Data Sheet
FEATURES
8-Channel, Software-Selectable,
True Bipolar Input, 12-Bit Plus Sign ADC
AD7328
FUNCTIONAL BLOCK DIAGRAM
V
DD
REFIN/OUT
V
CC
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
8 analog input channels with channel sequencer
Single-ended, true differential, and pseudo differential
analog input capability
High analog input impedance
Low power: 21 mW
Temperature indicator
Full power signal bandwidth: 22 MHz
Internal 2.5 V reference
High speed serial interface
Power-down modes
20-lead TSSOP package
iCMOS
process technology
AD7328
V
IN
0
V
IN
1
V
IN
2
V
IN
3
V
IN
4
V
IN
5
V
IN
6
V
IN
7
I/P
MUX
2.5V
VREF
T/H
13-BIT
SUCCESSIVE
APPROXIMATION
ADC
TEMPERATURE
INDICATOR
DOUT
CONTROL LOGIC
AND REGISTERS
CHANNEL
SEQUENCER
SCLK
CS
DIN
AGND
V
SS
DGND
Figure 1.
GENERAL DESCRIPTION
The
AD7328
1
is an 8-channel, 12-bit plus sign successive
approximation 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 development 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
AD7328
can accept true bipolar analog input signals. The
AD7328
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
AD7328
can be programmed to be
single-ended, true differential, or pseudo differential.
The ADC contains a 2.5 V internal reference. The
AD7328
also
allows for external reference operation. If a 3 V reference is applied
to the REFIN/OUT pin, the
AD7328
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.
PRODUCT HIGHLIGHTS
1.
2.
The
AD7328
can accept true bipolar analog input signals,
±10 V, ±5 V, ±2.5 V, and 0 V to +10 V unipolar signals.
The eight analog inputs can be configured as eight single-
ended inputs, four true differential input pairs, four pseudo
differential inputs, or seven pseudo differential inputs.
1 MSPS serial interface. SPI®-/QSPI™-/DSP-/MICROWIRE™-
compatible interface.
Low power, 31 mW, at a maximum throughput rate of
1 MSPS.
Channel sequencer.
Throughput
Rate
1000 kSPS
500 kSPS
1000 kSPS
500 kSPS
1000 kSPS
500 kSPS
Number of
Channels
8
8
4
4
2
2
3.
4.
5.
Table 1. Similar Product Selection
Device
Number
AD7329
AD7327
AD7324
AD7323
AD7322
AD7321
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
1
Protected by U.S. Patent No. 6,731,232.
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
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V
DRIVE
AD7328
TABLE OF CONTENTS
Features .............................................................................................. 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 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
Data Sheet
Sequence Register ....................................................................... 24
Range Registers ........................................................................... 24
Sequencer Operation ..................................................................... 25
Reference ..................................................................................... 27
V
DRIVE
............................................................................................ 27
Temperature Indicator ............................................................... 27
Modes of Operation ....................................................................... 28
Normal Mode (PM1 = PM0 = 0) ............................................. 28
Full Shutdown Mode (PM1 = PM0 = 1) ................................. 28
Autoshutdown Mode (PM1 = 1, PM0 = 0) ............................. 29
Autostandby Mode (PM1 = 0, PM0 = 1) ................................ 29
Power vs. Throughput Rate ....................................................... 30
Serial Interface ................................................................................ 31
Microprocessor Interfacing ........................................................... 32
AD7328 to ADSP-21xx .............................................................. 32
AD7328 to ADSP-BF53x ........................................................... 32
Applications Information .............................................................. 33
Layout and Grounding .............................................................. 33
Power Supply Configuration .................................................... 33
Outline Dimensions ....................................................................... 34
Ordering Guide .......................................................................... 34
REVISION HISTORY
1/14—Rev. B to Rev. C
Changes to Circuit Information Section and Table 6 ................ 15
Changes to Addressing Registers Section.................................... 21
Changes to Power Supply Configuration Section ...................... 33
Changes to Ordering Guide .......................................................... 34
2/10—Rev. A to Rev. B
Change to Product Highlights Section .......................................... 1
Changes to DC Accuracy Parameter, Test Conditions/
Comments, Table 2 ....................................................................... 3
Changes to Normal Mode (Operational) I
CC
and I
DRIVE
Parameter and to Power Dissipation Normal Mode
Parameter, Table 2 ........................................................................ 5
Changes to Table 14 and Table 15 ................................................ 32
Added Power Supply Configuration Section and Figure 56 ..... 33
Changes to Ordering Guide .......................................................... 34
6/06—Rev. 0 to Rev. A
Changes to Table 1.............................................................................1
Changes to Specifications .................................................................3
Added Thermal Hysteresis to Terminology Section.................. 14
Change to Figure 42 ....................................................................... 20
Change to Control Register Section............................................. 23
10/05—Revision 0: Initial Version
Rev. C | Page 2 of 36
Data Sheet
SPECIFICATIONS
AD7328
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
. With V
CC
< 4.75 V, all specifications are typical.
