AD9273BSVZ-40 [ADI]
Octal LNA/VGA/AAF/ADC and Crosspoint Switch;型号: | AD9273BSVZ-40 |
厂家: | ADI |
描述: | Octal LNA/VGA/AAF/ADC and Crosspoint Switch |
文件: | 总49页 (文件大小:706K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
Octal LNA/VGA/AAF/ADC
and Crosspoint Switch
AD9273
FUNCTIONAL BLOCK DIAGRAM
FEATURES
8 channels of LNA, VGA, AAF, and ADC
Low noise preamplifier (LNA)
Input-referred noise voltage = 1.26 nV/√Hz
(gain = 21.3 dB) @ 5 MHz typical
LOSW-A
LO-A
AD9273
SPI-programmable gain = 15.6 dB/17.9 dB/21.3 dB
Single-ended input; VIN maximum = 733 mV p-p/
550 mV p-p/367 mV p-p
Dual-mode active input impedance matching
Bandwidth (BW) > 100 MHz
Full-scale (FS) output = 4.4 V p-p differential
Variable gain amplifier (VGA)
Attenuator range = −42 dB to 0 dB
SPI-programmable PGA gain = 21 dB/24 dB/27 dB/30 dB
Linear-in-dB gain control
Antialiasing filter (AAF)
Programmable 2nd-order low-pass filter (LPF) from
8 MHz to 18 MHz
Programmable high-pass filter (HPF)
Analog-to-digital converter (ADC)
12 bits at 10 MSPS to 50 MSPS
LI-A
12-BIT
ADC
DOUTA+
DOUTA–
SERIAL
LVDS
LNA
LNA
LNA
LNA
LNA
LNA
LNA
LNA
VGA
VGA
LG-A
AAF
AAF
AAF
AAF
AAF
AAF
AAF
AAF
LOSW-B
LO-B
LI-B
12-BIT
ADC
DOUTB+
DOUTB–
SERIAL
LVDS
LG-B
LOSW-C
LO-C
LI-C
12-BIT
ADC
DOUTC+
DOUTC–
SERIAL
LVDS
VGA
VGA
LG-C
LOSW-D
LO-D
LI-D
12-BIT
ADC
DOUTD+
DOUTD–
SERIAL
LVDS
LG-D
LOSW-E
LO-E
LI-E
DOUTE+
DOUTE–
12-BIT
ADC
SERIAL
LVDS
VGA
LG-E
LOSW-F
LO-F
LI-F
DOUTF+
DOUTF–
SNR = 70 dB
SFDR = 75 dB
12-BIT
ADC
SERIAL
LVDS
VGA
VGA
LG-F
LOSW-G
LO-G
Serial LVDS (ANSI-644, IEEE 1596.3 reduced range link)
Data and frame clock outputs
Includes an 8 × 8 differential crosspoint switch to support
continuous wave (CW) Doppler
Low power, 109 mW per channel at 12 bits/40 MSPS (TGC)
70 mW per channel in CW Doppler
Flexible power-down modes
LI-G
DOUTG+
DOUTG–
12-BIT
ADC
SERIAL
LVDS
LG-G
LOSW-H
LO-H
LI-H
12-BIT
ADC
DOUTH+
DOUTH–
SERIAL
LVDS
VGA
LG-H
Overload recovery in <10 ns
Fast recovery from low power standby mode, <2 μs
100-lead TQFP and 144-ball BGA
FCO+
FCO–
DCO+
DCO–
REFERENCE
SWITCH
ARRAY
APPLICATIONS
Medical imaging/ultrasound
Automotive radar
GENERAL DESCRIPTION
Figure 1.
The AD9273 is designed for low cost, low power, small size, and
ease of use. It contains eight channels of a low noise preamplifier
(LNA) with a variable gain amplifier (VGA); an antialiasing
filter (AAF); and a 12-bit, 10 MSPS to 50 MSPS analog-to-
digital converter (ADC).
The LNA has a single-ended-to-differential gain that is selectable
through the SPI. The LNA input-referred noise voltage is typically
1.26 nV/√Hz at a gain of 21.3 dB, and the combined input-referred
noise voltage of the entire channel is 1.42 nV/√Hz at typical
gain. Assuming a 15 MHz noise bandwidth (NBW) and a 21.3 dB
LNA gain, the input SNR is about 91 dB. In CW Doppler mode,
the LNA output drives a transconductance amp that is switched
through an 8 × 8 differential crosspoint switch. The switch is
programmable through the SPI.
Each channel features a variable gain range of 42 dB, a fully
differential signal path, an active input preamplifier termination, a
maximum gain of up to 52 dB, and an ADC with a conversion
rate of up to 50 MSPS. The channel is optimized for dynamic
performance and low power in applications where a small
package size is critical.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and 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
Fax: 781.461.3113
www.analog.com
©2009 Analog Devices, Inc. All rights reserved.
AD9273* PRODUCT PAGE QUICK LINKS
Last Content Update: 02/23/2017
COMPARABLE PARTS
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REFERENCE MATERIALS
Press
• Industry’s First Octal Ultrasound Receiver with Digital I/Q
Demodulator and Decimation Filter Reduces Processor
Overhead in Ultrasound Systems
EVALUATION KITS
• AD9273 Evaluation Board
• Low Cost, Octal Ultrasound Receiver with On-Chip RF
Decimator and JESD204B Serial Interface
DOCUMENTATION
Application Notes
Technical Articles
• MS-2210: Designing Power Supplies for High Speed ADC
• AN-1142: Techniques for High Speed ADC PCB Layout
• AN-586: LVDS Outputs for High Speed A/D Converters
• AN-737: How ADIsimADC Models an ADC
• New Components Offer Fexibility in Ultrasound System
Design
• Processors for Ultrasound Improve Image Quality
• AN-812: MicroController-Based Serial Port Interface (SPI)
Boot Circuit
DESIGN RESOURCES
• AD9273 Material Declaration
• PCN-PDN Information
• Quality And Reliability
• Symbols and Footprints
• AN-835: Understanding High Speed ADC Testing and
Evaluation
• AN-877: Interfacing to High Speed ADCs via SPI
• AN-878: High Speed ADC SPI Control Software
• AN-905: Visual Analog Converter Evaluation Tool Version
1.0 User Manual
DISCUSSIONS
• AN-935: Designing an ADC Transformer-Coupled Front
End
View all AD9273 EngineerZone Discussions.
Data Sheet
SAMPLE AND BUY
• AD9273: Octal LNA/VGA/AAF/ADC and Crosspoint Switch
Data Sheet
Visit the product page to see pricing options.
SOFTWARE AND SYSTEMS REQUIREMENTS
TECHNICAL SUPPORT
• UG-001: Evaluation Board User Guide
Submit a technical question or find your regional support
number.
TOOLS AND SIMULATIONS
• Visual Analog
DOCUMENT FEEDBACK
Submit feedback for this data sheet.
• AD9273 IBIS Models
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AD9273
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation ...................................................................... 21
Ultrasound .................................................................................. 21
Channel Overview ..................................................................... 22
Input Overdrive .......................................................................... 25
CW Doppler Operation............................................................. 25
TGC Operation........................................................................... 27
ADC ............................................................................................. 31
Clock Input Considerations...................................................... 31
Serial Port Interface (SPI).............................................................. 38
Hardware Interface..................................................................... 38
Memory Map .................................................................................. 40
Reading the Memory Map Table.............................................. 40
Reserved Locations .................................................................... 40
Default Values............................................................................. 40
Logic Levels................................................................................. 40
Outline Dimensions....................................................................... 44
Ordering Guide .......................................................................... 45
Applications....................................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Product Highlights ........................................................................... 3
Specifications..................................................................................... 4
AC Specifications.......................................................................... 4
Digital Specifications ................................................................... 8
Switching Specifications .............................................................. 9
ADC Timing Diagrams ................................................................. 10
Absolute Maximum Ratings.......................................................... 11
Thermal Impedance................................................................... 11
ESD Caution................................................................................ 11
Pin Configuration and Function Descriptions........................... 12
Typical Performance Characteristics ........................................... 15
Equivalent Circuits......................................................................... 19
REVISION HISTORY
7/09—Rev. A to Rev. B
Changes to Ultrasound Section.................................................... 21
Changes to Low Noise Amplifier (LNA) Section....................... 22
Changes to Active Impedance Matching Section and
Figure 40...................................................................................... 23
Changes to LNA Noise Section .................................................... 24
Changes to Input Overload Protection Section and Figure 44 .......25
Changes to Figure 48...................................................................... 28
Changes to Figure 49 and Figure 50............................................. 29
Changes to Clock Input Considerations Section and to
Figure 56 to Figure 59................................................................ 31
Changes to Digital Outputs and Timing Section....................... 33
Changes to CSB Pin Section ......................................................... 36
Changes to Reading the Memory Map Table Section ............... 40
Updated Outline Dimensions....................................................... 44
Changes to Ordering Guide.......................................................... 45
Added BGA Package ..........................................................Universal
Changes to Features and General Description Sections.............. 1
Changes to Product Highlights Section......................................... 3
Changes to Full-Channel (TGC) Characteristics Parameter,
Table 1 ............................................................................................ 4
Changes to Gain Control Interface Parameter and to CW
Doppler Mode Parameter, Table 1.............................................. 6
Change to Wake-Up Time (Standby), GAIN+ = 0.8 V
Parameter....................................................................................... 9
Changes to Figure 2 and Figure 3................................................. 10
Changes to Table 4.......................................................................... 11
Addded Figure 5; Renumbered Sequentially .............................. 12
Changes to Table 6.......................................................................... 13
Changes to Figure 34 and Figure 35............................................. 20
4/09—Revision A: Initial Version
Rev. B | Page 2 of 48
AD9273
The AD9273 requires a LVPECL-/CMOS-/LVDS-compatible
sample rate clock for full performance operation. No external
reference or driver components are required for many
applications.
Fabricated in an advanced CMOS process, the AD9273 is
available in a 16 mm × 16 mm, RoHS compliant, 100-lead
TQFP or a 144-ball BGA. It is specified over the industrial
temperature range of −40°C to +85°C.
The ADC automatically multiplies the sample rate clock for
the appropriate LVDS serial data rate. A data clock (DCO ) for
capturing data on the output and a frame clock (FCO ) trigger
for signaling a new output byte are provided.
PRODUCT HIGHLIGHTS
1. Small Footprint. Eight channels are contained in a small,
space-saving package. A full TGC path, ADC, and crosspoint
switch contained within a 100-lead, 16 mm × 16 mm TQFP or
a 144-ball BGA.
2. Low Power of 109 mW per Channel at 40 MSPS.
3. Integrated Crosspoint Switch. This switch allows numerous
multichannel configuration options to enable the CW
Doppler mode.
4. Ease of Use. A data clock output (DCO ) operates up to
300 MHz and supports double data rate (DDR) operation.
5. User Flexibility. Serial port interface (SPI) control offers a wide
range of flexible features to meet specific system requirements.
6. Integrated Second-Order Antialiasing Filter. This filter is
placed between the VGA and the ADC and is programmable
from 8 MHz to 18 MHz.
Powering down individual channels is supported to increase
battery life for portable applications. There is also a standby
mode option that allows quick power-up for power cycling. In
CW Doppler operation, the VGA, AAF, and ADC are powered
down. The power of the time gain control (TGC) path scales
with selectable speed grades.
The ADC contains several features designed to maximize flexibility
and minimize system cost, such as a programmable clock, data
alignment, and programmable digital test pattern generation. The
digital test patterns include built-in fixed patterns, built-in
pseudorandom patterns, and custom user-defined test patterns
entered via the serial port interface.
Rev. B | Page 3 of 48
AD9273
SPECIFICATIONS
AC SPECIFICATIONS
AVDD1 = 1.8 V, AVDD2 = 3.0 V, DRVDD = 1.8 V, 1.0 V internal ADC reference, fIN = 5 MHz, RS = 50 Ω, LNA gain = 21.3 dB, LNA bias =mid-
high (default), PGA gain = 24 dB, GAIN− = 0.8 V, AAF LPF cutoff = fSAMPLE/3 (default), HPF = LPF cutoff/20.7 (default), full temperature,
ANSI-644 LVDS mode, unless otherwise noted.
Table 1.
