCW2)
(0x09)
<15:8>
<23:16>
<31:24>
<39:32>
<7:0>
RAM Segment 2 Beginning Address <5:0>
RAM Segment 2
Final Address<9:8>
PS0 = 0
PS1 = 1
RAM Segment 2 Final Address<7:0>
PS0 = 0
PS1 = 1
RAM Segment 2 Address Ramp Rate<15:8>
RAM Segment 2 Address Ramp Rate<7:0>
PS0 = 0
PS1 = 1
PS0 = 0
PS1 = 1
Profile 3
RAM
RAM Segment 3 Mode
Control<2:0>
No-Dwell
Active
RAM Segment 3 Beginning Address<9:6>
PS0 = 1
PS1 = 1
Segment
Control
Word No. 3
(RSCW3)
(0x0A)
<15:8>
<23:16>
<31:24>
<39:32>
RAM Segment 3 Beginning Address<5:0>
RAM Segment 3
Final Address <9:8>
PS0 = 1
PS1 = 1
RAM Segment 3 Final Address<7:0>
PS0 = 1
PS1 = 1
RAM Segment 3 Address Ramp Rate<15:8>
RAM Segment 3 Address Ramp Rate<7:0>
PS0 = 1
PS1 = 1
PS0 = 1
PS1 = 1
RAM (0x0B)
RAM [1023:0]<31:0> (Read Instructions Write Out RAM Signature Register Data)
Rev. C | Page 27 of 40
AD9954
Data Sheet
Table 13. Register Map—When Linear Sweep Enable Bit Is True (CFR1<21> = 1)
Note that the RAM Enable Bit CFR1<31> only activates the RAM itself, not the RAM segment control words.
Default
Value Or
Profile
Register Name Bit
(Serial Address) Range
(MSB)
Bit 7
(LSB)
Bit 0
SYNC_CLK Not
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Control
<7:0>
Digital
Power-
Down
Comp
Power-
Down
DAC
Power- Input
Down
Clock
External Linear
0x00
Function
Register No. 1
(CFR1)
Power-
Down
Mode
Sweep
No Dwell
Disable
Used
Power
Down
(0x00)
<15:8>
SRR Load
Enable
AutoClr
Freq
Accum
AutoClr Sine/
Phase Cosine
Accum Select
Clear
Freq
Accum
Clear
Phase
Accum
SDIO
Input
Only
LSB
First
0x00
0x00
0x00
<23:16> Automatic
Software
Manual
Sync
Linear
Sweep
Enable
Not
Used
Not
Used
Not Used Not Used
Not
Used
Sync
Enable
<31:24> RAM
Enable
RAM
Destination
Internal Profile Control<2:0>
Load ARR OSK
Control
Auto
OSK
Enable
Enable
Control
<7:0>
REFCLK Multiplier
Not Used
VCO
Range
Charge Pump
Current<1:0>
0x00
0x00
Function
Register
No. 2 (CFR2)
(0x01)
<15:8>
High
Speed
Sync
Hardware XTAL
Manual
Sync
Not
Used
OUT
Enable
Enable
Enable
<23:16>
Not Used
Amplitude Scale Factor Register<7:0>
0x18
Amplitude
Scale Factor
(ASF) (0x02)
<7:0>
(0x07)
<15:8>
Auto Ramp Rate
Speed Control<1:0>
Amplitude Scale Factor Register<13:8>
Amplitude
Ramp Rate
(ARR) (0x03)
<7:0>
Amplitude Ramp Rate Register<7:0>
Frequency
Tuning
Word
(FTW0)
(0x04)
<7:0>
Frequency Tuning Word No. 0<7:0>
Frequency Tuning Word No. 0<15:8>
Frequency Tuning Word No. 0<23:16>
Frequency Tuning Word No. 0<31:24>
0x00
0x00
0x00
0x00
<15:8>
<23:16>
<31:24>
Phase Offset
Word (POW0)
(0x05)
<7:0>
Phase Offset Word No. 0<7:0>
0x00
0x00
<15:8>
Open<1:0>
Phase Offset Word No. 0<13:8>
Frequency
Tuning
Word (FTW1)
<7:0>
Frequency Tuning Word No. 1<7:0>
Frequency Tuning Word No. 1<15:8>
Frequency Tuning Word No. 1<23:16>
Frequency Tuning Word No. 1<31:24>
<15:8>
<23:16>
<31:24>
<7:0>
(0x06)
Negative
Linear
Sweep
Control
Word (NLSCW)
(0x07)
Falling Delta Frequency Tuning Word<7:0>
Falling Delta Frequency Tuning Word<15:8>
Falling Delta Frequency Tuning Word<23:16>
Falling Delta Frequency Tuning Word<31:24>
Falling Sweep Ramp Rate Word<7:0>
PS0 = 0
PS0 = 0
PS0 = 0
PS0 = 0
PS0 = 0
PS0 = 1
PS0 = 1
PS0 = 1
PS0 = 1
PS0 = 1
<15:8>
<23:16>
<31:24>
<39:32>
<7:0>
Positive
Linear
Sweep
Control
Word (PLSCW)
(0x08)
Rising Delta Frequency Tuning Word<7:0>
