2-Channel, Software-Selectable, True
Bipolar Input, 1 MSPS, 12-Bit Plus Sign ADC
AD7322
FEATURES
12-bit plus sign SAR ADC
True bipolar input ranges
Software-selectable input ranges
±10 V, ±5 V, ±2.5 V, 0 V to +10 V
1 MSPS throughput rate
Two analog input channels with channel sequencer
Single-ended, true differential, and pseudo differential
analog input capability
High analog input impedance
Low power: 21 mW
Full power signal bandwidth: 22 MHz
Internal 2.5 V reference
High speed serial interface
Power-down modes
14-lead TSSOP package
iCMOS
process technology
FUNCTIONAL BLOCK DIAGRAM
V
DD
REFIN/OUT
V
CC
AD7322
2.5V
VREF
I/P
MUX
T/H
V
IN
0
V
IN
1
13-BIT
SUCCESSIVE
APPROXIMATION
ADC
DOUT
CHANNEL
SEQUENCER
CONTROL LOGIC
AND REGISTERS
SCLK
CS
DIN
V
DRIVE
AGND
V
SS
DGND
04863-001
Figure 1.
GENERAL DESCRIPTION
The AD7322
1
is a 2-channel, 12-bit plus sign, successive approx-
imation analog-to-digital converter (ADC) designed on the
iCMOS™
(industrial CMOS) process.
iCMOS
is a process
combining high voltage silicon with submicron CMOS and
complementary bipolar technologies. It enables the develop-
ment of a wide range of high performance analog ICs capable of
33 V operation in a footprint that no previous generation of high
voltage parts could achieve. Unlike analog ICs using conventional
CMOS processes,
iCMOS
components can accept bipolar input
signals while providing increased performance, dramatically
reduced power consumption, and reduced package size.
The AD7322 can accept true bipolar analog input signals. The
AD7322 has four software-selectable input ranges, ±10 V, ±5 V,
±2.5 V, and 0 V to +10 V. Each analog input channel can be
independently programmed to one of the four input ranges.
The analog input channels on the AD7322 can be programmed
to be single-ended, true differential, or pseudo differential.
The ADC contains a 2.5 V internal reference. The AD7322 also
allows for external reference operation. If a 3 V reference is
applied to the REFIN/OUT pin, the AD7322 can accept a true
bipolar ±12 V analog input. Minimum ±12 V V
DD
and V
SS
supplies are required for the ±12 V input range. The ADC has a
high speed serial interface that can operate at throughput rates
up to 1 MSPS.
1
PRODUCT HIGHLIGHTS
1.
2.
The AD7322 can accept true bipolar analog input signals,
±10 V, ±5 V, and ±2.5 V, and 0 V to +10 V unipolar signals.
The two analog inputs can be configured as two single-
ended inputs, one true differential input, or one pseudo
differential input.
1 MSPS serial interface. SPI-/QSPI™-/DSP-/MICROWIRE™-
compatible interface.
Low power, 31 mW maximum, at 1 MSPS throughput rate.
Channel sequencer.
3.
4.
5.
Table 1. Similar Devices
Device
Number
AD7329
AD7328
AD7327
AD7324
AD7323
AD7321
Throughput
Rate
1000 kSPS
1000 kSPS
500 kSPS
1000 kSPS
500 kSPS
500 kSPS
Number of bits
12-bit plus sign
12-bit plus sign
12-bit plus sign
12-bit plus sign
12-bit plus sign
12-bit plus sign
Number of
Channels
8
8
8
4
4
2
Protected by U.S. Patent No. 6,731,232.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2005–2010 Analog Devices, Inc. All rights reserved.