AD9273-25
Typ
AD9273-40
Typ
AD9273-50
Typ
Parameter1
LNA CHARACTERISTICS
Gain
Conditions
Min
Max Min
Max Min
Max
Unit
Single-ended
input to
differential
output
15.6/17.9/21.3
9.6/11.9/15.3
733/550/367
15.6/17.9/21.3
9.6/11.9/15.3
733/550/367
15.6/17.9/21.3
9.6/11.9/15.3
733/550/367
dB
Single-ended
input to
single-ended
output
dB
Input Voltage Range LNA gain =
mV p-p
SE2
15.6 dB/
17.9 dB/
21.3 dB,
LNA output
limited to
4.4 V p-p
differential
output
Input Common
Mode
0.9
0.9
0.9
V
Input Resistance
RFB = 250 Ω
RFB = 500 Ω
RFB = ∞
50
50
50
Ω
100
100
100
Ω
15
15
15
kΩ
Input Capacitance
−3 dB Bandwidth
LI-x
22
22
22
pF
70
70
70
MHz
nV/√Hz
Input-Referred
Noise Voltage
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB,
1.6/1.42/1.26
1.6/1.42/1.26
1.6/1.42/1.26
RS = 0 Ω,
R
FB = ∞
Input Noise Current
RFB = ∞
1
1
1
pA/√Hz
mV p-p
1 dB Input Com-
pression Point
LNA gain =
15.6 dB/
1.0/0.8/0.5
1.0/0.8/0.5
1.0/0.8/0.5
17.9 dB/
21.3 dB,
GAIN+ = 0 V
Noise Figure
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB
Active Termina-
tion Matched
RS = 50 Ω,
RFB = 200 Ω/
250 Ω/350 Ω
5.8/5.1/4.3
6.3/5.3/4.4
5.8/5.1/4.3
6.3/5.3/4.4
5.8/5.1/4.3
6.3/5.3/4.4
dB
dB
Unterminated
RFB = ∞
FULL-CHANNEL (TGC)
CHARACTERISTICS
AAF Low-Pass Filter
Cutoff
In range, −3 dB,
programmable
Out of range,3
−3 dB, pro-
8 to 18
8 to 18
8 to 18
MHz
MHz
5 to 8, 18 to 35
5 to 8, 18 to 35
5 to 8, 18 to 35
grammable,
>>AAF band-
width tolerance
Rev. B | Page 4 of 48
AD9273
AD9273-25
Typ
AD9273-40
Typ
AD9273-50
Typ
Parameter1
Conditions
Min
Max Min
Max Min
Max
Unit
AAF Bandwidth
Tolerance
In range
10
10
10
%
Group Delay
Variation
f = 1 MHz to
18 MHz,
2
2
2
ns
GAIN+ = 0 V to
1.6 V
Input-Referred
Noise Voltage
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB,
1.94/1.64/1.38
1.94/1.64/1.38
1.94/1.64/1.38
nV/√Hz
R
FB = ∞
Noise Figure
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB
Active Termina-
tion Matched
RS = 50 Ω,
10.3/8.7/6.8
10.3/8.6/6.7
10.3/8.6/6.7
dB
RFB = 200 Ω/
250 Ω/350 Ω
Unterminated
RFB = ∞
7.1/6.0/4.8
−30
7.1/5.9/4.8
−30
7.1/5.9/4.8
−30
dB
dB
Correlated Noise
Ratio
No signal,
correlated/
uncorrelated
Output Offset
−35
+35
−35
+35
−35
+35
LSB
Signal-to-Noise
Ratio (SNR)
fIN = 5 MHz at
−10 dBFS,
GAIN+ = 0 V
65.5
58.5
64
57
63.5
56.5
dBFS
fIN = 5 MHz at
−1 dBFS,
dBFS
GAIN+ = 1.6 V
Harmonic Distortion
Second
Harmonic
fIN = 5 MHz at
−10 dBFS,
GAIN+ = 0 V
−55
−67
−56
−61
−75
−52
−62
−50
−56
−75
−52
−58
−47
−55
−75
dBc
dBc
dBc
dBc
dBc
fIN = 5 MHz at
−1 dBFS,
GAIN+ = 1.6 V
Third Harmonic
fIN = 5 MHz at
−10 dBFS,
GAIN+ = 0 V
fIN = 5 MHz at
−1 dBFS,
GAIN+ = 1.6 V
Two-Tone IMD3
(2 × F1 − F2)
Distortion
fIN1 = 5.0 MHz at
−1 dBFS,
fIN2 = 5.01 MHz
at −21 dBFS,
GAIN+ = 1.6 V,
LNA gain =
21.3 dB
Channel-to-Channel fIN1 = 5.0 MHz at
−70
−65
0.3
−70
−65
0.3
−70
−65
0.3
dB
Crosstalk
−1 dBFS
Overrange
condition4
dB
Channel-to-Channel
Delay Variation
Full TGC path,
fIN = 5 MHz,
GAIN+ = 0 V to
1.6 V
Degrees
PGA GAIN
Differential
input to
21/24/27/30
21/24/27/30
21/24/27/30
dB
differential
output
Rev. B | Page 5 of 48
AD9273
AD9273-25
Typ
AD9273-40
Typ
AD9273-50
Typ
Parameter1
Conditions
Min
Max Min
Max Min
Max
Unit
GAIN ACCURACY
25°C
Gain Law Confor-
mance Error
0 V < GAIN+
< 0.16 V
1.5
1.5
1.5
dB
dB
dB
dB
0.16 V < GAIN+
< 1.44 V
−1.6
−1.6
+1.6
+1.6
−1.6
−1.6
+1.6
+1.6
−1.7
−1.7
+1.7
+1.7
1.44 V < GAIN+
< 1.6 V
−2.5
−2.5
−2.5
Linear Gain Error
GAIN+ = 0.8 V,
normalized for
ideal AAF loss
Channel-to-Channel 0.16 V < GAIN+
0.1
0.1
0.1
dB
Matching
< 1.44 V
GAIN CONTROL
INTERFACE
Normal Operating
Range
0
1.6
0
1.6
0
1.6
V
Gain Range
GAIN+ =
0 V to 1.6 V
42
42
42
dB
Scale Factor
28
28
28
dB/V
ns
Response Time
42 dB change
Single ended
Single ended
750
10
750
10
750
10
Gain+ Impedance
Gain− Impedance
CW DOPPLER MODE
Transconductance
MΩ
kΩ
70
70
70
Differential,
LNA gain =
15.6 dB/
5.4/7.3/10.9
5.4/7.3/10.9
5.4/7.3/10.9
mA/V
17.9 dB/
21.3 dB
Output Level Range
Differential,
CW Doppler
output pins
1.5
3.6
1.5
3.6
1.5
3.6
V
Input-Referred
Noise Voltage
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB,
2.6/2.1/1.6
2.6/2.1/1.6
2.6/2.1/1.6
nV/√Hz
RS = 0 Ω,
R
FB = ∞,
RL = 675 Ω
Input-Referred
Dynamic Range
LNA gain =
15.6 dB/
17.9 dB/
21.3 dB,
RS = 0 Ω,
RFB = ∞
160/159/158
160/159/158
160/159/158
dBFS/√Hz
Two-Tone IMD3
(2 × F1 − F2)
Distortion
fIN1 = 5.0 MHz at
−1 dBFS (FS at
−70
−70
−70
dBc
LNA input), fIN2
5.01 MHz at
=
−21 dBFS (FS at
LNA input), LNA
gain = 21.3 dB
Output DC Bias
Single ended,
per channel
2.4
2
2.4
2
2.4
2
mA
Maximum Output
Swing
Single ended,
per channel
mA p-p
POWER SUPPLY
AVDD1
1.7
2.7
1.7
1.8
3.0
1.8
158
1.9
3.6
1.9
1.7
2.7
1.7
1.8
3.0
1.8
186
1.9
3.6
1.9
1.7
2.7
1.7
1.8
3.0
1.8
223
1.9
3.6
1.9
V
AVDD2
V
DRVDD
V
IAVDD1
Full-channel
mode
mA
CW Doppler
mode with four
channels
32
32
32
mA
enabled
Rev. B | Page 6 of 48
AD9273
AD9273-25
Typ
AD9273-40
Typ
AD9273-50
Typ
Parameter1
Conditions
Min
Max Min
Max Min
Max
Unit
IAVDD2
Full-channel
mode
150
150
150
mA
CW Doppler
mode with four
channels
70
70
70
mA
enabled
IDRVDD
47
49
50
mA
Total Power
Dissipation
Includes output
drivers, full-
channel mode,
no signal
819
940
873
996
943
1072 mW
mW
CW Doppler
mode with four
channels
275
275
275
enabled
Power-Down
Dissipation
5
5
5
mW
Standby Power
Dissipation
148
158
170
mW
Power Supply
Rejection Ratio
(PSRR)
1.6
12
1.6
12
1.6
12
mV/V
ADC RESOLUTION
ADC REFERENCE
Bits
Output Voltage Error VREF = 1 V
20
20
20
mV
mV
Load Regulation
At 1.0 mA,
VREF = 1 V
2
6
2
6
2
6
Input Resistance
kΩ
1 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for a complete set of definitions and how these tests were completed.
2 SE = single ended.
3 AAF settings < 5 MHz are out of range and are not supported.
4 The overrange condition is specified as being 6 dB more than the full-scale input range.
Rev. B | Page 7 of 48
AD9273
DIGITAL SPECIFICATIONS
AVDD1 = 1.8 V, AVDD2 = 3.0 V, DRVDD = 1.8 V, 1.0 V internal ADC reference, fIN = 5 MHz, full temperature, unless otherwise noted.
Table 2.
Parameter1
Temperature
Min
Typ
Max
Unit
CLOCK INPUTS (CLK+, CLK−)
Logic Compliance
CMOS/LVDS/LVPECL
Differential Input Voltage2
Input Common-Mode Voltage
Input Resistance (Differential)
Input Capacitance
Full
Full
25°C
25°C
250
mV p-p
V
kΩ
pF
1.2
20
1.5
LOGIC INPUTS (PDWN, STBY, SCLK)
Logic 1 Voltage
Logic 0 Voltage
Input Resistance
Input Capacitance
Full
Full
25°C
25°C
1.2
1.2
3.6
0.3
V
V
kΩ
pF
30
0.5
LOGIC INPUT (CSB)
Logic 1 Voltage
Logic 0 Voltage
Full
Full
3.6
0.3
V
V
Input Resistance
Input Capacitance
25°C
25°C
70
0.5
kΩ
pF
LOGIC INPUT (SDIO)
Logic 1 Voltage
Logic 0 Voltage
Full
Full
1.2
0
DRVDD + 0.3
0.3
V
V
Input Resistance
Input Capacitance
25°C
25°C
30
2
kΩ
pF
LOGIC OUTPUT (SDIO)3
Logic 1 Voltage (IOH = 800 μA)
Logic 0 Voltage (IOL = 50 μA)
DIGITAL OUTPUTS (DOUTx+, DOUTx−) IN ANSI-644 MODE1
Logic Compliance
Full
Full
1.79
V
V
0.05
LVDS
Differential Output Voltage (VOD)
Output Offset Voltage (VOS)
Output Coding (Default)
Full
Full
247
1.125
454
1.375
mV
V
Offset binary
LVDS
DIGITAL OUTPUTS (DOUTx+, DOUTx−) WITH
LOW POWER, REDUCED-SIGNAL OPTION1
Logic Compliance
Differential Output Voltage (VOD)
Output Offset Voltage (VOS)
Output Coding (Default)
Full
Full
150
1.10
250
1.30
mV
V
Offset binary
1 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for a complete set of definitions and how these tests were completed.
2 Specified for LVDS and LVPECL only.
3 Specified for 13 SDIO pins sharing the same connection.
Rev. B | Page 8 of 48
AD9273
SWITCHING SPECIFICATIONS
AVDD1 = 1.8 V, AVDD2 = 3.0 V, DRVDD = 1.8 V, 1.0 V internal ADC reference, fIN = 5 MHz, full temperature, unless otherwise noted.
Table 3.
Parameter1
CLOCK2
Temp
Min
Typ
Max
Unit
Clock Rate
Full
Full
Full
10
50
MSPS
ns
ns
Clock Pulse Width High (tEH)
Clock Pulse Width Low (tEL)
OUTPUT PARAMETERS2, 3
Propagation Delay (tPD)
Rise Time (tR) (20% to 80%)
Fall Time (tF) (20% to 80%)
FCO Propagation Delay (tFCO
DCO Propagation Delay (tCPD
DCO to Data Delay (tDATA
DCO to FCO Delay (tFRAME
Data-to-Data Skew
10
10
Full
Full
Full
Full
Full
Full
Full
Full
(tSAMPLE/2) + 1.5
(tSAMPLE/2) + 1.5
(tSAMPLE/2) + 2.3
300
(tSAMPLE/2) + 3.1
(tSAMPLE/2) + 3.1
ns
ps
ps
ns
ns
ps
ps
ps
300
)
)
(tSAMPLE/2) + 2.3
tFCO + (tSAMPLE/24)
(tSAMPLE/24)
(tSAMPLE/24)
100
4
4
)
(tSAMPLE/24) − 300
(tSAMPLE/24) − 300
(tSAMPLE/24) + 300
(tSAMPLE/24) + 300
350
4
)
(tDATA-MAX − tDATA-MIN
)
<2
1
Wake-Up Time (Standby), GAIN+ = 0.8 V
Wake-Up Time (Power-Down)
Pipeline Latency
25°C
25°C
Full
ꢀs
ms
Clock cycles
8
APERTURE
<1
Aperture Uncertainty (Jitter)
25°C
ps rms
1 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for a complete set of definitions and how these tests were completed.
2 Can be adjusted via the SPI.
3 Measurements were made using a part soldered to FR-4 material.
4 tSAMPLE/24 is based on the number of bits divided by 2 because the delays are based on half duty cycles.
Rev. B | Page 9 of 48
AD9273
ADC TIMING DIAGRAMS
N – 1
AIN
N
tEH
tEL
CLK–
CLK+
tCPD
DCO–
DCO+
tFRAME
tFCO
FCO–
FCO+
tPD
tDATA
DOUTx–
MSB
N – 8
D10
N – 8
D9
N – 8
D8
N – 8
D7
N – 8
D6
N – 8
D5
N – 8
D4
N – 8
D3
N – 8
D2
N – 8
D1
N – 8
D0
N – 8
MSB
N – 7
D10
N – 7
DOUTx+
Figure 2. 12-Bit Data Serial Stream (Default)
N – 1
AIN
N
tEH
tEL
CLK–
CLK+
tCPD
DCO–
DCO+
tFRAME
tFCO
FCO–
FCO+
tPD
tDATA
DOUTx–
DOUTx+
D0
(LSB)
D1
N – 8
D2
N – 8
D3
N – 8
D4
N – 8
D5
N – 8
D6
N – 8
D7
N – 8
D8
N – 8
D9
N – 8
D10
N – 8
D11
(MSB)
Figure 3. 12-Bit Data Serial Stream, LSB First
Rev. B | Page 10 of 48
AD9273
ABSOLUTE MAXIMUM RATINGS
Table 4.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
With
Respect To
Parameter
Electrical
AVDD1
AVDD2
DRVDD
GND
AVDD2
AVDD2
AVDD1
Digital Outputs
(DOUTx+, DOUTx−,
DCO+, DCO−,
FCO+, FCO−)
CLK+, CLK−, GAIN+,
GAIN−
LI-x, LO-x, LOSW-x
CWDx−, CWDx+
PDWN, STBY, SCLK, CSB
RBIAS, VREF, SDIO
Environmental
Rating
GND
GND
GND
GND
AVDD1
DRVDD
DRVDD
GND
−0.3 V to +2.0 V
−0.3 V to +3.9 V
−0.3 V to +2.0 V
−0.3 V to +0.3 V
−2.0 V to +3.9 V
−2.0 V to +3.9 V
−2.0 V to +2.0 V
−0.3 V to +2.0 V
THERMAL IMPEDANCE
Table 5.
Airflow Velocity (m/sec)
1
θJA
θJB
N/A N/A °C/W
7.6 4.7 °C/W
N/A N/A °C/W
θJC
Unit
0.0
1.0
2.5
20.3
14.4
12.9
GND
−0.3 V to +3.9 V
1 θJA is for a 4-layer PCB with a solid ground plane (simulated). The exposed
pad is soldered to the PCB.
LG-x
GND
GND
GND
−0.3 V to +2.0 V
−0.3 V to +3.9 V
−0.3 V to +3.9 V
−0.3 V to +2.0 V
ESD CAUTION
Operating Temperature
Range (Ambient)
Storage Temperature
Range (Ambient)
Maximum Junction
Temperature
−40°C to +85°C
−65°C to +150°C
150°C
Lead Temperature
(Soldering, 10 sec)
300°C
Rev. B | Page 11 of 48
AD9273
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
PIN 1
INDICATOR
LI-E
LG-E
1
2
75 LI-D
74 LG-D
AVDD2
AVDD1
LO-F
3
AVDD2
73
72
71
70
AVDD1
LO-C
4
EXPOSED PADDLE, PIN 0
(BOTTOM OF PACKAGE)
5
LOSW-F
LI-F
6
LOSW-C
7
69 LI-C
AD9273
TOP VIEW
(Not to Scale)
LG-F
8
68 LG-C
67 AVDD2
AVDD2
AVDD1
LO-G
9
AVDD1
LO-B
10
11
66
65
LOSW-G 12
LI-G 13
64 LOSW-B
63 LI-B
LG-G 14
62 LG-B
AVDD2
AVDD1
LO-H
AVDD2
AVDD1
LO-A
15
16
17
61
60
59
LOSW-H 18
LI-H 19
58 LOSW-A
57 LI-A
LG-H 20
56 LG-A
21
22
23
AVDD2
AVDD1
CLK–
AVDD2
AVDD1
CSB
55
54
53
CLK+ 24
52 SDIO
51 SCLK
AVDD1 25
NOTES
1. THE EXPOSED PAD SHOULD BE TIED TO A QUIET ANALOG GROUND.
Figure 4. TQFP Pin Configuration
4
6
8
10
12
2
1
3
5
7
9
11
A
B
C
D
E
F
G
H
J
K
L
M
TOP VIEW
(Not to Scale)
Figure 5. BGA Pin Configuration
Rev. B | Page 12 of 48
AD9273
Table 6. Pin Function Descriptions
Pin No.