Rising Delta Frequency Tuning Word<15:8>
Rising Delta Frequency Tuning Word<23:16>
Rising Delta Frequency Tuning Word <31:24>
Rising Sweep Ramp Rate Word<7:0>
<15:8>
<23:16>
<31:24>
<39:32>
Rev. C | Page 28 of 40
Data Sheet
AD9954
CONTROL REGISTER BIT DESCRIPTIONS
Control Function Register No. 1 (CFR1)
CFR1<22>: Software Manual Synchronization of Multiple
AD9954s
The CFR1 is used to control the various functions, features,
and modes of the AD9954. The functionality of each bit follows.
CFR1<22> = 0 (default). The manual synchronization feature is
inactive.
CFR1<31>: RAM Enable Bit
CFR1<22> = 1. The software-controlled manual synchronization
feature is executed. The SYNC_CLK rising edge is advanced by
one SYNC_CLK cycle, and this bit is autocleared. To advance
the rising edge multiple times, this bit needs to be set once for
each advance.
CFR1<31> = 0 (default). The RAM is disabled for operation.
Either single-tone mode of operation or linear sweep mode of
operation is enabled.
CFR1<31> = 1. The RAM is enabled for operation. Access
control for normal operation is controlled via the mode control
bits of the RSCW for the current profile.
CFR1<21>: Linear Frequency Sweep Enable
CFR1<21> = 0 (default). The linear frequency sweep capability
of the AD9954 is inactive.
CFR1<30>: RAM Destination Bit
If CFR1<31> is cleared, CFR1<30> is ignored.
CFR1<21> = 1. The linear frequency sweep capability of the
AD9954 is enabled. See the Linear Sweep Mode section for details.
CFR1<30> = 0 (default). If CFR1<31> is set, the RAM output
drives the phase accumulator (provides the FTW).
CFR1<20:16>: Not Used, Leave Clear
CFR1<30> = 1. If CFR1<31> is set, the RAM output drives the
phase-offset adder (POW).
CFR1<15>: Linear Sweep Ramp Rate Load Control Bit
CFR1<15> = 0 (default). The linear sweep ramp rate timer is
loaded only upon timeout (timer == 1); it is not loaded due to
an I/O update input signal.
CFR1<29:27>: Internal Profile Control Bits
These bits cause the profile bits to be ignored when the RAM is
being used and puts the AD9954 into an automatic profile loop
sequence that allows the user to implement a frequency/phase
composite sweep that runs without external inputs. See the
Internal Profile Control section for more details.
CFR1<15> = 1. The linear sweep ramp rate timer is loaded
either upon timeout (timer == 1) or at the time of an I/O
update input signal.
CFR1<14>: Autoclear Frequency Accumulator Bit
CFR1<26>: Load Amplitude Ramp Rate Control Bit
CFR1<14> = 0 (default). The current state of the frequency
accumulator is not impacted by receipt of an I/O update signal.
CFR1<26> = 0 (default). The amplitude ramp rate timer is
loaded only upon timeout (timer == 1); it is not loaded due to
an I/O update input signal.
CFR1<14> = 1. The frequency accumulator is automatically and
synchronously cleared for one cycle upon receipt of an I/O
UPDATE signal.
CFR1<26> = 1. The amplitude ramp rate timer is loaded upon
either timeout (timer == 1) or at the time of an I/O update
input signal.
CFR1<13>: Autoclear Phase Accumulator Bit
CFR1<25>: Shaped On-Off Keying Enable Bit
CFR1<13> = 0 (default). The current state of the phase
accumulator is not impacted by receipt of an I/O update signal.
CFR1<25> = 0 (default). Shaped on-off keying is bypassed.