AD7322
TABLE OF CONTENTS
Features .............................................................................................. 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Timing Specifications .................................................................. 6
Absolute Maximum Ratings............................................................ 7
ESD Caution .................................................................................. 7
Pin Configuration and Function Descriptions ............................. 8
Typical Performance Characteristics ............................................. 9
Terminology .................................................................................... 13
Theory of Operation ...................................................................... 15
Circuit Information .................................................................... 15
Converter Operation .................................................................. 15
Analog Input Structure .............................................................. 16
Typical Connection Diagram ................................................... 18
Analog Input ............................................................................... 18
Driver Amplifier Choice ............................................................ 20
Registers ........................................................................................... 21
Addressing Registers .................................................................. 21
Control Register ......................................................................... 22
Range Register ............................................................................ 24
Sequencer Operation ..................................................................... 25
Reference ..................................................................................... 26
V
DRIVE
............................................................................................ 26
Modes of Operation ....................................................................... 27
Normal Mode (PM1 = PM0 = 0) ............................................. 27
Full Shutdown Mode (PM1 = PM0 = 1) ................................. 27
Autoshutdown Mode (PM1 = 1, PM0 = 0) ............................. 28
Autostandby Mode (PM1 = 0, PM0 = 1) ................................ 28
Power vs. Throughput Rate ....................................................... 29
Serial Interface ................................................................................ 30
Microprocessor Interfacing ........................................................... 31
AD7322 to ADSP-21xx .............................................................. 31
AD7322 to ADSP-BF53x ........................................................... 31
Application Hints ........................................................................... 32
Layout and Grounding .............................................................. 32
Power Supply Configuration .................................................... 32
Outline Dimensions ....................................................................... 33
Ordering Guide .......................................................................... 33
REVISION HISTORY
1/10—Rev. 0 to Rev. A
Changes to Power Requirements, Normal Mode (Operational),
I
CC
and I
DRIVE
Parameter; and Power Dissipation, Normal Mode
Parameter, Table 2............................................................................. 5
Changes to Endnote 1, Table 4 ........................................................ 7
Changes to Table 6 .......................................................................... 15
Changes to Figure 25 and Figure 26 ............................................. 16
Changes to Figure 30 and Figure 31 ............................................. 17
Changes to Figure 33 and Figure 34 ............................................. 18
Changes to Figure 39 ...................................................................... 19
Changes to Figure 40 and Figure 41............................................. 20
Changes to Autostandby Mode (PM1 = 0, PM = 1) Section .... 28
Changes to Table 14 and Table 15 ................................................ 31
Added Power Supply Configuration Section .............................. 32
Added Table 16; Renumbered Sequentially ................................ 32
Added Figure 53; Renumbered Sequentially .............................. 32
Updated Outline Dimensions ....................................................... 33
12/05—Revision 0: Initial Version
Rev. A | Page 2 of
36
AD7322
SPECIFICATIONS
Unless otherwise noted, V
DD
= 12 V to 16.5 V, V
SS
= −12 V to −16.5 V, V
CC
= 4.75 V to 5.25 V, V
DRIVE
= 2.7 V to 5.25 V, V
REF
= 2.5 V to 3.0 V
internal/external, f
SCLK
= 20 MHz, f
S
= 1 MSPS, T
A
= T
MAX
to T
MIN
; for V
CC
< 4.75 V, all specifications are typical.
Table 2.