TQFP
0
N/A
BGA
Name
GND
GND
Description
N/A
Ground (the exposed paddle should be tied to a quiet analog ground)
Ground
B5, B6, B8, C5,
C6, C7, C8, D5,
D6, D7, D8, E1,
E5, E6, E7, E8,
E12, F2, F4, F6,
F7, F9, F11, G1,
G3, G5, G6, G7,
G8, G10, G12,
H2, H3, H4, H5,
H6, H7, H8, H9,
H10, H11, J2,
K1, K2, M1, M12
4, 10, 16, 22,
25, 50, 54, 60,
66, 72
3, 9, 15, 21, 55,
61, 67, 73, 86
F1, F3, F5, F8,
F10, F12, G2,
G4, G9, G11
B7, E2, E3, E4,
E9, E10, E11
AVDD1
AVDD2
1.8 V Analog Supply
3.0 V Analog Supply
26, 47
1
2
L1, L12
A1
B1
DRVDD
LI-E
LG-E
1.8 V Digital Output Driver Supply
LNA Analog Input for Channel E
LNA Ground for Channel E
5
6
7
8
C2
LO-F
LOSW-F
LI-F
LNA Analog Inverted Output for Channel F
LNA Analog Switched Output for Channel F
LNA Analog Input for Channel F
LNA Ground for Channel F
D2
A2
B2
LG-F
11
12
13
14
17
18
19
20
23
24
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
C3
LO-G
LOSW-G
LI-G
LG-G
LO-H
LOSW-H
LI-H
LG-H
CLK−
CLK+
DOUTH−
DOUTH+
DOUTG−
DOUTG+
DOUTF−
DOUTF+
DOUTE−
DOUTE+
DCO−
DCO+
FCO−
FCO+
DOUTD−
DOUTD+
DOUTC−
DOUTC+
DOUTB−
DOUTB+
LNA Analog Inverted Output for Channel G
LNA Analog Switched Output for Channel G
LNA Analog Input for Channel G
LNA Ground for Channel G
LNA Analog Inverted Output for Channel H
LNA Analog Switched Output for Channel H
LNA Analog Input for Channel H
LNA Ground for Channel H
Clock Input Complement
Clock Input True
ADC H Digital Output Complement
ADC H Digital Output True
ADC G Digital Output Complement
ADC G Digital Output True
ADC F Digital Output Complement
ADC F Digital Output True
ADC E Digital Output Complement
ADC E Digital Output True
Digital Clock Output Complement
Digital Clock Output True
Frame Clock Digital Output Complement
Frame Clock Digital Output True
ADC D Digital Output Complement
ADC D Digital Output True
D3
A3
B3
C4
D4
A4
B4
H1
J1
M2
L2
M3
L3
M4
L4
M5
L5
M6
L6
M7
L7
M8
L8
M9
L9
M10
L10
ADC C Digital Output Complement
ADC C Digital Output True
ADC B Digital Output Complement
ADC B Digital Output True
Rev. B | Page 13 of 48
AD9273
Pin No.
BGA
TQFP
45
46
48
49
51
52
53
56
57
58
59
62
63
64
65
68
69
70
71
74
75
76
77
78
79
80
81
82
83
84
85
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Name
DOUTA−
DOUTA+
STBY
PDWN
SCLK
SDIO
CSB
LG-A
LI-A
LOSW-A
LO-A
LG-B
LI-B
LOSW-B
LO-B
LG-C
LI-C
LOSW-C
LO-C
LG-D
Description
M11
L11
K11
J11
K12
J12
H12
B9
ADC A Digital Output Complement
ADC A Digital Output True
Standby Power-Down
Full Power-Down
Serial Clock
Serial Data Input/Output
Chip Select Bar
LNA Ground for Channel A
LNA Analog Input for Channel A
A9
D9
C9
LNA Analog Switched Output for Channel A
LNA Analog Inverted Output for Channel A
LNA Ground for Channel B
B10
A10
D10
C10
B11
A11
D11
C11
B12
A12
D12
C12
K10
J10
K9
J9
K8
J8
K7
J7
A8
A7
A6
LNA Analog Input for Channel B
LNA Analog Switched Output for Channel B
LNA Analog Inverted Output for Channel B
LNA Ground for Channel C
LNA Analog Input for Channel C
LNA Analog Switched Output for Channel C
LNA Analog Inverted Output for Channel C
LNA Ground for Channel D
LI-D
LOSW-D
LO-D
LNA Analog Input for Channel D
LNA Analog Switched Output for Channel D
LNA Analog Inverted Output for Channel D
CW Doppler Output Complement for Channel 0
CW Doppler Output True for Channel 0
CW Doppler Output Complement for Channel 1
CW Doppler Output True for Channel 1
CW Doppler Output Complement for Channel 2
CW Doppler Output True for Channel 2
CW Doppler Output Complement for Channel 3
CW Doppler Output True for Channel 3
Gain Control Voltage Input Complement
Gain Control Voltage Input True
CWD0−
CWD0+
CWD1−
CWD1+
CWD2−
CWD2+
CWD3−
CWD3+
GAIN−
GAIN+
RBIAS
External Resistor to Set the Internal ADC Core Bias Current
Voltage Reference Input/Output
A5
K6
J6
K5
J5
K4
J4
K3
VREF
CWD4−
CWD4+
CWD5−
CWD5+
CWD6−
CWD6+
CWD7−
CWD7+
LO-E
CW Doppler Output Complement for Channel 4
CW Doppler Output True for Channel 4
CW Doppler Output Complement for Channel 5
CW Doppler Output True for Channel 5
CW Doppler Output Complement for Channel 6
CW Doppler Output True for Channel 6
CW Doppler Output Complement for Channel 7
CW Doppler Output True for Channel 7
LNA Analog Inverted Output for Channel E
LNA Analog Switched Output for Channel E
J3
C1
D1
LOSW-E
Rev. B | Page 14 of 48
AD9273
TYPICAL PERFORMANCE CHARACTERISTICS
fSAMPLE = 40 MSPS, fIN = 5 MHz, RS = 50 Ω, LNA gain = 21.3 dB, LNA bias = mid-high, PGA gain = 24 dB, AAF LPF cutoff = fSAMPLE/3,
HPF = LPF cutoff/20.7 (default), GAIN− = 0.8 V
2.0
14
12
10
8
1.5
1.0
0.5
–40°C
+85°C
+25°C
0
6
–0.5
–1.0
–1.5
–2.0
4
2
0
0
0.2
0.4
0.6
0.8
GAIN+ (V)
1.0
1.2
1.4
1.6
GAIN ERROR (dB)
Figure 6. Gain Error vs. GAIN+ at Three Temperatures
Figure 9. Gain Error Histogram, GAIN+ = 1.44 V
20
18
16
14
12
10
8
25
20
15
10
6
4
5
0
2
0
–1.25 –1.00 –0.75 –0.50 –0.25
0
0.25 0.50 0.75 1.00 1.25
GAIN ERROR (dB)
CHANNEL-TO-CHANNEL GAIN MATCHING (dB)
Figure 7. Gain Error Histogram, GAIN+ = 0.16 V
Figure 10. Gain Match Histogram, GAIN+ = 0.3 V
25
20
15
10
14
12
10
8
6
4
5
0
2
0
–1.25 –1.00 –0.75 –0.50 –0.25
0
0.25 0.50 0.75 1.00 1.25
CHANNEL-TO-CHANNEL GAIN MATCHING (dB)
GAIN ERROR (dB)
Figure 11. Gain Match Histogram, GAIN+ = 1.3 V
Figure 8. Gain Error Histogram, GAIN+ = 0.8 V
Rev. B | Page 15 of 48
AD9273
–128
–129
–130
–131
–132
–133
–134
–135
–136
–137
–138
–139
500k
450k
400k
350k
300k
250k
200k
150k
100k
50k
LNA GAIN = 12×
LNA GAIN = 8×
LNA GAIN = 6×
0
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
–7 –6 –5 –4 –3 –2 –1
0
1
2
3
4
5
6
7
GAIN+ (V)
CODES
Figure 12. Output-Referred Noise Histogram, GAIN+ = 0.0 V
Figure 15. Short-Circuit, Output-Referred Noise vs. GAIN+
200k
65
60
55
50
45
40
180k
160k
140k
120k
100k
80k
60k
40k
20k
0
SNR
SINAD
–7 –6 –5 –4 –3 –2 –1
0
1
2
3
4
5
6
7
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
GAIN+ (V)
CODES
Figure 13. Output-Referred Noise Histogram, GAIN+ = 1.6 V
Figure 16. SNR/SINAD vs. GAIN+, AIN = −1.0 dBFS
3.0
0
–2
50MSPS
2.5
2.0
1.5
1.0
0.5
0
–4
40MSPS
–6
LNA GAIN = 15.6dB
LNA GAIN = 17.9dB
–8
–10
–12
–14
–16
–18
–20
25MSPS
LNA GAIN = 21.3dB
1
2
3
4
5
6
7
8
9
10
0
5
10
15
20
25
FREQUENCY (MHz)
FREQUENCY (MHz)
Figure 17. Antialiasing Filter (AAF) Pass-Band Response,
LPF Cutoff = 1 × (1/3) × fSAMPLE
Figure 14. Short-Circuit, Input-Referred Noise vs. Frequency,
PGA Gain = 30 dB, GAIN+ = 1.6 V
Rev. B | Page 16 of 48
AD9273
150
125
100
75
0
–20
–40
GAIN+ = 1.6V
GAIN+ = 0.8V
GAIN+ = 0V
GAIN+ = 0.8V
–60
GAIN+ = 0V
GAIN+ = 1.6V
50
–80
25
–100
–120
0
–40
–35
–30
–25
–20
–15
–10
–5
0
0
5
10
15
20
25
30
35
40
ADC OUTPUT LEVEL (dBFS)
FREQUENCY (MHz)
Figure 18. Antialiasing Filter (AAF) Group Delay Response
Figure 21. Second-Order Harmonic Distortion vs. ADC Output Level
0
0
–20
–40
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
GAIN+ = 0.8V
GAIN+ = 0V
–60
GAIN+ = 0.5V
–80
GAIN+ = 1.6V
GAIN+ = 1.6V
GAIN+ = 1.0V
–100
–120
0
2
4
6
8
10
12
14
16
–40
–35
–30
–25
–20
–15
–10
–5
0
INPUT FREQUENCY (MHz)
ADC OUTPUT LEVEL (dBFS)
Figure 19. Second-Order Harmonic Distortion vs. Input Frequency,
AIN = −1.0 dBFS
Figure 22. Third-Order Harmonic Distortion vs. ADC Output Level
0
–10
–20
–30
0
fIN1
= fIN2 + 0.01MHz
–10
–20
–30
–40
–50
–60
–70
–80
–90
A
1 = –1dBFS, A 2 = –21dBFS
IN
IN
–40
GAIN+ = 0.5V
GAIN+ = 1.6V
–50
5MHz
8MHz
–60
–70
GAIN+ = 1.0V
2.3MHz
–80
0
2
4
6
8
10
12
14
16
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
GAIN+ (V)
INPUT FREQUENCY (MHz)
Figure 20. Third-Order Harmonic Distortion vs. Input Frequency,
AIN = −1.0 dBFS
Figure 23. IMD3 vs. GAIN+
Rev. B | Page 17 of 48
AD9273
0
fIN1 = 5.00MHz, fIN2 = 5.01MHz
FUND2 LEVEL = FUND1 LEVEL – 20dB
–20
–40
–60
GAIN+ = 0.8V
GAIN+ = 1.6V
GAIN+ = 0V
–80
–100
–120
–40
–35
–30
–25
–20
–15
–10
–5
0
FUND1 LEVEL (dBFS)
Figure 24. IMD3 vs. Fundamental 1 Amplitude (FUND1) Level
Rev. B | Page 18 of 48
AD9273
EQUIVALENT CIRCUITS
AVDDx
V
AVDDx
CM
15kΩ
350Ω
30kΩ
LI-x,
LG-x
SDIO
Figure 25. Equivalent LNA Input Circuit
Figure 28. Equivalent SDIO Input Circuit
DRVDD
AVDDx
V
V
DOUTx–
DOUTx+
10Ω
V
V
LO-x,
LOSW-x
DRGND
Figure 26. Equivalent LNA Output Circuit
Figure 29. Equivalent Digital Output Circuit
10Ω
CLK+
10kΩ
10kΩ
1.25V
1kΩ
SCLK, PDWN,
OR STBY
10Ω
CLK–
30kΩ
Figure 27. Equivalent Clock Input Circuit
Figure 30. Equivalent SCLK, PDWN, or STBY Input Circuit
Rev. B | Page 19 of 48
AD9273
AVDDx
100Ω
RBIAS
AVDD2
50Ω
GAIN+
Figure 31. Equivalent RBIAS Circuit
Figure 34. Equivalent GAIN+ Input Circuit
AVDDx
70kΩ
1kΩ
0.8V
CSB
AVDD2
70kΩ
50Ω
GAIN–
Figure 32. Equivalent CSB Input Circuit
Figure 35. Equivalent GAIN− Input Circuit
10Ω
CWDx+,
CWDx–
+0.5V
VREF
6kΩ
Figure 36. Equivalent CWDx Output Circuit
Figure 33. Equivalent VREF Circuit
Rev. B | Page 20 of 48
AD9273
THEORY OF OPERATION
following the TGC amplifier, and then beam forming is
accomplished digitally.
ULTRASOUND
The primary application for the AD9273 is medical ultrasound.
Figure 37 shows a simplified block diagram of an ultrasound
system. A critical function of an ultrasound system is the time
gain control (TGC) compensation for physiological signal
attenuation. Because the attenuation of ultrasound signals is
exponential with respect to distance (time), a linear-in-dB VGA
is the optimal solution.
The ADC resolution of 12 bits with up to 50 MSPS sampling
satisfies the requirements of both general-purpose and high-
end systems.
Power conservation and low cost are two of the most important
factors in low-end and portable ultrasound machines, and the
AD9273 is designed to meet these criteria.
Key requirements in an ultrasound signal chain are very low noise,
active input termination, fast overload recovery, low power, and
differential drive to an ADC. Because ultrasound machines use
beam-forming techniques requiring a large binary-weighted
number of channels (for example, 32 to 512 channels), using the
lowest power at the lowest possible noise is of chief importance.
For additional information regarding ultrasound systems, refer
to “How Ultrasound System Considerations Influence Front-End
Component Choice,” Analog Dialogue, Volume 36, Number 3,
May–July 2002, and “The AD9271—A Revolutionary Solution
for Portable Ultrasound,” Analog Dialogue, Volume 41, Number 3,
July 2007.