CFR1<13> = 1. The phase accumulator is automatically and
synchronously cleared for one cycle upon receipt of an I/O
update signal.
CFR1<25> = 1. Shaped on-off keying is enabled. See also
CFR1<24>.
CFR1<24>: Autoshaped On-Off Keying Enable Bit
CFR1<12>: Sine/Cosine Select Bit
If CFR1<25> is cleared, CFR1<24> is ignored.
CFR1<12> = 0 (default). The angle-to-amplitude conversion
logic employs a cosine function.
CFR1<24> = 0 (default). Manual shaped on-off keying
operation. See the Shaped On-Off Keying section for details.
CFR1<12> = 1. The angle-to-amplitude conversion logic
employs a sine function.
CFR1<24> = 1. Autoshaped on-off keying operation. See the
Shaped On-Off Keying section for details.
CFR1<11>: Clear Frequency Accumulator
CFR1<23>: Automatic Synchronization Enable Bit
CFR1<11> = 0 (default). The frequency accumulator functions
as normal.
CFR1<23> = 0 (default). The automatic synchronization feature
of multiple AD9954s is inactive.
CFR1<11> = 1. The frequency accumulator memory elements
are cleared and held clear until this bit is cleared.
CFR1<23> = 1. The automatic synchronization feature of
multiple AD9954s is active. See the Synchronizing Multiple
AD9954s section for details.
Rev. C | Page 29 of 40
AD9954
Data Sheet
CFR1<10>: Clear Phase Accumulator
CFR1<2>: Linear Sweep No-Dwell Bit
CFR1<10> = 0 (default). The phase accumulator functions as
normal.
If CFR1<21> is clear, this bit is a don’t care (ignored).
CFR1<2> = 0 (default). The linear sweep no-dwell function is
inactive. If the no-dwell mode is inactive when the sweep
completes, sweeping does not restart until an I/O update or
change in profile initiates another sweep as previously described.
The output frequency holds at the final value in the sweep.
CFR1<10> = 1. The phase accumulator memory elements are
cleared and held clear until this bit is cleared.
CFR1<9>: SDIO Input Only
CFR1<9> = 0 (default). The SDIO pin is bidirectional (2-wire
serial programming mode).
CFR1<2> = 1. The linear sweep no-dwell function is active. If
the no-dwell mode is active when the sweep completes, the
phase accumulator is cleared. The phase accumulator remains
cleared until another sweep is initiated via an I/O update input
or change in profile.
CFR1<9> = 1. The SDIO is configured as an input-only pin
(3-wire serial programming mode).
CFR1<8>: LSB First
CFR1<1>: SYNC_CLK Disable Bit
CFR1<8> = 0 (default). MSB first format is active.
CFR1<8> = 1. LSB first format is active.
CFR1<7>: Digital Power-Down Bit
CFR1<1> = 0 (default). The SYNC_CLK pin is active.
CFR1<1> = 1. The SYNC_CLK pin assumes a static Logic 0
state to minimize noise generated by the digital circuitry. The
synchronization circuitry remains active internally to maintain
normal device timing.
CFR1<7> = 0 (default). All digital functions and clocks are active.
CFR1<7> = 1. All non-I/O digital functionality is suspended,
lowering the power significantly.
CFR1<0>: Not Used, Leave Clear
CFR1<6>: Comparator Power-Down Bit
Control Function Register No. 2 (CFR2)
CFR1<6> = 0 (default). The comparator is enabled for operation.
The CFR2 is used to control the various functions, features, and
modes of the AD9954, primarily related to the analog sections
of the chip.
CFR1<6> = 1. The comparator is disabled and is in its lowest
power dissipation state.
CFR1<5>: DAC Power-Down Bit
CFR2<23:12>: Not Used, Leave Clear
CFR1<5> = 0 (default). The DAC is enabled for operation.
CFR2<11>: High Speed Sync Enable Bit
CFR1<5> = 1. The DAC is disabled and is in its lowest power
dissipation state.
CFR2<11> = 0 (default). The high speed sync enhancement is off.
CFR2<11> = 1. The high speed sync enhancement is on. This
bit should be set when using the autosynchronization feature
for SYNC_CLK > 50 MHz (SYSCLK > 200 MSPS).
CFR1<4>: Clock Input Power-Down Bit
CFR1<4> = 0 (default). The clock input circuitry is enabled for
operation.