Parameter
DYNAMIC PERFORMANCE
Signal-to-Noise Ratio (SNR)
2
Signal-to-Noise + Distortion (SINAD)
2
1
Min
76
72.5
75
B Version
Typ
Max
Unit
dB
dB
dB
dB
dB
dB
76
72
72.5
Total Harmonic Distortion (THD)
2
−82
−77
−80
Peak Harmonic or Spurious Noise
(SFDR)
2
−82
−78
−79
Intermodulation Distortion (IMD)
2
Second-Order Terms
Third-Order Terms
Aperture Delay
3
Aperture Jitter
3
Common-Mode Rejection Ratio
(CMRR)
2
Channel-to-Channel Isolation
2
Full Power Bandwidth
DC ACCURACY
−80
−80
dB
dB
dB
dB
dB
dB
dB
dB
Test Conditions/Comments
f
IN
= 50 kHz sine wave
Differential mode
Single-ended/pseudo differential mode
Differential mode; ±2.5 V and ±5 V ranges
Differential mode; 0 V to +10 V and ±10 V ranges
Single-ended/pseudo differential mode;
±2.5 V and ±5 V ranges
Single-ended/pseudo differential mode;
0 V to +10 V and ±10 V ranges
Differential mode; ±2.5 V and ±5 V ranges
Differential mode; 0 V to +10 V and ±10 V ranges
Single-ended/pseudo differential mode;
±2.5 V and ±5 V ranges
Single-ended/pseudo differential mode;
0 V to +10 V and ±10 V ranges
Differential mode; ±2.5 V and ±5 V ranges
Differential mode; 0 V to +10 V and ±10 V ranges
Single-ended/pseudo differential mode;
±2.5 V and ±5 V ranges
Single-ended/pseudo differential mode;
0 V to +10 V and ±10 V ranges
fa = 50 kHz, fb = 30 kHz
−88
−90
7
50
−79
−72
22
5
dB
dB
ns
ps
dB
dB
MHz
MHz
Up to 100 kHz ripple frequency; see Figure 17
f
IN
on unselected channels up to 100 kHz; see Figure 14
At 3 dB
At 0.1 dB
All dc accuracy specifications are typical for 0 V to
10 V mode
Single-ended/pseudo differential mode:
1 LSB = FSR/4096; unless otherwise noted
Differential mode: 1 LSB = FSR/8192; unless
otherwise noted
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Single-ended/pseudo differential mode
(LSB = FSR/8192)
Resolution
No Missing Codes
13
12-bit plus
sign (13 bits)
11-bit plus
sign (12 bits)
±1.1
±1
−0.7/+1.2
Bits
Bits
Bits
LSB
LSB
LSB
Integral Nonlinearity
2
Rev. A | Page 3 of 36
AD7322
Parameter
Differential Nonlinearity
2
1
Min
B Version
Typ
Max
−0.9/+1.5
±0.9
Unit
LSB
LSB
LSB
−0.7/+1
Offset Error
2, 4
Offset Error Match
2, 4
Gain Error
2, 4
Gain Error Match
2, 4
Positive Full-Scale Error
2, 5
Positive Full-Scale Error Match
2, 5
Bipolar Zero Error
2, 5
Bipolar Zero Error Match
2, 5
Negative Full-Scale Error
2, 5
Negative Full-Scale Error Match
2, 5
ANALOG INPUT
Input Voltage Ranges
(Programmed via Range Register)
−4/+9
−7/+10
±0.6
±0.5
±8
±14
±0.5
±0.5
±4
±7
±0.5
±0.5
±8.5
±7.5
±0.5
±0.5
±4
±6
±0.5
±0.5
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
Test Conditions/Comments
Differential mode; guaranteed no missing codes to
13 bits
Single-ended mode; guaranteed no missing codes
to 12 bits
Single-ended/pseudo differential mode
(LSB = FSR/8192)
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Differential mode
Reference = 2.5 V; see Table 6
V
DD
= 10 V min, V
SS
= −10 V min, V
CC
= 2.7 V to 5.25 V
V
DD
= 5 V min, V
SS
= −5 V min, V
CC
= 2.7 V to 5.25 V
V
DD
= 5 V min, V
SS
= − 5 V min, V
CC
= 2.7 V to 5.25 V
V
DD
= 10 V min, V
SS
= AGND min, V
CC
= 2.7 V to 5.25 V
V
DD
= 16.5 V, V