Most modern machines use digital beam forming. In this
technique, the signal is converted to digital format immediately
Tx HV AMPs
BEAM-FORMER
CENTRAL CONTROL
Tx BEAM FORMER
MULTICHANNELS
AD9273
HV
Rx BEAM FORMER
(B AND F MODES)
MUX/
ADC
LNA
VGA
T/R
SWITCHES
DEMUX
AAF
CW
TRANSDUCER
ARRAY
128, 256, ETC.,
ELEMENTS
CW (ANALOG)
BEAM FORMER
IMAGE AND
MOTION
PROCESSING
(B MODE)
SPECTRAL
DOPPLER
PROCESSING
MODE
BIDIRECTIONAL
CABLE
COLOR
DOPPLER (PW)
PROCESSING
(F MODE)
AUDIO
OUTPUT
DISPLAY
Figure 37. Simplified Ultrasound System Block Diagram
Rev. B | Page 21 of 48
AD9273
R
R
LO-x
FB1
CWD[7:0]+
CWD[7:0]–
SWITCH
ARRAY
gm
C
FB
LOSW-x
FB2
T/R
SWITCH
C
S
LI-x
DOUTx+
DOUTx–
SERIAL
LVDS
ATTENUATOR
–42dB TO 0dB
PIPELINE
ADC
LNA
POSTAMP
FILTER
C
SH
LG-x
C
LG
15.6dB,
17.9dB,
21.3dB
21dB
24dB,
27dB,
30dB
GAIN
INTERPOLATOR
AD9273
Figure 38. Simplified Block Diagram of a Single Channel
The LNA supports differential output voltages as high as
CHANNEL OVERVIEW
4.4 V p-p with positive and negative excursions of 1.1 V from a
common-mode voltage of 1.5 V. The LNA differential gain sets
the maximum input signal before saturation. One of three gains
is set through the SPI. The corresponding full-scale input for
the gain settings of 6, 8, and 12 is 733 mV p-p, 550 mV p-p, and
367 mV p-p, respectively. Overload protection ensures quick
recovery time from large input voltages. Because the inputs are
capacitively coupled to a bias voltage near midsupply, very large
inputs can be handled without interacting with the ESD protection.
Each channel contains both a TGC signal path and a CW Doppler
signal path. Common to both signal paths, the LNA provides user-
adjustable input impedance termination. The CW Doppler path
includes a transconductance amplifier and a crosspoint switch.
The TGC path includes a differential X-AMP® VGA, an antialiasing
filter, and an ADC. Figure 38 shows a simplified block diagram
with external components.
The signal path is fully differential throughout to maximize signal
swing and reduce even-order distortion; however, the LNA is
designed to be driven from a single-ended signal source.
Low value feedback resistors and the current-driving capability
of the output stage allow the LNA to achieve a low input-referred
noise voltage of 1.26 nV/√Hz at a gain of 21.3 dB. This is achieved
with a current consumption of only 10 mA per channel (30 mW).
On-chip resistor matching results in precise single-ended gains,
which are critical for accurate impedance control. The use of a
fully differential topology and negative feedback minimizes
distortion. Low second-order harmonic distortion is particularly
important in second-order harmonic ultrasound imaging
applications. Differential signaling enables smaller swings at
each output, further reducing third-order distortion.
Low Noise Amplifier (LNA)
Good noise performance relies on a proprietary ultralow noise
LNA at the beginning of the signal chain, which minimizes the
noise contribution in the following VGA. Active impedance
control optimizes noise performance for applications that benefit
from input impedance matching.
A simplified schematic of the LNA is shown in Figure 39. LI-x is
capacitively coupled to the source. An on-chip bias generator
establishes dc input bias voltages of around 0.9 V and centers
the output common-mode levels at 1.5 V (AVDD2 divided by
2). A capacitor, CLG, of the same value as the input coupling
capacitor, CS, is connected from the LG-x pin to ground.
Recommendation
It is highly recommended that the LG-x pins form a Kelvin type
connection to the input or probe connection ground. Simply
connecting the LG pin to ground near the device may allow
differences in potential to be amplified through the LNA. This
generally shows up as a dc offset voltage that can vary from
channel to channel and part to part, depending on the
application and layout of the PCB (see Figure 38).
C
FB
R
FB1
FB2
V
+
O
R
V
–
O
LOSW-x
LO-x
V
CM
V
CM
T/R
SWITCH
C
S
LI-x
LG-x
C
SH
C
LG
Figure 39. Simplified LNA Schematic
Rev. B | Page 22 of 48
AD9273
1k
100
10
Active Impedance Matching
R
= 500Ω, R = 2kΩ
FB
S
The LNA consists of a single-ended voltage gain amplifier with
differential outputs and the negative output available externally.
For example, with a fixed gain of 8× (17.9 dB), an active input
termination is synthesized by connecting a feedback resistor
between the negative output pin, LO-x, and the positive input pin,
LI-x. This well-known technique is used for interfacing multiple
probe impedances to a single system. The input resistance is
shown in Equation 1.
R
R
= 200Ω, R = 800Ω
FB
S
S
= 100Ω, R = 400Ω, C = 20pF
FB SH
R
= 50Ω, R = 200Ω, C = 70pF
FB SH
S
RFB
RIN
=
(1)
A
(1 +
)
2
100k
1M
10M
100M
where A/2 is the single-ended gain or the gain from the LI-x
FREQUENCY (Hz)
inputs to the LO-x outputs, and RFB is the resulting impedance
of the RFB1 and RFB2 combination (see Figure 39).
Figure 40. RIN vs. Frequency for Various Values of RFB
(Effects of RS and CSH Are Also Shown)
Because the amplifier has a gain of 8× from its input to its
differential output, it is important to note that the gain A/2 is
the gain from Pin LI-x to Pin LO-x, and it is 6 dB less than the
gain of the amplifier, or 12.1 dB (4×). The input resistance is
reduced by an internal bias resistor of 15 kΩ in parallel with the
source resistance connected to Pin LI-x while Pin LG-x is ac
grounded. Equation 2 can be used to calculate the needed RFB
for a desired RIN, even for higher values of RIN.
Note that at the lowest value (50 Ω), RIN peaks at frequencies
greater than 10 MHz. This is due to the BW roll-off of the LNA,
as mentioned previously.
However, as can be seen for larger RIN values, parasitic capacitance
starts rolling off the signal BW before the LNA can produce
peaking. CSH further degrades the match; therefore, CSH should
not be used for values of RIN that are greater than 100 Ω. Table 7
lists the recommended values for RFB and CSH in terms of RIN.
RFB
(2)
RIN
=
||15 kΩ
CFB is needed in series with RFB because the dc levels at Pin LO-x
and Pin LI-x are unequal.
(1+ 3)
For example, to set RIN to 200 Ω, the value of RFB must be
1000 Ω. If the simplified equation (Equation 2) is used to
calculate RIN, the value is 188 Ω, resulting in a gain error less
than 0.6 dB. Some factors, such as the presence of a dynamic
source resistance, might influence the absolute gain accuracy
more significantly. At higher frequencies, the input capacitance
of the LNA needs to be considered. The user must determine
the level of matching accuracy and adjust RFB accordingly.
Table 7. Active Termination External Component Values
LNA Gain
(dB)
Minimum
CSH (pF)
RIN (Ω)
50
RFB (Ω)
200
BW (MHz)
15.6
17.9
21.3
15.6
17.9
21.3
15.6
17.9
21.3
90
57
69
88
57
69
88
72
72
72
50
250
70
50
350
50
100
100
100
200
200
200
400
500
700
800
1000
1400
30
20
10
N/A
N/A
N/A
The bandwidth (BW) of the LNA is greater than 100 MHz.
Ultimately, the BW of the LNA limits the accuracy of the
synthesized RIN. For RIN = RS up to about 200 Ω, the best match
is between 100 kHz and 10 MHz, where the lower frequency
limit is determined by the size of the ac-coupling capacitors,
and the upper limit is determined by the LNA BW. Furthermore,
the input capacitance and RS limit the BW at higher frequencies.
Figure 40 shows RIN vs. frequency for various values of RFB.
Rev. B | Page 23 of 48
AD9273
Figure 42 shows the relative noise figure performance. In this
graph, the input impedance was swept with RS to preserve the
match at each point. The noise figures for a source impedance of
50 ꢀ are 7.3 dB, 4.2 dB, and 2.8 dB for the resistive termination,
active termination, and unterminated configurations, respectively.
The noise figures for 200 ꢀ are 4.5 dB, 1.7 dB, and 1.0 dB,
respectively.
LNA Noise
The short-circuit noise voltage (input-referred noise) is an impor-
tant limit on system performance. The short-circuit input-referred
noise voltage for the LNA is 1.4 nV/√Hz at a gain of 21.3 dB,
including the VGA noise at a VGA postamp gain of 27 dB. These
measurements, which were taken without a feedback resistor,
provide the basis for calculating the input noise and noise figure
(NF) performance of the configurations shown in Figure 41.
UNTERMINATED
Figure 43 shows the noise figure as it relates to RS for various values
of RIN, which is helpful for design purposes.
R
IN
R
S
12.0
10.5
9.0
+
–
V
OUT
LI-x
RESISTIVE TERMINATION
R
IN
R
SHUNT TERMINATION
7.5
S
+
–
R
V
S
OUT
LI-x
6.0
4.5
3.0
1.5
0
UNTERMINATED
ACTIVE
TERMINATION
ACTIVE IMPEDANCE MATCH
R
FB
R
IN
R
S
+
–
V
OUT
LI-x
10
100
(Ω)
1k
R
S
R
FB
R
=
Figure 42. Noise Figure vs. RS for Shunt Termination,
Active Termination Matched, and Unterminated Inputs, VGAIN = 0.8 V
IN
1 + A/2
Figure 41. Input Configurations
12.0
Figure 42 and Figure 43 are simulations of noise figure vs. source
resistance (RS) results using these configurations and an input-
referred noise voltage of 6 nV/√Hz for the VGA. Unterminated
(RFB = ∞) operation exhibits the lowest equivalent input noise
and noise figure. Figure 43 shows the noise figure vs. RS rising at
low RS—where the LNA voltage noise is large compared with the
source noise—and at high RS due to the noise contribution from
RFB. The lowest NF is achieved when RS matches RIN.
UNTERMINATED
10.5
9.0
7.5
6.0
4.5
3.0
1.5
0
R
R
R
R
= 200Ω
= 100Ω
= 75Ω
IN
IN
IN
IN
= 50Ω
The main purpose of input impedance matching is to improve the
transient response of the system. With resistive termination, the
input noise increases due to the thermal noise of the matching
resistor and the increased contribution of the LNA’s input
voltage noise generator. With active impedance matching,
however, the contributions of both are smaller (by a factor of
1/(1 + LNA Gain)) than they would be for resistive termination.
10
100
1k
R
(Ω)
S
Figure 43. Noise Figure vs. RS for Various Fixed Values of RIN
,
Active Termination Matched Inputs, VGAIN = 0.8 V
Rev. B | Page 24 of 48
AD9273
INPUT OVERDRIVE
CW DOPPLER OPERATION
Excellent overload behavior is of primary importance in
ultrasound. Both the LNA and VGA have built-in overdrive
protection and quickly recover after an overload event.
Modern ultrasound machines used for medical applications
employ a 2N binary array of receivers for beam forming, with
typical array sizes of 16 or 32 receiver channels phase-shifted
and summed together to extract coherent information. When
used in multiples, the desired signals from each channel can be
summed to yield a larger signal (increased by a factor N, where
N is the number of channels), and the noise is increased by the
square root of the number of channels. This technique enhances
the signal-to-noise performance of the machine. The critical
elements in a beam-former design are the means to align the
incoming signals in the time domain and the means to sum the
individual signals into a composite whole.
Input Overload Protection
As with any amplifier, voltage clamping prior to the inputs is
highly recommended if the application is subject to high
transient voltages.
In Figure 44, a simplified ultrasound transducer interface is
shown. A common transducer element serves the dual functions
of transmitting and receiving ultrasound energy. During the
transmitting phase, high voltage pulses are applied to the ceramic
elements. A typical transmit/receive (T/R) switch can consist of
four high voltage diodes in a bridge configuration. Although the
diodes ideally block transmit pulses from the sensitive receiver
input, diode characteristics are not ideal, and the resulting leakage
transients imposed on the LI-x inputs can be problematic.
Beam forming, as applied to medical ultrasound, is defined as the
phase alignment and summation of signals that are generated
from a common source but received at different times by a
multielement ultrasound transducer. Beam forming has two
functions: it imparts directivity to the transducer, enhancing its
gain, and it defines a focal point within the body from which the
location of the returning echo is derived.
Because ultrasound is a pulse system and time-of-flight is used to
determine depth, quick recovery from input overloads is essential.
Overload can occur in the preamp and the VGA. Immediately
following a transmit pulse, the typical VGA gains are low, and
the LNA is subject to overload from T/R switch leakage. With
increasing gain, the VGA can become overloaded due to strong
echoes that occur near field echoes and acoustically dense materials,
such as bone.
The AD9273 includes the front-end components needed to
implement analog beam forming for CW Doppler operation.
These components allow CW channels with similar phases to be
coherently combined before phase alignment and down mixing,
thus reducing the number of delay lines or adjustable phase shifters/
down mixers (AD8333 or AD8339) required. Next, if delay lines
are used, the phase alignment is performed, and then the channels
are coherently summed and down converted by a dynamic range
I/Q demodulator. Alternatively, if phase shifters/down mixers,
such as the AD8333 and AD8339, are used, phase alignment
and downconversion are done before coherently summing all
channels into I/Q signals. In either case, the resultant I and Q
signals are filtered and sampled by two high resolution ADCs,
and the sampled signals are processed to extract the relevant
Doppler information.
Figure 44 illustrates an external overload protection scheme. A
pair of back-to-back signal diodes is installed prior to installing the
ac-coupling capacitors. Keep in mind that all diodes shown in
this example are prone to exhibiting some amount of shot noise.
Many types of diodes are available for achieving the desired noise
performance. The configuration shown in Figure 44 tends to add
2 nV/√Hz of input-referred noise. Decreasing the 5 kΩ resistor
and increasing the 2 kΩ resistor may improve noise contribution,
depending on the application. With the diodes shown in Figure 44,
clamping levels of 0.5 V or less significantly enhance the overload
performance of the system.
Alternately, the LNA of the AD9273 can directly drive the AD8333
or AD8339 without the crosspoint switch. The LO-x pins present
the inverting LNA output, and the LOSW-x pins can be configured
via Register 0x2C (see Table 17) to connect to the noninverting
output to provide a differential output of the LNA. The LNA output
full-scale voltage of the AD9273 is 4.4 V p-p, and the input full-
scale voltage is 2.7 V p-p. If no attenuation is provided between
the LNA output and the demodulator, the LNA input full-scale
voltage must be limited.