CFR2<10>: Hardware Manual Sync Enable Bit
CFR1<4> = 1. The clock input circuitry is disabled and the
device is in its lowest power dissipation state.
CFR2<10> = 0 (default). The hardware manual sync function is off.
CFR2<10> = 1. The hardware manual sync function is enabled.
While this bit is set, a rising edge on the SYNC_IN pin causes
the device to advance the SYNC_CLK rising edge by one
REFCLK cycle. This bit does not self-clear.
CFR1<3>: External Power-Down Mode
CFR1<3> = 0 (default). The external power-down mode
selected is the rapid recovery power-down mode. In this mode,
when the PWRDWNCTL input pin is high, the digital logic
and the DAC digital logic are powered down. The DAC bias
circuitry, PLL, oscillator, and clock input circuitry are not
powered down. CFR1<6> determines whether the comparator
is powered down. CFR1<7>, and CFR1<5:4> are ignored.
CFR2<9>: CRYSTAL OUT Enable Bit
CFR2<9> = 0 (default). The CRYSTAL OUT pin is inactive.
CFR2<9> = 1. The CRYSTAL OUT pin is active. The crystal
oscillator circuitry output drives the CRYSTAL OUT pin, which
can be used as a reference frequency for additional devices.
CFR1<3> = 1. The external power-down mode selected is the
full power-down mode. In this mode, when the PWRDWNCTL
input pin is high, all functions are powered down. This includes
the DAC and PLL, which take a significant amount of time to
power up. CFR1<7:4> are all ignored.
CFR2<8>: Not Used, Leave Clear
CFR2<7:3>: Reference Clock Multiplier Control Bits
This 5-bit word controls the multiplier value out of the clock-
multiplier (PLL) block. See the Clock Multiplier section for
more details.
Rev. C | Page 30 of 40
Data Sheet
AD9954
RAM Segment Control Words (RSCW0, RSCW1, RSCW2,
and RSCW3)
CFR2<2>: VCO Range Control Bit
CFR2<2> = 0 (default), VCO operates between 100 MHz and
250 MHz.
When linear sweep is disabled, Register 0x07, Register 0x08,
Register 0x09, and Register 0x0A act as the RAM segment
control words for each of the RAM segments. Each of the RAM
segment control words is comprised of a RAM segment address
ramp rate, a final address value, a beginning address value, a
RAM segment mode control, and a no-dwell bit. Note the
discontinuities of the address registers, since they may make
programming a little more challenging.
CFR2<2> = 1, VCO operates between 250 MHz and 400 MHz.
CFR2<1:0>: Charge Pump Current Control Bits
These bits are used to control the current setting on the charge
pump. The default setting, CFR2<1:0>, sets the charge pump
current to the default value of 75 µA. For each bit added, 25 µA
of current is added to the charge pump current:
01 = 100 µA, 10 = 125 µA, and 11 = 150 µA.
RAM Segment Address Ramp Rate, RSCW<39:24>
OTHER REGISTER DESCRIPTIONS
Amplitude Scale Factor (ASF)
For RAM modes that step through address values, such as
ramping, this 16-bit word defines the number of SYNC_CLK
cycles the RAM controller dwells at each address. A value of 0 is
invalid. Any other value from 1 to 65,535 can be used.
The ASF register stores the 2-bit auto ramp rate speed value and
the 14-bit amplitude scale factor used in the output shaped
keying (OSK) operation. In auto-OSK operation, ASF<15:14>
tells the OSK block how many amplitude steps to take for each
increment or decrement. ASF<13:0> sets the maximum value
achievable by the OSK internal multiplier. In manual OSK
mode, ASF<15:14> has no effect. ASF<13:0> provide the output
scale factor directly. If the OSK is disabled using CFR1<25>,
this register has no effect on device operation.
RAM Segment Final Address RSCW<9:8>, RSCW<23:16>
This discontinuous 10-bit sequence defines the final address
value for the given RAM segment. The order in which the bits
are previously listed is MSB first: RSCW<9> is the MSB and
RSCW<16> is the LSB of the final address value.
RAM Segment Beginning Address RSCW<3:0>,
RSCW <15:10>
Amplitude Ramp Rate (ARR)
This discontinuous 10-bit sequence defines the final address
value for the given RAM segment. The order in which the bits
are previously listed is MSB first: RSCW<3> is the MSB and
RSCW<10> is the LSB of the final address value.
The ARR register stores the 8-bit amplitude ramp rate used in
the auto-OSK mode. See the Amplitude Control Options
section for details.