Table 2.
Parameter
DYNAMIC PERFORMANCE
Signal-to-Noise Ratio (SNR)
1
Min
76
72.5
75
B Version
Typ
Max
Unit
dB
dB
dB
Signal-to-Noise and Distortion
(SINAD)
2
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
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
4
−80
−80
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
−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 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
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
Differential mode
Single-ended/pseudo differential mode
Differential mode
Single-ended/pseudo differential mode
Single-ended/pseudo differential mode (LSB = FSR/8192)
Integral Nonlinearity
2
Rev. C | Page 3 of 36
AD7328
Parameter
Differential Nonlinearity
2
1
Data Sheet
Min
B Version
Typ
Max
−0.9/+1.5
±0.9
−0.7/+1
Unit
LSB
LSB
LSB
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
When in track, ±10 V range
When in track, ±5 V and 0 V to +10 V ranges
When in track, ±2.5 V range
When in hold, all ranges
Offset Error
2, 5
Offset Error Match
2, 5
Gain Error
2, 5
Gain Error Match
2, 5
Positive Full-Scale Error
2, 6
Positive Full-Scale Error Match
2, 6
Bipolar Zero Code Error
2, 6
Bipolar Zero Code Error Match
2, 6
Negative Full-Scale Error
2, 6
Negative Full-Scale Error Match
2, 6
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
±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
±200
13.5
16.5
21.5
3
2.5
10
2.5
150
50
±5
±10
25
6
7
3
±1
V
V
V
V
nA
pF
pF
pF
pF
V
µA
pF
V
ppm
ppm
mV
mV
ppm/°C
ppm/°C
Ω
REFERENCE INPUT/OUTPUT
Input Voltage Range
Input DC Leakage Current
Input Capacitance
Reference Output Voltage
Long Term Stability
Output Voltage Hysteresis
Reference Output Voltage Error
at 25°C
Reference Output Voltage
T
MIN
to T
MAX
Reference Temperature Coefficient
Reference Output Impedance
For 1000 hours
Rev. C | Page 4 of 36
Data Sheet
Parameter
LOGIC INPUTS
Input High Voltage, V
INH
Input Low Voltage, V
INL
1
AD7328
Min
2.4
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
B Version
Typ
Max
Unit
V
V
V
µA
pF
V
V
µA
pF
Test Conditions/Comments
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
V
CC
= 4.75 V to 5.25 V
V
CC
= 2.7 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
V
CC
= 4.75 V to 5.25 V; see the Serial Interface section
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
For dc accuracy specifications, the LSB size for differential mode is FSR/8192. For single-ended mode/pseudo differential mode, the LSB size is FSR/4096, unless otherwise noted.
5
Unipolar 0 V to 10 V range with straight binary output coding.
6
Bipolar range with twos complement output coding.
Rev. C | Page 5 of 36
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