+5V
Tx
DRIVER
5kΩ
HV
AD9273
10nF
LNA
2kΩ
10nF
5kΩ
TRANSDUCER
–5V
Figure 44. Input Overload Protection
Rev. B | Page 25 of 48
AD9273
AD9273
gm
LNA
LNA
gm
SWITCH
ARRAY
8 × CHANNEL
LNA
gm
gm
AD8333
600µH
600µH
LNA
2.5V
2.5V
700Ω
700Ω
600µH
600µH
AD8333
AD9273
gm
600µH
600µH
700Ω
700Ω
2.5V
2.5V
LNA
LNA
600µH
600µH
gm
SWITCH
ARRAY
I
8 × CHANNEL
LNA
16-BIT
ADC
gm
gm
Q
16-BIT
ADC
LNA
Figure 45. Typical Connection Interface with the AD8333 or AD8339 using the CWDx Outputs
2.5V
AD9273
5kΩ
5kΩ
5kΩ
5kΩ
1nF
AD8339
LO-A
500Ω
500Ω
500Ω
500Ω
LNA
LOSW-A
1nF
1nF
2.5V
LOS-B
LNA
LOSW-B
1nF
2.5V
5kΩ
5kΩ
1nF
1nF
AD8339
LO-H
500Ω
500Ω
LNA
I
LOSW-H
16-BIT
ADC
Q
16-BIT
ADC
Figure 46. Typical Connection Interface with the AD8333 or AD8339 using the LO-x and LOSW-x Outputs
Rev. B | Page 26 of 48
AD9273
The maximum gain required is determined by
Crosspoint Switch
Each LNA is followed by a transconductance amp for voltage-
to-current conversion. Currents can be routed to one of eight
pairs of differential outputs or to 16 single-ended outputs for
summing. Each CWD output pin sinks 2.4 mA dc current, and
the signal has a full-scale current of 2 mA for each channel
selected by the crosspoint switch. For example, if four channels
are summed on one CWD output, the output sinks 9.6 mA dc
and has a full-scale current output of 8 mA.
(ADC Noise Floor/VGA Input Noise Floor) + Margin =
20 log(224/5.4) + 11 dB = 43 dB
The minimum gain required is determined by
(ADC Input FS/VGA Input FS) + Margin =
20 log(2/0.55) – 10 dB = 3 dB
Therefore, 42 dB of gain range for a 12-bit, 40 MSPS ADC with
15 MHz of bandwidth should suffice in achieving the dynamic
range required for most of today’s ultrasound systems.
The maximum number of channels combined must be considered
when setting the load impedance for current-to-voltage conversion
to ensure that the full-scale swing and common-mode voltage
are within the operating limits of the AD9273. When interfacing
to the AD8339, a common-mode voltage of 2.5 V and a full-scale
swing of 2.8 V p-p are desired. This can be accomplished by
connecting an inductor between each CWD output and a 2.5 V
supply, and then connecting either a single-ended or differential
load resistance to the CWDx outputs. The value of resistance
should be calculated based on the maximum number of channels
that can be combined.
The system gain is distributed as listed in Table 8.
Table 8. Channel Gain Distribution
Section
Nominal Gain (dB)
LNA
15.6/17.9/21.3
Attenuator
VGA Amp
Filter
−42 to 0
21/24/27/30
0
0
ADC
The linear-in-dB gain (law conformance) range of the TGC path
is 42 dB. The slope of the gain control interface is 28 dB/V, and
the gain control range is −0.8 V to +0.8 V. Equation 3 is the
expression for the differential voltage VGAIN, and Equation 4 is
the expression for the channel gain.
CWDx outputs are required under full-scale swing to be
greater than 1.5 V and less than AVDD2 (3.0 V supply).
TGC OPERATION
The TGC signal path is fully differential throughout to maximize
signal swing and reduce even-order distortion; however, the LNAs
are designed to be driven from a single-ended signal source. Gain
values are referenced from the single-ended LNA input to the
differential ADC input. A simple exercise in understanding the
maximum and minimum gain requirements is shown in Figure 47.
V
GAIN (V) = GAIN(+)− GAIN(−)
(3)
dB
V
Gain (dB) = 28
VGAIN + ICPT
(4)
where ICPT is the intercept point of the TGC gain.
In its default condition, the LNA has a gain of 21.3 dB (12×) and
the VGA postamp gain is 24 dB if the voltage on the GAIN+ pin is
0 V and the voltage on the GAIN− pin is 0.8 V (42 dB attenuation).
This gives rise to a total gain (or ICPT) of 3.6 dB through the
TGC path if the LNA input is unmatched, or of −2.4 dB if the
LNA is matched to 50 Ω (RFB = 350 Ω). If the voltage on the
GAIN+ pin is 1.6 V and the voltage on the GAIN− pin is 0.8 V
(0 dB attenuation), however, the VGA gain is 24 dB. This results
in a total gain of 45 dB through the TGC path if the LNA input is
unmatched, or in a total gain of 39 dB if the LNA input is matched.
ADC FS (2V p-p)
MINIMUM GAIN
~10dB MARGIN
LNA FS
(0.55V p-p SE)
70dB
ADC
91dB
>11dB MARGIN
ADC NOISE FLOOR
(224µV rms)
LNA
MAXIMUM GAIN
LNA INPUT-REFERRED
NOISE FLOOR
(5.4µV rms) @ AAF BW = 15MHz
LNA + VGA NOISE = 1.4nV/ Hz
VGA GAIN RANGE > 42dB
MAX CHANNEL GAIN > 48dB
Figure 47. Gain Requirements of TGC Operation for a 12-Bit, 40 MSPS ADC
Each LNA output is dc-coupled to a VGA input. The VGA consists
of an attenuator with a range of −42 dB to 0 dB followed by an
amplifier with 21 dB, 24 dB, 27 dB, or 30 dB of gain. The X-AMP
gain-interpolation technique results in low gain error and uniform
bandwidth, and differential signal paths minimize distortion.
Rev. B | Page 27 of 48
AD9273
Table 9. Sensitivity and Dynamic Range of Trade-Offs1, 2, 3
LNA
Channel
Typical Output Dynamic Range
Gain
Input-Referred
Full-Scale Input Noise Voltage
VGA
Input-Referred Noise6
@
GAIN+ = 1.6 V (nV/√Hz)
(V/V) (dB) (V p-p)
(nV/√Hz)
Postamp Gain (dB) GAIN+ = 0 V4
GAIN+ = 1.6 V5
62.3
59.7
57.0
6
15.6 0.733
17.9 0.550
21.3 0.367
1.6
21
24
27
30
21
24
27
30
21
24
27
30
65.9
64.1
61.8
59.2
65.9
64.1
61.8
59.2
65.9
64.1
61.8
59.2
1.98
1.91
1.87
1.85
1.66
1.61
1.58
1.57
1.35
1.32
1.31
1.30
54.1
8
1.42
1.26
61.6
58.9
56.2
53.3
12
60.1
57.3
54.4
51.5
1 LNA: output full scale = 4.4 V p-p differential.
2 Filter: loss ~ 1 dB, NBW = 13.3 MHz, GAIN− = 0.8 V.
3 ADC: 40 MSPS, 70 dB SNR, 2 V p-p full-scale input.
4 Output dynamic range at minimum VGA gain (VGA dominated).
5 Output dynamic range at maximum VGA gain (LNA dominated).
6 Channel noise at maximum VGA gain.
Table 9 demonstrates the sensitivity and dynamic range of
trade-offs that can be achieved relative to various LNA and
VGA gain settings.
GAIN+ and GAIN− pins. The LNA has three limitations, or full-
scale settings, that can be applied through the SPI. Similarly, the
VGA has four postamp gain settings that can be applied through
the SPI. The voltage applied to the GAIN pins determines
which amplifier (the LNA or VGA) saturates first. The maximum
signal input level that can be applied as a function of voltage on
the GAIN pins for the selectable gain options of the SPI is shown
in Figure 48 to Figure 50.
For example, when the VGA is set for the minimum gain voltage,
the TGC path is dominated by VGA noise and achieves the
maximum output SNR. However, as the postamp gain options
are increased, the input-referred noise is reduced and the SNR
is degraded.
0.40
If the VGA is set for the maximum gain voltage, the TGC path
is dominated by LNA noise and achieves the lowest input-
referred noise, but with degraded output SNR. The higher the
TGC (LNA + VGC) gain, the lower the output SNR. As the
postamp gain is increased, the input-referred noise is reduced.
0.35
PGA GAIN = 21dB
0.30
PGA GAIN = 24dB
0.25
PGA GAIN = 27dB
0.20
At low gains, the VGA should limit the system noise perfor-
mance (SNR); at high gains, the noise is defined by the source and
the LNA. The maximum voltage swing is bound by the full-
scale peak-to-peak ADC input voltage (2 V p-p).
0.15
PGA GAIN = 30dB
0.10
0.05
0
Both the LNA and VGA have full-scale limitations within each
section of the TGC path. These limitations are dependent on the
gain setting of each function block and on the voltage applied to the
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
GAIN+ (V)
Figure 48. LNA with 15.6 dB Gain Setting/VGA Full-Scale Limitations
Rev. B | Page 28 of 48
AD9273
0.6
0.5
0.4
0.3
0.2
0.1
per side is 180 Ω nominally for a total differential resistance of
360 Ω. The ladder is driven by a fully differential input signal from
the LNA. LNA outputs are dc-coupled to avoid external decoupling
capacitors. The common-mode voltage of the attenuator and the
VGA is controlled by an amplifier that uses the same midsupply
voltage derived in the LNA, permitting dc coupling of the LNA
to the VGA without introducing large offsets due to common-
mode differences. However, any offset from the LNA becomes
amplified as the gain increases, producing an exponentially
increasing VGA output offset.
PGA GAIN = 21dB
PGA GAIN = 24dB
PGA GAIN = 27dB
The input stages of the X-AMP are distributed along the ladder,
and a biasing interpolator, controlled by the gain interface, deter-
mines the input tap point. With overlapping bias currents, signals
from successive taps merge to provide a smooth attenuation range
from −42 dB to 0 dB. This circuit technique results in linear-in-dB
gain law conformance and low distortion levels—only deviating
0.5 dB or less from the ideal. The gain slope is monotonic with
respect to the control voltage and is stable with variations in
process, temperature, and supply.
PGA GAIN = 30dB
0.4 0.6
0
0
0.2
0.8
1.0
1.2
1.4
1.6
GAIN+ (V)
Figure 49. LNA with 17.9 dB Gain Setting/VGA Full-Scale Limitations
0.9
0.8
PGA GAIN = 21dB
0.7
0.6
The X-AMP inputs are part of a programmable gain feedback
amplifier that completes the VGA. Its bandwidth is approximately
100 MHz. The input stage is designed to reduce feedthrough to
the output and to ensure excellent frequency response uniformity
across the gain setting.
PGA GAIN = 24dB
0.5
0.4
0.3
0.2
Gain Control
PGA GAIN = 27dB
0.1
The gain control interface, GAIN , is a differential input. VGAIN
varies the gain of all VGAs through the interpolator by selecting
the appropriate input stages connected to the input attenuator.
For GAIN− at 0.8 V, the nominal GAIN+ range for 28 dB/V is
0 V to 1.6 V, with the best gain linearity from about 0.16 V to
1.44 V, where the error is typically less than 0.5 dB. For
GAIN+ voltages greater than 1.44 V and less than 0.16 V, the
error increases. The value of GAIN+ can exceed the supply
voltage by 1 V without gain foldover.
PGA GAIN = 30dB
0
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
GAIN+ (V)
Figure 50. LNA with 21.3 dB Gain Setting/VGA Full-Scale Limitations
Variable Gain Amplifier
The differential X-AMP VGA provides precise input attenuation
and interpolation. It has a low input-referred noise of 6 nV/√Hz
and excellent gain linearity. A simplified block diagram is shown in
Figure 51.
Gain control response time is less than 750 ns to settle within 10%
of the final value for a change from minimum to maximum gain.
GAIN±
GAIN INTERPOLATOR
POSTAMP
+
There are two ways in which the GAIN+ and GAIN− pins can
be interfaced. With the single-ended method, a Kelvin type of
connection to ground can be used as shown in Figure 52. For
driving multiple devices, it is preferable to use the differential
method shown in Figure 53. In either method, the GAIN+ and
GAIN− pins should be dc-coupled and driven to accommodate
a 1.6 V full-scale input.
g
m
3dB
VIP
VIN
AD9273
100Ω
0V TO 1.6V DC
GAIN+
GAIN–
–
POSTAMP
50Ω
0.01µF
Figure 51. Simplified VGA Schematic
KELVIN
CONNECTION
0.01µF
The input of the VGA is a 14-stage differential resistor ladder with
3.5 dB per tap. The resulting total gain range is 42 dB, which
allows for range loss at the endpoints. The effective input resistance
Figure 52. Single-Ended GAIN Pins Configuration
Rev. B | Page 29 of 48
AD9273
499Ω
AVDD2
31.3kΩ
50Ω
The antialaising filter is a combination of a single-pole high-
pass filter and a second-order low-pass filter. The high-pass
filter can be configured at a ratio of the low-pass filter cutoff.
This is selectable through the SPI.
±0.4VDC AT
0.8V CM
AD9273
499Ω
100Ω
0.01µF
100Ω
GAIN+
±0.8V DC
0.8V CM
AD8138
523Ω
GAIN–
10kΩ
The filter uses on-chip tuning to trim the capacitors and in turn
set the desired cutoff frequency and reduce variations. The
default −3 dB low-pass filter cutoff is 1/3 or 1/4.5 the ADC
sample clock rate. The cutoff can be scaled to 0.7, 0.8, 0.9, 1, 1.1,
1.2, or 1.3 times this frequency through the SPI. The cutoff
tolerance is maintained from 8 MHz to 18 MHz.
4kΩ
±0.4VDC AT
0.8V CM
0.01µF
499Ω
Figure 53. Differential GAIN Pins Configuration
VGA Noise
In a typical application, a VGA compresses a wide dynamic
range input signal to within the input span of an ADC. The
input-referred noise of the LNA limits the minimum resolvable
input signal, whereas the output-referred noise, which depends
primarily on the VGA, limits the maximum instantaneous
dynamic range that can be processed at any one particular gain
control voltage. This latter limit is set in accordance with the
total noise floor of the ADC.
C
30C
4kΩ
10kΩ/n
4kΩ
2kΩ
4C
2kΩ
30C
C
Output-referred noise as a function of GAIN+ is shown in Figure 15
for the short-circuit input conditions. The input noise voltage is
simply equal to the output noise divided by the measured gain
at each point in the control range.
C = 0.8pF TO 5.1pF
n = 0 TO 7
4kΩ
Figure 54. Simplified Filter Schematic
Tuning is normally off to avoid changing the capacitor settings
during critical times. The tuning circuit is enabled and disabled
through the SPI. Initializing the tuning of the filter must be
performed after initial power-up and after reprogramming the
filter cutoff scaling or ADC sample rate. Occasional retuning
during an idle time is recommended to compensate for
temperature drift.
The output-referred noise is a flat 90 nV/√Hz (postamp gain =
24 dB) over most of the gain range because it is dominated by
the fixed output-referred noise of the VGA. At the high end of
the gain control range, the noise of the LNA and of the source
prevail. The input-referred noise reaches its minimum value
near the maximum gain control voltage, where the input-
referred contribution of the VGA is miniscule.
There is a total of eight SPI-programmable settings that allow the
user to vary the high-pass filter cutoff frequency as a function
of the low-pass cutoff frequency. Two examples are shown in
Table 10: one is for an 8 MHz low-pass cutoff frequency, and the
other is for an 18 MHz low-pass cutoff frequency. In both cases,
as the ratio decreases, the amount of rejection on the low-end
frequencies increases. Therefore, making the entire AAF
frequency pass band narrow can reduce low frequency noise or
maximize dynamic range for harmonic processing.