Frequency Tuning Word 0 (FTW0)
RAM Segment No-Dwell Bit RSCW<4>
The frequency tuning word is a 32-bit register that controls the
rate of accumulation in the phase accumulator of the DDS core.
Its specific role is dependent on the device mode of operation.
This bit sets the no-dwell feature of sweeping profiles. In
profiles that sweep from a defined beginning to a defined end,
the RAM controller can either dwell at the final address until
the next profile is selected or, when this bit is set, the RAM
controller returns to the beginning address and dwells there
until the next profile is selected.
Phase Offset Word (POW)
The phase offset word is a 14-bit register that stores a phase
offset value. See the Phase Offset Word Mux section for
additional details.
RAM Segment Mode Control RSCW<7:5>
Frequency Tuning Word 1 (FTW1)
This 3-bit sequence determines the RAM segment’s mode of
operation. There are only five possible RAM modes, so only
values of 0 to 4 are valid (see Table 7).
The frequency tuning word is a 32-bit register that sets the
upper frequency in a linear sweep operation.
Register 0x07 and Register 0x08 are multifunctional registers.
Negative and Positive Linear Sweep Control Word
(NLSCW and PLSCW)
When linear sweep bit is enabled, Register 0x07 provides the
negative linear sweep control word (NLSCW) and Register 0x08
provides the positive linear sweep control word (PLSCW). Each
of the linear sweep control words contains a 32-bit delta frequency
tuning word (FDFTW and RDFTW) and an 8-bit sweep ramp
rate word (FSRRW and RSRRW). See the Modes of Operation
section for more details.
Rev. C | Page 31 of 40
AD9954
Data Sheet
LAYOUT CONSIDERATIONS
For the best performance, the following layout guidelines
should be observed. Always separate the analog power supply
(AVDD) and the digital power supply (DVDD), even if just
from two different voltage regulators driven by a common
supply. Likewise, the ground connections (AGND and DGND)
should be kept separate as far back to the source as possible (for
example, separate the ground planes on a localized board, even
if the grounds connect to a common point in the system).
Bypass capacitors should be placed as close to device pins as
possible. Usually a multitiered bypassing scheme consisting of a
small high frequency capacitor (100 pF) placed close to the
supply pin and progressively larger capacitors (0.1 µF and 10 µF)
further back to the actual supply source works best.
Rev. C | Page 32 of 40
Data Sheet
AD9954
DETAILED PROGRAMMING EXAMPLES
The last example programmed the clock multiplier; therefore,
start with a 400 MSPS clock. FTW0 is (61.53/400) × 232 or
0x27611340, and FTW1 is (62.73/400) × 232 or 0x2825AEE6.
To turn the linear sweep on, set CFR1<21>.
SINGLE-TONE MODE
1. Write to Control Register 1 instructing the part to
autoclear the phase accumulator whenever the phase offset
word changes and issues an I/O update. Set Bit 13 in the
CFR1 register. The address for CFR1 is 0; therefore, an
instruction byte of 0x00 is sent and 0x00 00 00 20 for data.
Note that users must write to all four bytes of the register.
2. Write to Control Register 2 setting the clock multiplier
value to 20, and the VCO range bit to its upper value. In
CFR2, Bit 7 to Bit 3 control the multiply value. To get a
multiplied value of 20 from 5 bits, the binary value is
10100. As previously mentioned, also send Bit 2 to put the
VCO into its upper range (to get 400 MHz). Therefore, the
instruction byte is 0x01 and 0x00 00 A4 for data.
3. Calculate the tuning word to generate a 122 MHz output
from a 400 MSPS clock, load it into FTW0, and latch the
data written to the I/O buffers into their respective
registers. The frequency tuning word equation becomes
(122 MHz/ 400 MHz) × 232, which yields 0x4E 14 7A E1.
Send the Instruction Byte 0x04 and four data bytes of 0x4E
14 7A E1. Issue an I/O update, which transfers the data
into the part.
The PLSCW and NLSCW are five bytes wide: one byte for the
ramp rate and four bytes for the incremental frequency value.
To begin, calculate the ramp rate, and cover 1.2 MHz on both
sweeps. The ramp rate tells the part how many SYNC_CLK
cycles (for SYSCLK cycles) to send at each incremental value.