SS
= −16.5 V, V
CC
= 5 V; see Figure 40
and Figure 41
Reference = 2.5 V; range = ±10 V
Reference = 2.5 V; range = ±5 V
Reference = 2.5 V; range = ±2.5 V
Reference = 2.5 V; range = 0 V to +10 V
V
IN
= V
DD
or V
SS
Per channel, V
IN
= V
DD
or V
SS
When in track, ±10 V range
When in track, ±5 V and 0 V to +10 V range
When in track, ±2.5 V range
When in hold, all ranges
±10
±5
±2.5
0 to 10
V
V
V
V
Pseudo Differential V
IN
(−) Input
Range
±3.5
±6
±5
+3/−5
DC Leakage Current
Input Capacitance
3
±80
3
13.5
16.5
21.5
3
2.5
10
2.5
±5
±10
3
7
25
3
±1
V
V
V
V
nA
nA
pF
pF
pF
pF
V
μA
pF
V
mV
mV
ppm/°C
Ω
REFERENCE INPUT/OUTPUT
Input Voltage Range
Input DC Leakage Current
Input Capacitance
Reference Output Voltage
Reference Output Voltage Error at
25°C
Reference Output Voltage
T
MIN
to T
MAX
Reference Temperature Coefficient
Reference Output Impedance
Rev. A | Page 4 of
36
AD7322
Parameter
LOGIC INPUTS
Input High Voltage, V
INH
Input Low Voltage, V
INL
Input Current, I
IN
Input Capacitance, C
IN3
LOGIC OUTPUTS
Output High Voltage, V
OH
Output Low Voltage, V
OL
Floating-State Leakage Current
Floating-State Output Capacitance
3
Output Coding
CONVERSION RATE
Conversion Time
Track-and-Hold Acquisition Time
2, 3
Throughput Rate
POWER REQUIREMENTS
V
DD
V
SS
V
CC
V
DRIVE
Normal Mode (Static)
Normal Mode (Operational)
I
DD
I
SS
I
CC
and I
DRIVE
Autostandby Mode (Dynamic)
I
DD
I
SS
I
CC
and I
DRIVE
Autoshutdown Mode (Static)
I
DD
I
SS
I
CC
and I
DRIVE
Full Shutdown Mode
I
DD
I
SS
I
CC
and I
DRIVE
POWER DISSIPATION
Normal Mode
Full Shutdown Mode
1
2
1
Min
2.4
B Version
Typ
Max
Unit
V
V
V
μA
pF
V
V
μA
pF
Test Conditions/Comments
0.8
0.4
±1
10
V
DRIVE
− 0.2
0.4
±1
5
Straight natural binary
Twos complement
800
305
1
770
12
−12
2.7
2.7
0.9
360
410
3.4
200
210
1.3
1
1
1
1
1
1
31
21
38.25
16.5
−16.5
5.25
5.25
V
CC
= 4.75 V to 5.25 V
V
CC
= 2.7 V to 3.6 V
V
IN
= 0 V or V
DRIVE
I
SOURCE
= 200 μA
I
SINK
= 200 μA
Coding bit set to 1 in control register
Coding bit set to 0 in control register
ns
ns
MSPS
kSPS
V
V
V
V
mA
μA
μA
mA
μA
μA
mA
μA
μA
μA
μA
μA
μA
mW
mW
μW
16 SCLK cycles with SCLK = 20 MHz
Full-scale step input; see the Terminology section
See the Serial Interface section; V
CC
= 4.75 V to 5.25 V
V
CC
< 4.75 V
Digital inputs = 0 V or V
DRIVE
See Table 6
See Table 6
See Table 6; typical specifications for V
CC
< 4.75 V
V
DD
/V
SS
= ±16.5 V, V
CC
/V
DRIVE
= 5.25 V
f
S
= 1 MSPS
V
DD
= 16.5 V
V
SS
= −16.5 V
V
CC
/V
DRIVE
= 5.25 V
f
S
= 250 kSPS
V
DD
= 16.5 V
V
SS
= −16.5 V
V
CC
/V
DRIVE
= 5.25 V
SCLK on or off
V
DD
= 16.5 V
V
SS
= −16.5 V
V
CC
/V
DRIVE
= 5.25 V
SCLK on or off
V
DD
= 16.5 V
V
SS
= −16.5 V
V
CC
/V
DRIVE
= 5.25 V
V
DD
= 16.5 V, V
SS
= −16.5 V, V
CC
= 5.25 V
V
DD
= 12 V, V
SS
= −12 V, V
CC
= 5 V
V
DD
= 16.5 V, V
SS
= −16.5 V, V
CC
= 5.25 V
Temperature range is −40°C to +85°C.
See the Terminology section.
3
Sample tested during initial release to ensure compliance.
4
Unipolar 0 V to 10 V range with straight binary output coding.
5
Bipolar range with twos complement output coding.
Rev. A | Page 5 of
36
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