At lower gains, the input-referred noise, and therefore the noise
figure, increases as the gain decreases. The instantaneous
dynamic range of the system is not lost, however, because the
input capacity increases as the input-referred noise increases.
The contribution of the ADC noise floor has the same
dependence. The important relationship is the magnitude of the
VGA output noise floor relative to that of the ADC.
Gain control noise is a concern in very low noise applications.
Thermal noise in the gain control interface can modulate the
channel gain. The resultant noise is proportional to the output
signal level and is usually evident only when a large signal is
present. The gain interface includes an on-chip noise filter, which
significantly reduces this effect at frequencies greater than 5 MHz.
Care should be taken to minimize noise impinging at the GAIN
inputs. An external RC filter can be used to remove VGAIN source
noise. The filter bandwidth should be sufficient to accommodate
the desired control bandwidth.
Table 10. SPI-Selectable High-Pass Filter Cutoff Options
High-Pass Cutoff
Low-Pass Cutoff
SPI Setting Ratio1 = 8 MHz
Low-Pass Cutoff
= 18 MHz
0
1
2
3
4
5
6
7
20.65
11.45
7.92
6.04
4.88
4.10
3.52
3.09
387 kHz
698 kHz
872 kHz
1.571 MHz
2.273 MHz
2.978 MHz
3.685 MHz
4.394 MHz
5.107 MHz
5.822 MHz
1.010 MHz
1.323 MHz
1.638 MHz
1.953 MHz
2.270 MHz
2.587 MHz
Antialiasing Filter
The filter that the signal reaches prior to the ADC is used to
reject dc signals and to band limit the signal for antialiasing.
Figure 54 shows the architecture of the filter.
1 Ratio = low-pass filter cutoff frequency/high-pass filter cutoff frequency.
Rev. B | Page 30 of 48
AD9273
3.3V
ADC
AD951x/AD952x
FAMILY
*
50Ω
VFAC3
OUT
0.1µF
0.1µF
0.1µF
The AD9273 uses a pipelined ADC architecture. The quantized
output from each stage is combined into a 12-bit result in the
digital correction logic. The pipelined architecture permits the
first stage to operate on a new input sample and the remaining
stages to operate on preceding samples. Sampling occurs on the
rising edge of the clock.
CLK
CLK+
ADC
AD9273
100Ω
LVDS DRIVER
CLK
0.1µF
CLK–
*
50Ω RESISTOR IS OPTIONAL.
The output staging block aligns the data, corrects errors, and
passes the data to the output buffers. The data is then serialized
and aligned to the frame and output clocks.
Figure 57. Differential LVDS Sample Clock
In some applications, it is acceptable to drive the sample clock
inputs with a single-ended CMOS signal. In such applications,
CLK+ should be driven directly from a CMOS gate, and the
CLK− pin should be bypassed to ground with a 0.1 μF capacitor
in parallel with a 39 kΩ resistor (see Figure 58). Although the
CLK+ input circuit supply is AVDDx (1.8 V), this input is
designed to withstand input voltages of up to 3.3 V, making the
selection of the drive logic voltage very flexible.
CLOCK INPUT CONSIDERATIONS
For optimum performance, the AD9273 sample clock inputs
(CLK+ and CLK−) should be clocked with a differential signal.
This signal is typically ac-coupled into the CLK+ and CLK− pins
via a transformer or using capacitors. These pins are biased
internally and require no additional bias.
3.3V
Figure 55 shows the preferred method for clocking the AD9273.
A low jitter clock source, such as the Valpey Fisher oscillator
VFAC3-BHL-50MHz, is converted from single ended to
differential using an RF transformer. The back-to-back Schottky
diodes across the secondary transformer limit clock excursions
into the AD9273 to approximately 0.8 V p-p differential. This
helps prevent the large voltage swings of the clock from feeding
through to other portions of the AD9273, and it preserves the
fast rise and fall times of the signal, which are critical to low
jitter performance.
AD951x/AD952x
FAMILY
0.1µF
VFAC3
CLK
CMOS DRIVER
CLK
OUT
OPTIONAL
0.1µF
*
50Ω
100Ω
CLK+
ADC
AD9273
0.1µF
CLK–
0.1µF
39kΩ
*
50Ω RESISTOR IS OPTIONAL.
Figure 58. Single-Ended 1.8 V CMOS Sample Clock
3.3V
3.3V
AD951x/AD952x
FAMILY
MINI-CIRCUITS
ADT1-1WT, 1:1Z
0.1µF
VFAC3
OUT
CLK
0.1µF
0.1µF
OPTIONAL
XFMR
0.1µF
0.1µF
*
50Ω
OUT
CLK+
100Ω
CLK+
CMOS DRIVER
CLK
100Ω
ADC
50Ω
0.1µF
AD9273
VFAC3
ADC
AD9273
CLK–
0.1µF
SCHOTTKY
DIODES:
0.1µF
CLK–
HSM2812
Figure 55. Transformer-Coupled Differential Clock
*
50Ω RESISTOR IS OPTIONAL.
If a low jitter clock is available, another option is to ac-couple a
differential PECL signal to the sample clock input pins as shown
in Figure 56. The AD951x/AD952x family of clock drivers offers
excellent jitter performance.
Figure 59. Single-Ended 3.3 V CMOS Sample Clock
Clock Duty Cycle Considerations
Typical high speed ADCs use both clock edges to generate a
variety of internal timing signals. As a result, these ADCs may
be sensitive to the clock duty cycle. Commonly, a 5% tolerance is
required on the clock duty cycle to maintain dynamic performance
characteristics. The AD9273 contains a duty cycle stabilizer (DCS)
that retimes the nonsampling edge, providing an internal clock
signal with a nominal 50% duty cycle. This allows a wide range
of clock input duty cycles without affecting the performance of
the AD9273. When the DCS is on, noise and distortion perfor-
mance are nearly flat for a wide range of duty cycles. However,
some applications may require the DCS function to be off. If so,
keep in mind that the dynamic range performance can be affected
when operated in this mode. See Table 17 for more details on
using this feature.
3.3V
AD951x/AD952x
*
50Ω
FAMILY
VFAC3
0.1µF
0.1µF
0.1µF
OUT
CLK
PECL DRIVER
CLK
CLK+
ADC
AD9273
100Ω
0.1µF
CLK–
240Ω
240Ω
*
50Ω RESISTOR IS OPTIONAL.
Figure 56. Differential PECL Sample Clock
Rev. B | Page 31 of 48
AD9273
250
200
150
100
50
The duty cycle stabilizer uses a delay-locked loop (DLL) to
create the nonsampling edge. As a result, any changes to the
sampling frequency require approximately eight clock cycles
to allow the DLL to acquire and lock to the new rate.
I
, 50MSPS SPEED GRADE
AVDD1
I
, 40MSPS SPEED GRADE
AVDD1
Clock Jitter Considerations
High speed, high resolution ADCs are sensitive to the quality of the
clock input. The degradation in SNR at a given input frequency (fA)
due only to aperture jitter (tJ) can be calculated by
I
, 25MSPS SPEED GRADE
AVDD1
SNR Degradation = 20 × log 10[1/2 × π × fA × tJ]
I
DRVDD
In this equation, the rms aperture jitter represents the root mean
square of all jitter sources, including the clock input, analog input
signal, and ADC aperture jitter. IF undersampling applications
are particularly sensitive to jitter (see Figure 60).
0
0
10
20
30
40
50
SAMPLING FREQUENCY (MSPS)
Figure 61. Supply Current vs. fSAMPLE for fIN = 5 MHz
The clock input should be treated as an analog signal in cases
where aperture jitter may affect the dynamic range of the AD9273.
Power supplies for clock drivers should be separated from the
ADC output driver supplies to avoid modulating the clock signal
with digital noise. Low jitter, crystal-controlled oscillators make
the best clock sources, such as the Valpey Fisher VFAC3 series.
If the clock is generated from another type of source (by gating,
dividing, or other methods), it should be retimed by the
original clock during the last step.
120
115
110
105
100
95
50MSPS SPEED GRADE
40MSPS SPEED GRADE
25MSPS SPEED GRADE
90
Refer to the AN-501 Application Note and the AN-756
Application Note for more in-depth information about how
jitter performance relates to ADCs (visit www.analog.com).
85
80
130
0
10
20
30
40
50
RMS CLOCK JITTER REQUIREMENT
120
110
SAMPLING FREQUENCY (MSPS)
Figure 62. Power per Channel vs. fSAMPLE for fIN = 5 MHz
16 BITS
100
90
80
70
60
50
40
30
The AD9273 features scalable LNA bias currents (see Register 0x12
in Table 17). The default LNA bias current settings are high.
Figure 63 shows the typical reduction of AVDD2 current with
each bias setting. It is also recommended to adjust the LNA
offset using Register 0x10 (see Table 17) when the LNA bias
setting is low.
14 BITS
12 BITS
10 BITS
8 BITS
0.125ps
0.25ps
0.5ps
1.0ps
2.0ps
HIGH
1
10
100
1000
ANALOG INPUT FREQUENCY (MHz)
MID-HIGH
Figure 60. Ideal SNR vs. Analog Input Frequency and Jitter
Power Dissipation and Power-Down Mode
As shown in Figure 62, the power dissipated by the AD9273 is
proportional to its sample rate. The digital power dissipation
does not vary much because it is determined primarily by the
DRVDD supply and bias current of the LVDS output drivers.
MID-LOW
LOW
0
20
40
60
80
100
120
140
160
180
TOTAL AVDD2 CURRENT (mA)
Figure 63. AVDD2 Current at Different LNA Bias Settings, AD9273-40
Rev. B | Page 32 of 48
AD9273
By asserting the PDWN pin high, the AD9273 is placed into
power-down mode. In this state, the device typically dissipates
2 mW. During power-down, the LVDS output drivers are placed
into a high impedance state. The AD9273 returns to normal
operating mode when the PDWN pin is pulled low. This pin is
both 1.8 V and 3.3 V tolerant.
The AD9273 LVDS outputs facilitate interfacing with LVDS
receivers in custom ASICs and FPGAs that have LVDS capability
for superior switching performance in noisy environments.
Single point-to-point net topologies are recommended with a
100 Ω termination resistor placed as close to the receiver as
possible. No far-end receiver termination and poor differential
trace routing may result in timing errors. It is recommended
that the trace length be no longer than 24 inches and that the
differential output traces be kept close together and at equal
lengths. An example of the FCO, DCO, and data stream with
proper trace length and position can be found in Figure 64.
By asserting the STBY pin high, the AD9273 is placed into a
standby mode. In this state, the device typically dissipates
140 mW. During standby, the entire part is powered down
except the internal references. The LVDS output drivers are
placed into a high impedance state. This mode is well suited for
applications that require power savings because it allows the
device to be powered down when not in use and then quickly
powered up. The time to power this device back up is also greatly
reduced. The AD9273 returns to normal operating mode when
the STBY pin is pulled low. This pin is both 1.8 V and 3.3 V
tolerant.
In power-down mode, low power dissipation is achieved by
shutting down the reference, reference buffer, PLL, and biasing
networks. The decoupling capacitors on VREF are discharged
when entering power-down mode and must be recharged when
returning to normal operation. As a result, the wake-up time is
related to the time spent in the power-down mode: shorter
cycles result in proportionally shorter wake-up times. To restore
the device to full operation, approximately 0.5 ms is required when
using the recommended 1 ꢁF and 0.1 ꢁF decoupling capacitors
on the VREF pin and a 0.01 ꢁF capacitor on the GAIN pins.
Most of this time is dependent on the gain decoupling: higher
value decoupling capacitors on the GAIN pins result in longer
wake-up times.
5.0ns/DIV
CH1 500mV/DIV Ω
CH2 500mV/DIV Ω
CH3 500mV/DIV Ω
Figure 64. LVDS Output Timing Example in ANSI-644 Mode (Default)
An example of the LVDS output using the ANSI-644 standard
(default) data eye and a time interval error (TIE) jitter histogram
with trace lengths of less than 24 inches on regular FR-4 material
is shown in Figure 65. Figure 66 shows an example of the trace
lengths exceeding 24 inches on regular FR-4 material. Notice
that the TIE jitter histogram reflects the decrease of the data eye
opening as the edge deviates from the ideal position; therefore,
the user must determine if the waveforms meet the timing budget
of the design when the trace lengths exceed 24 inches.
There are a number of other power-down options available
when using the SPI port interface. The user can individually
power down each channel or put the entire device into standby
mode. This allows the user to keep the internal PLL powered up
when fast wake-up times are required. The wake-up time is
slightly dependent on gain. To achieve a 1 ꢁs wake-up time
when the device is in standby mode, 0.8 V must be applied to
the GAIN pins. See Table 17 for more details on using these
features.
Additional SPI options allow the user to further increase the
internal termination and therefore increase the current of all
eight outputs in order to drive longer trace lengths (see Figure 67).
Even though this produces sharper rise and fall times on the
data edges, is less prone to bit errors, and improves frequency
distribution (see Figure 67), the power dissipation of the DRVDD
supply increases when this option is used.
Digital Outputs and Timing
The AD9273 differential outputs conform to the ANSI-644 LVDS
standard by default at power-up. This can be changed to a low
power, reduced-signal option similar to the IEEE 1596.3 standard
by using the SDIO pin or via the SPI. This LVDS standard can
further reduce the overall power dissipation of the device by
approximately 36 mW. See the SDIO Pin section or Table 17 for
more information.
In cases that require increased driver strength to the DCO and
FCO outputs because of load mismatch, Register 0x15 allows
the user to double the drive strength. To do this, set Bit 0 in
Register 0x15. Note that this feature cannot be used with Bit 4
and Bit 5 in Register 0x15 because these bits take precedence
over this feature. See Table 17 for more details.
The LVDS driver current is derived on chip and sets the output
current at each output equal to a nominal 3.5 mA. A 100 Ω differ-
ential termination resistor placed at the LVDS receiver inputs
results in a nominal 350 mV swing at the receiver.
Rev. B | Page 33 of 48
AD9273
600
400
300
EYE: ALL BITS
EYE: ALL BITS
ULS: 2398/2398
ULS: 2399/2399
400
200
200
100
100
0
0
–100
–200
–400
–600
–100
–200
–300
–400
–1.5ns
–1.0ns –0.5ns
0ns
0.5ns
1.0ns
1.5ns
–1.5ns
–1.0ns –0.5ns
0ns
0.5ns
1.0ns
1.5ns
25
20
25
20
15
10
5
15
10
5
0
0
–200ps
–100ps
0ps
100ps
200ps
–200ps
–100ps
0ps
100ps
200ps
Figure 65. Data Eye for LVDS Outputs in ANSI-644 Mode with Trace Lengths
of Less than 24 Inches on Standard FR-4
Figure 66. Data Eye for LVDS Outputs in ANSI-644 Mode with Trace Lengths
of Greater than 24 Inches on Standard FR-4
Rev. B | Page 34 of 48
AD9273
600
400
200
The format of the output data is offset binary by default. An
EYE: ALL BITS
ULS: 2396/2396
example of the output coding format can be found in Table 11.