When the shortest time possible is spent at each incremental
frequency, the most linearized sweep is achieved; therefore, the part
should only spend one SYNC_CLK period at each incremental
frequency, which ensures that the smallest frequency steps possible
are taken. For a 400 MSPS SYSCLK, the result is a 100 MHz
SYNC_CLK rate or a 10 ns SYNC_CLK period. This means on the
finest resolution, 120 incremental steps squeeze into the rising
sweep (1.2 µs/10 ns) and 180 on the falling sweep (1.8 µs/10 ns).
For the rising delta frequency, a 1.2 MHz/120 steps is calculated,
which means each step is approximately 10 kHz for the rising
delta frequency and approximately 666.6666 Hz for the falling
delta frequency. The logic in the linear sweep block ensures that
FTW1 on a rising sweep or FTW0 on a falling sweep is not
exceeded. If the exact incremental tuning word is not achieved
using the 32-bit resolution, round up, not down, to ensure the
entire range during the sweep is covered. To calculate the rising
Whenever a phase change is desired, calculate and write
the phase offset word to the part and issue an I/O update.
For example, if the first value is 45°, the phase offset word
is (45/360) × 214, or in decimal, 2048. Therefore, write an
instruction byte of 0x05 and Data Byte 0x0800. When an
I/O update is issued, the phase accumulator clears, which
starts it from a known phase of 0°. It again accumulates at a
122 MHz rate, except now phase shifting each and every
sample by 45°.
delta frequency word, simply calculate (10 K/400 M) × 232
=
0x0001A36F. Combining the rising ramp rate, first byte, and the
rising delta frequency, the second byte to fifth byte yields the
PLSCW: 0x010001A36F. Likewise, the NLSCW works out to
0x0100001BF4. Table 14 is a summary table of instruction and
data bytes to write to.
In this example, the part is programmed to output a 122 MHz
single-tone carrier, the device is clocked with a 20 MHz crystal
oscillator, and the clock multiplier is used to push the internal
system clock up to 400 MHz. Phase offsets are then added to
the carrier.
Table 14. Linear Sweep Example Write Instructions
Register
Instruction Byte
Data Byte
CFR1
FTW0
FTW1
NLSCW
RLSCW
0x00
0x04
0x06
0x07
0x08
0x00200000
0x27611340
0x2825AEE6
0x0100001BF4
0x010001A36F
The programming steps include the following:
LINEAR SWEEP MODE
In this example, the part is programmed to generate a chirp
from 61.53 MHz to 62.73 MHz. The chirp up is in 1.20 µs,
the chirp down is in 1.8 µs, and the chirp is made as finely
linearized as possible. Therefore, users must calculate and
program:
RAM MODE
This example programs the RAM. Use the RAM on the AD9954
to simulate the nonlinear filter shape of a Gaussian filter response
on the FSK data. Begin by plotting the filter response from F0 to
F1 and from F1 to F0. The transition time specification (see
Table 1) tells how long it takes to transition from F0 to F1 and
from F1 to F0, either as an actual time value or as a fraction of
the symbol rate. Both ways show how long it can take to change
symbols, and for this application, it is 100 ns. To program the
RAM, decide how many RAM segments to use, program the
RAM segment control word for each of those segments, and
load the RAM data for each of those segments.
•
•
•
•
FTW0 for 61.53 MHz (the start frequency)
FTW1 for 62.73 MHz (the stop frequency)
CFR1 to put the part into linear sweep mode
The positive linear sweep control word (PLSCW), to make
as linearized a chirp in 1.20 µs
•
The negative linear sweep control word (NLSCW), to make
as linearized a chirp in 1.80 µs
Rev. C | Page 33 of 40
AD9954
Data Sheet
Table 15. RAM Mode Register Table Settings
Because there is a ramp-up, but no ramp-down, RAM mode,
two RAM segments are generated; one for the transition from
F0 to F1, and one for the transition from F1 to F0. Step through
the intermediary frequencies as quickly as possible, because the
faster the steps, the less the output frequency deviates from the
ideal frequency response of the filter. The fastest the AD9954
can step through the values in the RAM is at the SYNC_CLK
rate, or ¼ of the SYSCLK rate, which works out to 10 ns,
assuming the maximum SYSCLK rate of 400 MSPS. Dividing
the total transition time of 100 ns by the time for each transition,
100 steps can be taken. The intermediary frequencies are solved
by looking at the instantaneous frequency on the curve every
10 ns and by recording that value. This gives 200 frequency
values, 100 representing the change from F0 to F1 and 100
representing the change from F1 to F0. This is the information
needed to program the RAM.
RAM
<7:0>
RAM
Segment 1
Mode Control Active Address <9:6>
No-
Dwell
RAM Segment 1
Beginning
Segment
Control
Word
<2:0>
001
0
0001
No. 1
(RSCW1)
(0x08)
<15:8>
RAM Segment 1
Beginning
Address <5:0>
RAM Segment 1
Final Address <9:8>
00
100100
<23:16>
<31:24>
<39:32>
RAM Segment 1 Final Address <7:0>
11000111
RAM Segment 1 Address Ramp Rate
<15:8> 00000000
RAM Segment 1 Address Ramp Rate
<7:0> 00010000
The RSCW0 and RSCW1 values must be loaded into their
registers before attempting to write data to RSCW0 and
RSCW1; therefore, issue an I/O update.
Begin by programming CFR1 to set the RAM enable bit.
Calculate and program RSCW0 and RSCW1. Each of the RAM
segment control words has an address ramp rate (16 bits), a
final address (10 bits), a beginning address (10 bits), a mode
control value (3 bits), and a no-dwell flag. Stepping through the
intermediary frequencies as quickly as possible was previously
discussed; therefore, the ramp rate for each word is 0x0000.
Define RAM Segment 0 to occupy the RAM space from
Address 0 to Address 99, which gives 100 values. Define RAM
Segment 1 to occupy Address 100 to Address 199 (also 100
values). Look at the modes of operation choice and recognize
that the ramp-up mode is used to step through each of the
addresses and then holds the final value in the profile.
Therefore, for each RSCW, the mode control bits are b’001.
Because staying at the last value is recommended, the no-dwell
bit is 0. To form the data for each RSCW, combine these values.
For RSCW0, it is 0x0100630020. For RSCW1, it is
0x0100C79021. Because the words that comprise the RSCW are
not contiguous, care must be taken in calculating the RSCW.
Make a chart of each of the subwords in order: address ramp
rate, final address, beginning address, mode, and no dwell.
Write the binary values for each subword, and then, with a copy
of the register map printed out, write each of the binary bits into the
map. When this is completed, the individual bytes can be read from
the map. For example, Table 15 shows how RSCW1 would appear.
The next step is to convert each of the intermediary frequencies
into a frequency tuning word according to
fi
ftw =
×232
SYSCLK
where:
fi is the desired intermediary frequency.
SYSCLK is the system clock rate.
Once this is complete, the result for each profile should be a
vector of 100 32-bit words. To write RAM Segment 0, select
Profile 0 (PS0 = 0, PS1 = 0), and then write the instruction byte
b’00001011, which indicates a RAM write operation is going to
be performed. The serial port I/O controller recognizes this and
polls the profile select pins, thus determining that Profile 0 is
the target storage location for the data out of RSCW0 previously
entered. It now knows to put the first word at Address 0, the last
word at Address 99, and that there are 100 words in total.
Proceed to load all 100 32-bit frequency words into the RAM.
When this is done, write the data to RAM Segment 1. First,
change to Profile 1 (PS0 = 1, PS1 = 0), and then write the RAM
instruction byte again. The device now knows to write the first
word at Address 100, the last word at Address 199, and again
that there are 100 words in total. Write all 100 32-bit words of
RAM Segment 1 and issue an I/O update. Whenever the PS0
pin is toggled (from 0 to 1), the part steps through the RAM
segment, which is the Gaussian-shaped pattern programmed
into the RAM.