To change the output data format to twos complement, see the
Memory Map section.
Table 11. Digital Output Coding
(VIN+) − (VIN−),
Code Input Span = 2 V p-p (V)
Digital Output Offset Binary
(D11 ... D0)
0
4095
2048
2047
0
+1.00
1111 1111 1111
1000 0000 0000
0111 1111 1111
0000 0000 0000
–200
0.00
−0.000488
−1.00
–400
–600
–1.5ns
–1.0ns –0.5ns
0ns
0.5ns
1.0ns
1.5ns
Data from each ADC is serialized and provided on a separate
channel. The data rate for each serial stream is equal to 12 bits
times the sample clock rate, with a maximum of 600 Mbps
(12 bits × 50 MSPS = 600 Mbps). The lowest typical conversion
rate is 10 MSPS, but the PLL can be set up for encode rates as
low as 5 MSPS via the SPI if lower sample rates are required for
a specific application. See Table 17 for details on enabling this
feature.
25
20
15
10
5
Two output clocks are provided to assist in capturing data from
the AD9273. DCO is used to clock the output data and is equal
to six times the sampling clock rate. Data is clocked out of the
AD9273 and must be captured on the rising and falling edges of
the DCO that supports double data rate (DDR) capturing. The
frame clock output (FCO ) is used to signal the start of a new
output byte and is equal to the sampling clock rate. See the
timing diagram shown in Figure 2 for more information.
0
–200ps
–100ps
0ps
100ps
200ps
Figure 67. Data Eye for LVDS Outputs in ANSI-644 Mode with 100 Ω Termination
Resistor and Trace Lengths of Greater than 24 Inches on Standard FR-4
Table 12. Flexible Output Test Modes
Output Test Mode
Bit Sequence
Subject to Data
Format Select
Pattern Name
Off (default)
Digital Output Word 1
N/A
Digital Output Word 2
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
N/A
N/A
Yes
Yes
Yes
No
Yes
Yes
No
No
No
No
No
No
Midscale short
+Full-scale short
−Full-scale short
Checkerboard output
PN sequence long
PN sequence short
One-/zero-word toggle
User input
1000 0000 0000
1111 1111 1111
0000 0000 0000
1010 1010 1010
N/A
1000 0000 0000
1111 1111 1111
0000 0000 0000
0101 0101 0101
N/A
N/A
0000 0000 0000
Register 0x1B and Register 0x1C
N/A
N/A
N/A
N/A
N/A
1111 1111 1111
Register 0x19 and Register 0x1A
1010 1010 1010
0000 0011 1111
1000 0000 0000
1010 0011 0011
1-/0-bit toggle
1× sync
One bit high
1100
Mixed bit frequency
Rev. B | Page 35 of 48
AD9273
When using the serial port interface (SPI), the DCO phase can
be adjusted in 60° increments relative to the data edge. This
enables the user to refine system timing margins if required.
The default DCO timing, as shown in Figure 2, is 90° relative
to the output data edge.
Consult the Memory Map section for information on how to change
these additional digital output timing features through the SPI.
SDIO Pin
This pin is required to operate the SPI. It has an internal 30 kΩ
pull-down resistor that pulls this pin low and is only 1.8 V
tolerant. If applications require that this pin be driven from a
3.3 V logic level, insert a 1 kΩ resistor in series with this pin to
limit the current.
An 8-, 10-, and 14-bit serial stream can also be initiated from the
SPI. This allows the user to implement different serial streams and
to test the device’s compatibility with lower and higher resolution
systems. When changing the resolution to an 8- or 10-bit serial
stream, the data stream is shortened. When using the 14-bit
option, the data stream stuffs two 0s at the end of the normal
14-bit serial data.
SCLK Pin
This pin is required to operate the SPI port interface. It has an
internal 30 kΩ pull-down resistor that pulls this pin low and is
both 1.8 V and 3.3 V tolerant.
When the SPI is used, all of the data outputs can also be inverted
from their nominal state. This is not to be confused with inverting
the serial stream to an LSB-first mode. In default mode, as shown
in Figure 2, the MSB is represented first in the data output serial
stream. However, this can be inverted so that the LSB is repre-
sented first in the data output serial stream (see Figure 3).
CSB Pin
This pin is required to operate the SPI port interface. It has an
internal 70 kΩ pull-up resistor that pulls this pin high and is both
1.8 V and 3.3 V tolerant.
RBIAS Pin
There are 12 digital output test pattern options available that
can be initiated through the SPI. This is a useful feature when
validating receiver capture and timing. Refer to Table 12 for the
output bit sequencing options available. Some test patterns have
two serial sequential words and can be alternated in various
ways, depending on the test pattern chosen. Note that some
patterns may not adhere to the data format select option. In
addition, customer user patterns can be assigned in the 0x19,
0x1A, 0x1B, and 0x1C register addresses. All test mode options
except PN sequence short and PN sequence long can support
8- to 14-bit word lengths in order to verify data capture to the
receiver.
To set the internal core bias current of the ADC, place a resistor
nominally equal to 10.0 kΩ to ground at the RBIAS pin. Using
other than the recommended 10.0 kΩ resistor for RBIAS degrades
the performance of the device. Therefore, it is imperative that at
least a 1% tolerance on this resistor be used to achieve consistent
performance.
Voltage Reference
A stable and accurate 0.5 V voltage reference is built into the
AD9273. This is gained up internally by a factor of 2, setting
VREF to 1.0 V, which results in a full-scale differential input
span of 2.0 V p-p for the ADC. VREF is set internally by
default, but the VREF pin can be driven externally with a 1.0 V
reference to achieve more accuracy. However, this device does
not support ADC full-scale ranges below 2.0 V p-p.
The PN sequence short pattern produces a pseudorandom
bit sequence that repeats itself every 29 − 1 bits, or 511 bits. A
description of the PN sequence and how it is generated can be
found in Section 5.1 of the ITU-T 0.150 (05/96) standard. The
only difference is that the starting value is a specific value instead
of all 1s (see Table 13 for the initial values).
When applying the decoupling capacitors to the VREF pin, use
ceramic low-ESR capacitors. These capacitors should be close to
the reference pin and on the same layer of the PCB as the
AD9273. The VREF pin should have both a 0.1 ꢁF capacitor
and a 1 ꢁF capacitor connected in parallel to the analog ground.
These capacitor values are recommended for the ADC to
properly settle and acquire the next valid sample.
The PN sequence long pattern produces a pseudorandom bit
sequence that repeats itself every 223 − 1 bits, or 8,388,607 bits.
A description of the PN sequence and how it is generated can
be found in Section 5.6 of the ITU-T 0.150 (05/96) standard.
The only differences are that the starting value is a specific value
instead of all 1s and the AD9273 inverts the bit stream with
relation to the ITU standard (see Table 13 for the initial values).
The reference settings can be selected using the SPI. The settings
allow two options: using the internal reference or using an external
reference. The internal reference option is the default setting and
has a resulting differential span of 2 V p-p.
Table 13. PN Sequence
Table 14. SPI-Selectable Reference Settings
Initial
Value
First Three Output Samples
(MSB First)
Sequence
Resulting Resulting Differential
SPI-Selected Mode
VREF (V)
Span (V p-p)
2 × external reference
2.0
PN Sequence Short 0x0DF
PN Sequence Long 0x29B80A 0x591, 0xFD7, 0x0A3
0xDF9, 0x353, 0x301
External Reference
Internal Reference (Default) 1.0
N/A
Rev. B | Page 36 of 48
AD9273
Power and Ground Recommendations
the AD9273 exposed paddle, Pin 0. The copper plane should
have several vias to achieve the lowest possible resistive thermal
path for heat dissipation to flow through the bottom of the PCB.
These vias should be filled or plugged with nonconductive epoxy.
When connecting power to the AD9273, it is recommended
that two separate 1.8 V supplies be used: one for analog (AVDD)
and one for digital (DRVDD). If only one 1.8 V supply is
available, it should be routed to the AVDD1 first and then
tapped off and isolated with a ferrite bead or a filter choke
preceded by decoupling capacitors for the DRVDD. The user
should employ several decoupling capacitors on all supplies to
cover both high and low frequencies. These should be located
close to the point of entry at the PC board level and close to the
parts with minimal trace lengths.
To maximize the coverage and adhesion between the device and
PCB, partition the continuous copper pad by overlaying a silk-
screen or solder mask to divide this into several uniform sections.
This ensures several tie points between the two during the reflow
process. Using one continuous plane with no partitions only
guarantees one tie point between the AD9273 and PCB. See
Figure 68 for a PCB layout example. For more detailed infor-
mation on packaging and for more PCB layout examples, see
the AN-772 Application Note.
A single PC board ground plane should be sufficient when
using the AD9273. With proper decoupling and smart parti-
tioning of the PC board’s analog, digital, and clock sections,
optimum performance can be achieved easily.
SILKSCREEN PARTITION
PIN 1 INDICATOR
Exposed Paddle Thermal Heat Slug Recommendations
It is required that the exposed paddle on the underside of the
device be connected to a quiet analog ground to achieve the
best electrical and thermal performance of the AD9273. An
exposed continuous copper plane on the PCB should mate to
Figure 68. Typical PCB Layout
Rev. B | Page 37 of 48
AD9273
SERIAL PORT INTERFACE (SPI)
The AD9273 serial port interface allows the user to configure
the signal chain for specific functions or operations through a
structured register space provided inside the chip. This offers
the user added flexibility and customization depending on the
application. Addresses are accessed via the serial port and can
be written to or read from via the port. Memory is organized
into bytes that can be further divided down into fields, as doc-
umented in the Memory Map section. Detailed operational
information can be found in the AN-877 Application Note,
Interfacing to High Speed ADCs via SPI.
In addition to the operation modes, the SPI port can be
configured to operate in different manners. For applications
that do not require a control port, the CSB line can be tied and
held high. This places the remainder of the SPI pins in their
secondary mode, as defined in the SDIO Pin and SCLK Pin
sections. CSB can also be tied low to enable 2-wire mode. When
CSB is tied low, SCLK and SDIO are the only pins required for
communication. Although the device is synchronized during
power-up, caution must be exercised when using this mode to
ensure that the serial port remains synchronized with the CSB
line. When operating in 2-wire mode, it is recommended to use
a 1-, 2-, or 3-byte transfer exclusively. Without an active CSB
line, streaming mode can be entered but not exited.
There are three pins that define the serial port interface (SPI):
the SCLK, SDIO, and CSB pins. The SCLK (serial clock) is used
to synchronize the read and write data presented to the device.
The SDIO (serial data input/output) is a dual-purpose pin that
allows data to be sent to and read from the device’s internal
memory map registers. The CSB (chip select bar) is an active
low control that enables or disables the read and write cycles
(see Table 15).
In addition to word length, the instruction phase determines if
the serial frame is a read or write operation, allowing the serial
port to be used to both program the chip and read the contents
of the on-chip memory. If the instruction is a readback operation,
performing a readback causes the serial data input/output (SDIO)
pin to change direction from an input to an output at the
appropriate point in the serial frame.
Table 15. Serial Port Pins
Pin
Function
Data can be sent in MSB- or LSB-first mode. MSB-first mode
is the default at power-up and can be changed by adjusting the
configuration register. For more information about this and
other features, see the AN-877 Application Note, Interfacing to
High Speed ADCs via SPI.
SCLK
Serial clock. The serial shift clock input. SCLK is used to
synchronize serial interface reads and writes.
Serial data input/output. A dual-purpose pin. The typical
role for this pin is as an input or output, depending on
the instruction sent and the relative position in the
timing frame.
SDIO
CSB
HARDWARE INTERFACE
Chip select bar (active low). This control gates the read
and write cycles.
The pins described in Table 15 constitute the physical interface
between the user’s programming device and the serial port of
the AD9273. The SCLK and CSB pins function as inputs when
using the SPI interface. The SDIO pin is bidirectional, functioning
as an input during write phases and as an output during readback.
The falling edge of the CSB in conjunction with the rising edge of
the SCLK determines the start of the framing sequence. During an
instruction phase, a 16-bit instruction is transmitted, followed by
one or more data bytes, which is determined by Bit Field W0 and
Bit Field W1. An example of the serial timing and its definitions
can be found in Figure 70 and Table 16.
In cases where multiple SDIO pins share a common connection,
care should be taken to ensure that proper VOH levels are met.
Figure 69 shows the number of SDIO pins that can be connected
together, assuming the same load as the AD9273, as well as the
resulting VOH level.
During normal operation, CSB is used to signal to the device
that SPI commands are to be received and processed. When
CSB is brought low, the device processes SCLK and SDIO to
process instructions. Normally, CSB remains low until the
communication cycle is complete. However, if connected to a
slow device, CSB can be brought high between bytes, allowing
older microcontrollers enough time to transfer data into shift
registers. CSB can be stalled when transferring one, two, or three
bytes of data. When W0 and W1 are set to 11, the device enters
streaming mode and continues to process data, either reading
or writing, until CSB is taken high to end the communication
cycle. This allows complete memory transfers without having
to provide additional instructtions. Regardless of the mode,
if CSB is taken high in the middle of any byte transfer, the SPI
state machine is reset and the device waits for a new instruction.
1.800
1.795
1.790
1.785
1.780
1.775
1.770
1.765
1.760
1.755
1.750
1.745
1.740
1.735
1.730
1.725
1.720
1.715
0
10
20
30
40
50
60
70
80
90
100
NUMBER OF SDIO PINS CONNECTED TOGETHER
Figure 69. SDIO Pin Loading
Rev. B | Page 38 of 48
AD9273
This interface is flexible enough to be controlled by either serial
PROMS or PIC mirocontrollers. This provides the user with
an alternative method, other than a full SPI controller, for
programming the device (see the AN-812 Application Note).
If the user chooses not to use the SPI interface, these pins serve
a dual function and are associated with secondary functions
when the CSB is strapped to AVDD during device power-up.
See the SDIO Pin and SCLK Pin sections for details on which
pin-strappable functions are supported on the SPI pins.
tDS
tHI
tCLK
tH
tS
tDH
tLO
CSB
SCLK DON’T CARE
SDIO DON’T CARE
DON’T CARE
R/W
W1
W0
A12
A11
A10
A9
A8
A7
D5
D4
D3
D2
D1
D0
DON’T CARE
Figure 70. Serial Timing Details
Table 16. Serial Timing Definitions
Parameter
Minimum Timing (ns)
Description
tDS
5
2
40
5
Setup time between the data and the rising edge of SCLK
Hold time between the data and the rising edge of SCLK
Period of the clock
tDH
tCLK
tS
Setup time between CSB and SCLK
tH
2
Hold time between CSB and SCLK
tHI
tLO
tEN_SDIO
16
16
10
Minimum period that SCLK should be in a logic high state
Minimum period that SCLK should be in a logic low state
Minimum time for the SDIO pin to switch from an input to an output relative to the SCLK
falling edge (not shown in Figure 70)
tDIS_SDIO
10
Minimum time for the SDIO pin to switch from an output to an input relative to the SCLK
rising edge (not shown in Figure 70)
Rev. B | Page 39 of 48
AD9273
MEMORY MAP
READING THE MEMORY MAP TABLE
RESERVED LOCATIONS
Undefined memory locations should not be written to except
when writing the default values suggested in this data sheet.