Rev. C | Page 34 of 40
Data Sheet
AD9954
SUGGESTED APPLICATION CIRCUITS
FREQUENCY
TUNING
WORD
PHASE
OFFSET
WORD 1
MODULATED/
DEMODULATED
SIGNAL
RF/IF INPUT
I/I-BAR
BASEBAND
LPF
AD9954
REFCLK
REFCLK
IOUT
IOUT
CRYSTAL
LPF
AD9954 DDS
Figure 31. Synchronized LO for Upconversion/Downconversion
REFCLK
CRYSTAL OUT SYNC_OUT
RF OUT
PHASE
COMPARATOR
LOOP
FILTER
REF
SIGNAL
SYNC_IN
VCO
IOUT
AD9954 DDS
IOUT
LPF
FILTER
AD9954
REFCLK
Q/Q-BAR
BASEBAND
TUNING
WORD
FREQUENCY
TUNING
WORD
PHASE
OFFSET
WORD 2
Figure 32. Digitally Programmable Divide-by-N Function in PLL
Figure 34. Two AD9954s Synchronized to Provide I and
Q Carriers with Independent Phase Offsets for Nulling
TUNING WORD
IOUT
IOUT
LPF
LPF
AD9954 DDS
AD9954
ON-CHIP
COMPARATOR
CMOS LEVEL CLOCK
Figure 33. Frequency Agile Clock Generator
Rev. C | Page 35 of 40
AD9954
Data Sheet
EVALUATION BOARD SCHEMATICS
T
S E
R _
D A C
4 2
1 T D _ U N C S _ Y I / O
O D S
C N S Y I O
O D S
7 3
8 3
9 3
0 4
1 4
2 4
3 4
4 4
5 4
6 4
7 4
8 4
P
D A C B
3 2
D N G A
D N G
1 T D _ U B S C
K L C S
S C
2 2
1 2
0 2
9 1
8 1
7 1
6 1
5 1
4 1
3 1
T U I O
K L C S
T U I O
D D V A
D D V A
O I D S
O I D S
D D V A
D D V A
D N G
D N G
D N G D
O I / _ D V D D
N I _ N C S Y
K L C _ N C S Y
S K O
O I / _ D V D D
D N G A
D D V A
D N G A
D N G A
D D V A
1 T D _ U I L T U M N C S Y
2 T D _ U I L T U M N C S Y
1 T D _ U K S O
1 T D U 0 _ P S
1 T D U 1 _ P S
D D V A
D N G
D N G
P S 0
D D V A
P S 1
Figure 35. Evaluation Board Channel 1
Rev. C | Page 36 of 40
Data Sheet
AD9954
T
S E
R _
D A C
4 2
2 T D _ U N C S _ Y I / O
C N S Y I O
O D S
7 3
8 3
9 3
0 4
1 4
2 4
3 4
4 4
5 4
6 4
7 4
8 4
P
D A C B
O D S
2 T D _ U B S C
K L C S
3 2
D N G A
D N G
S C
2 2
1 2
0 2
9 1
8 1
7 1
6 1
5 1
4 1
3 1
T U I O
K L C S
T U I O
D D V A
D D V A
O I D S
O I D S
D D V A
D D V A
D N G
D N G
D N G D
O I / _ D V D D
N I _ N C S Y
K L C _ N C S Y
S K O
O I / _ D V D D
D N G A
D D V A
D N G A
D N G A
D D V A
2 T D _ U I L T U M N C S Y
1 T D _ U I L T U M N C S Y
2 T D _ U K S O
2 T D U 0 _ P S
2 T D U 1 _ P S
D D V A
D N G
D N G
P S 0
D D V A
P S 1
Figure 36. Evaluation Board Channel 2
Rev. C | Page 37 of 40
AD9954
Data Sheet
5
4
3
2
1
Figure 37. Evaluation Board Interface Logic
Rev. C | Page 38 of 40
Data Sheet
AD9954
OUTLINE DIMENSIONS
1.20
MAX
9.00
BSC SQ
0.75
0.60
0.45
BOTTOM VIEW
(PINS UP)
37
36
48
37
36
48
1
1
7.00
BSC SQ
PIN 1
TOP VIEW
(PINS DOWN)
3.50
SQ
0° MIN
1.05
1.00
0.95
0.20
0.09
7°
3.5°
0°
EXPOSED
PAD
12
25
24
25
24
12
13
13
0.15
0.05
SEATING
PLANE
VIEW A
0.08 MAX
COPLANARITY
0.50 BSC
LEAD PITCH
0.27
0.22
0.17
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-ABC
Figure 38. 48-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
(SV-48-4)
Dimensions shown in millimeters
ORDERING GUIDE
Temperature
Range
Ordering
Quantity
Package
Model1
Package Description
Option
SV-48-4
SV-48-4
AD9954YSVZ
AD9954YSVZ-REEL7
AD9954/PCBZ
−40°C to +105°C
−40°C to +105°C
48-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
48-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
Evaluation Board
500
1 Z = RoHS Compliant Part.
Rev. C | Page 39 of 40
AD9954
NOTES
Data Sheet
©2003–2017 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D03374-0-2/17(C)
相关型号：
AD9956XCPZ
IC SPECIALTY ANALOG CIRCUIT, QCC48, 7 X 7 MM, MO-220-VKKD-2, LFCSP-48, Analog IC:Other
ADI
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