Addresses that have values marked as 0 should be considered
reserved and have a 0 written into their registers during power-up.
Each row in the memory map table has eight address locations.
The memory map is roughly divided into three sections: the
chip configuration register map (Address 0x00 to Address 0x02),
the device index and transfer register map (Address 0x04 to
Address 0xFF), and the ADC functions register map
(Address 0x08 to Address 0x2D).
DEFAULT VALUES
After a reset, critical registers are automatically loaded with
default values. These values are indicated in Table 17, where an
X refers to an undefined feature.
The leftmost column of the memory map indicates the register
address number, and the default value is shown in the second
rightmost column. The Bit 7 (MSB) column is the start of the
default hexadecimal value given. For example, Address 0x09,
the clock register, has a default value of 0x01, meaning that Bit 7
= 0, Bit 6 = 0, Bit 5 = 0, Bit 4 = 0, Bit 3 = 0, Bit 2 = 0, Bit 1 = 0,
and Bit 0 = 1, or 0000 0001 in binary. This setting is the default
for the duty cycle stabilizer in the on condition. By writing a 0
to Bit 0 of this address followed by an 0x01 to the SW transfer
bit in Register 0xFF, the duty cycle stabilizer turns off. It is
important to follow each writing sequence with a write to the
SW transfer bit to update the SPI registers.
LOGIC LEVELS
An explanation of various registers follows: “bit is set” is
synonymous with “bit is set to Logic 1” or “writing Logic 1 for
the bit.” Similarly, “clear a bit” is synonymous with “bit is set to
Logic 0” or “writing Logic 0 for the bit.”
Caution
All registers except Register 0x00, Register 0x02, Register 0x04,
Register 0x05, and Register 0xFF are buffered with a master
slave latch and require writing to the transfer bit. For more
information on this and other functions, consult the AN-877
Application Note, Interfacing to High Speed ADCs via SPI.
Rev. B | Page 40 of 48
AD9273
Table 17. AD9273 Memory Map Register
Addr.
Bit 7
Bit 0
Default Default Notes/
(Hex) Register Name
(MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
(LSB)
Value
Comments
Chip Configuration Registers
00
CHIP_PORT_CONFIG
0
LSB first
1 = on
Soft
reset
1
1
Soft
reset
LSB first
1 = on
0
0x18
The nibbles
should be
0 = off
(default)
1 = on
0 = off
(default)
1 = on
0 = off
(default)
0 = off
(default)
mirrored so that
LSB- or MSB-first
mode is set cor-
rectly regardless
of shift mode.
01
02
CHIP_ID
Chip ID Bits[7:0]
(AD9273 = 0x2F, default)
Read
only
Default is unique
chip ID, different
for each device.
This is a read-only
register.
CHIP_GRADE
X
X
Child ID[5:4]
X
X
X
X
0x00
Child ID used to
differentiate
graded devices.
(identify device
variants of Chip ID)
00 = 40 MSPS
(default)
01 = 25 MSPS
10 = 50 MSPS
Device Index and Transfer Registers
04
05
FF
DEVICE_INDEX_2
DEVICE_INDEX_1
DEVICE_UPDATE
X
X
X
X
X
X
X
X
Data
Data
Data
Data
0x0F
0x0F
0x00
Bits are set to
Channel Channel Channel Channel
H
1 = on
(default)
0 = off
determine which
on-chip device
receives the next
write command.
G
F
E
1 = on
(default)
0 = off
1 = on
(default)
0 = off
1 = on
(default)
0 = off
Clock
Clock
Data
Data
Data
Data
Bits are set to
Channel Channel Channel Channel Channel Channel
DCO
1 = on
0 = off
(default)
determine which
on-chip device
receives the next
write command.
FCO
1 = on
0 = off
D
C
B
A
1 = on
(default)
1 = on
(default)
0 = off
1 = on
(default)
0 = off
1 = on
(default)
0 = off
(default) 0 = off
X
X
X
X
X
SW
Synchronously
transfers data
from the master
shift register to
the slave.
transfer
1 = on
0 = off
(default)
ADC Functions Registers
08
09
0D
Modes
X
X
X
X
X
X
X
X
0
Internal power-down mode
000 = chip run (default)
001 = full power-down
010 = standby
011 = reset
100 = CW mode (TGC PDWN)
0x00
0x01
0x00
Determines
various generic
modes of chip
operation
(global).
Clock
X
X
X
Duty
cycle
Turns the internal
duty cycle stabilizer
on and off
stabilizer
1 = on
(default)
0 = off
(global).
TEST_IO
User test mode
00 = off (default)
01 = on, single
alternate
Reset PN Reset PN Output test mode—see Table 12
long
gen
1 = on
0 = off
When this register
is set, the test data
is placed on the
output pins in
place of normal
data. (Local, expect
for PN sequence.)
short
gen
1 = on
0 = off
0000 = off (default)
0001 = midscale short
0010 = +FS short
10 = on, single once
11 = on, alternate once (default) (default) 0100 = checkerboard output
0101 = PN sequence long
0011 = −FS short
0110 = PN sequence short
0111 = one-/zero-word toggle
1000 = user input
1001 = 1-/0-bit toggle
1010 = 1× sync
1011 = one bit high
1100 = mixed bit frequency (format
determined by the OUTPUT_MODE register)
Rev. B | Page 41 of 48
AD9273
Addr.
Bit 7
Bit 0
Default Default Notes/
(Hex) Register Name
(MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
(LSB)
Value
Comments
0F
FLEX_CHANNEL_
INPUT
Filter cutoff frequency control
0000 = 1.3 × 1/3 × fSAMPLE
0001 = 1.2 × 1/3 × fSAMPLE
0010 = 1.1 × 1/3 × fSAMPLE
0011 = 1.0 × 1/3 × fSAMPLE (default)
0100 = 0.9 × 1/3 × fSAMPLE
0101 = 0.8 × 1/3 × fSAMPLE
0110 = 0.7 × 1/3 × fSAMPLE
1000 = 1.3 × 1/4.5 × fSAMPLE
1001 = 1.2 × 1/4.5 × fSAMPLE
1010 = 1.1 × 1/4.5 × fSAMPLE
1011 = 1.0 × 1/4.5 × fSAMPLE
1100 = 0.9 × 1/4.5 × fSAMPLE
1101 = 0.8 × 1/4.5 × fSAMPLE
1110 = 0.7 × 1/4.5 × fSAMPLE
X
X
X
X
0x30
Antialiasing filter
cutoff (global).
10
11
FLEX_OFFSET
FLEX_GAIN
X
X
6-bit LNA offset adjustment
10 0000 = LNA bias high, mid-high, mid-low (default)
10 0001 = LNA bias low
0x20
0x06
LNA force offset
correction
(local).
X
X
X
X
PGA gain
LNA gain
LNA and PGA
gain adjustment
(global).
00 = 21 dB
01 = 24 dB (default)
10 = 27 dB
00 = 15.6 dB
01 = 17.9 dB
10 = 21.3 dB
(default)
11 = 30 dB
12
14
BIAS_CURRENT
OUTPUT_MODE
X
X
X
X
X
1
X
LNA bias
00 = high
01 = mid-high
(default)
10 = mid-low
11 = low
0x08
0x00
LNA bias current
adjustment
(global).
0 = LVDS
ANSI-644
(default)
1 = LVDS
low power,
(IEEE
X
X
X
Output
invert
1 = on
0 = off
(default)
00 = offset binary
(default)
01 = twos
Configures the
outputs and the
format of the data
(Bits[7:3] and
Bits[1:0] are global;
Bit 2 is local).
complement
1596.3
similar)
15
OUTPUT_ADJUST
X
X
Output driver
termination
00 = none (default)
01 = 200 Ω
10 = 100 Ω
11 = 100 Ω
X
X
X
DCO
and
FCO
2× drive
strength
1 = on
0 = off
(default)
0x00
Determines LVDS
or other output
properties. Pri-
marily functions to
set the LVDS span
and common-
mode levels in
place of an
external resistor
(Bits[7:1] are global;
Bit 0 is local).
16
OUTPUT_PHASE
X
X
X
X
0011 = output clock phase adjust
(0000 through 1010)
0x03
On devices that
utilize global
0000 = 0° relative to data edge
0001 = 60° relative to data edge
0010 = 120° relative to data edge
clock divide,
determines which
phase of the
divider output is
used to supply
the output clock.
Internal latching
is unaffected.
0011 = 180° relative to data edge (default)
0100 = 240° relative to data edge
0101 = 300° relative to data edge
0110 = 360° relative to data edge
0111 = 420° relative to data edge
1000 = 480° relative to data edge
1001 = 540° relative to data edge
1010 = 600° relative to data edge
1011 to 1111 = 660° relative to data edge
18
FLEX_VREF
X
0 =
X
X
X
X
X
X
0x00
Select internal
reference
(recommended
default) or external
reference (global).
internal
reference
1 =
external
reference
Rev. B | Page 42 of 48
AD9273
Addr.
Bit 7
Bit 0
Default Default Notes/
(Hex) Register Name
(MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
(LSB)
Value
Comments
19
1A
1B
1C
21
USER_PATT1_LSB
USER_PATT1_MSB
USER_PATT2_LSB
USER_PATT2_MSB
SERIAL_CONTROL
B7
B6
B5
B4
B3
B2
B1
B0
B8
B0
B8
0x00
User-defined
pattern, 1 LSB
(global).
B15
B7
B14
B6
B13
B5
B12
B4
B11
B3
B10
B2
B9
B1
B9
0x00
0x00
0x00
0x00
User-defined
pattern, 1 MSB
(global).
User-defined
pattern, 2 LSB
(global).
B15
B14
X
B13
X
B12
X
B11
B10
User-defined
pattern, 2 MSB
(global).
LSB first
1 = on
0 = off
<10
MSPS,
low
encode
rate
000 = 12 bits (default, normal
bit stream)
001 = 8 bits
010 = 10 bits
011 = 12 bits
Serial stream
control. Default
causes MSB first
and the native bit
stream (global).
(default)
mode
1 = on
0 = off
(default)
100 = 14 bits
22
2B
SERIAL_CH_STAT
FLEX_FILTER
X
X
X
X
X
X
X
X
X
Channel Channel 0x00
Used to power
down individual
sections of a
output
reset
power-
down
1 = on
0 = off
1 = on
0 = off
converter (local).
(default) (default)
Enable
High-pass filter cutoff
0000 = fLP/20.7
0001 = fLP /11.5
0010 = fLP /7.9
0011 = fLP /6.0
0100 = fLP /4.9
0101 = fLP /4.1
0110 = fLP /3.5
0111 = fLP /3.1
0x00
Filter cutoff
(global). (fLP =
low-pass filter
cutoff frequency.)
automatic
low-pass
tuning
1 = on
(self-
clearing)
2C
2D
ANALOG_INPUT
X
X
X
X
X
X
X
X
LOSW-x connect
00 = high-Z
01 = (−)LNA output
10 = (+)LNA output
11 = high-Z
0x00
0x00
LNA active
termination/input
impedance
(global).
CROSS_POINT_
SWITCH
Crosspoint switch enable
Crosspoint switch
enable (local).
10 0000 = CWD0 (differential)
10 0001 = CWD1 (differential)
10 0010 = CWD2 (differential)
10 0011 = CWD3 (differential)
10 0100 = CWD4 (differential)
10 0101 = CWD5 (differential)
10 0110 = CWD6 (differential)
10 0111 = CWD7 (differential)
11 0000 = CWD0+ (single ended)
11 0001 = CWD1+ (single ended)
11 0010 = CWD2+ (single ended)
11 0011 = CWD3+ (single ended)
11 0100 = CWD4+ (single ended)
11 0101 = CWD5+ (single ended)
11 0110 = CWD6+ (single ended)
11 0111 = CWD7+ (single ended)
11 1000 = CWD0− (single ended)
11 1001 = CWD1− (single ended)
11 1010 = CWD2− (single ended)
11 1011 = CWD3− (single ended)
11 1100 = CWD4− (single ended)
11 1101 = CWD5− (single ended)
11 1110 = CWD6− (single ended)
11 1111 = CWD7− (single ended)
0x xxxx = power down CW channel (default)
Rev. B | Page 43 of 48
AD9273
OUTLINE DIMENSIONS
16.00 BSC SQ
1.20
MAX
0.75
0.60
0.45
14.00 BSC SQ
76
75
100
76
75
100
1
1
PIN 1
EXPOSED
PAD
9.50 SQ
TOP VIEW
(PINS DOWN)
0° MIN
1.05
1.00
0.95
0.20
0.09
7°
BOTTOM VIEW
(PINS UP)
51
51
25
25
26
50
50
26
3.5°
0°
0.50 BSC
LEAD PITCH
0.27
0.22
0.17
VIEW A
0.15
0.05
SEATING
PLANE
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
0.08 MAX
COPLANARITY
SECTION OF THIS DATA SHEET.
VIEW A
ROTATED 90° CCW
COMPLIANT TO JEDEC STANDARDS MS-026-AED-HD
Figure 71. 100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
(SV-100-3)
Dimensions shown in millimeters
A1 CORNER
INDEX AREA
10.10
10.00
9.90
9
7
3
1
11
5
12
10
8
6
4
2
A
B
C
D
E
F
G
H
J
BALL A1
INDICATOR
8.80
BSC SQ
TOP VIEW
K
L
M
BOTTOM VIEW
DETAIL A
0.80 BSC
DETAIL A
1.40 MAX
1.00
0.85
0.43 MAX
0.25 MIN
COPLANARITY
0.12 MAX
0.55
0.50
0.45
SEATING
PLANE
BALL DIAMETER
COMPLIANT WITH JEDEC STANDARDS MO-205-AC.
Figure 72. 144-Ball Chip Scale Package, Ball Grid Array [CSP_BGA]
(BC-144-1)
Dimensions shown in millimeters
Rev. B | Page 44 of 48
AD9273
ORDERING GUIDE
Temperature
Range
Package
Option
Model
Package Description
AD9273BSVZ-501
AD9273BSVZRL-501
AD9273BSVZ-401
AD9273BSVZRL-401
AD9273BSVZ-251
AD9273BSVZRL-251
AD9273BBCZ-251
AD9273BBCZ-401
AD9273BBCZ-501
AD9273-50EBZ1
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP] Tape and Reel
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP] Tape and Reel
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP] Tape and Reel
144-Ball Chip Scale Package, Ball Grid Array [CSP_BGA]
144-Ball Chip Scale Package, Ball Grid Array [CSP_BGA]
144-Ball Chip Scale Package, Ball Grid Array [CSP_BGA]
Evaluation Board, 100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
SV-100-3
SV-100-3
SV-100-3
SV-100-3
SV-100-3
SV-100-3
BC-144-1
BC-144-1
BC-144-1
1 Z = RoHS Compliant Part.
Rev. B | Page 45 of 48
AD9273
NOTES
Rev. B | Page 46 of 48
AD9273
NOTES
Rev. B | Page 47 of 48
AD9273
NOTES
©2009 Analog Devices, Inc. All rights reserved. Trademarks and
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D07030-0-7/09(B)
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