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8-Channel, High Throughput,
24-Bit
∑
-∆ ADC
AD7739
FEATURES
High resolution ADC
24 bits no missing codes
±0.0015% nonlinearity
Optimized for fast channel switching
18-bit p-p resolution (21 bits effective) at 500 Hz
16-bit p-p resolution (19 bits effective) at 4 kHz
On-chip per channel system calibration
Configurable inputs
8 single-ended or 4 fully differential
Input ranges
+625 mV, ±625 mV, +1.25 V, ±1.25 V, +2.5 V, ±2.5 V
3-wire serial interface
SPI®, QSPI™, MICROWIRE™, and DSP compatible
Schmitt trigger on logic inputs
Single-supply operation
5 V analog supply
3 V or 5 V digital supply
Package: 24-lead TSSOP
FUNCTIONAL BLOCK DIAGRAM
REFIN(–)
REFIN(+)
REFERENCE
DETECT
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AINCOM/P0
CALIBRATION
CIRCUITRY
MUX
BUFFER
24-BIT
Σ-∆
ADC
AD7739
CS
SERIAL
INTERFACE
SCLK
DOUT
DIN
I/O PORT
SYNC/P1
CLOCK
GENERATOR
CONTROL
LOGIC
RESET
RDY
APPLICATIONS
PLCs/DCSs
Multiplexing applications
Process control
Industrial instrumentation
AGND
AV
DD
MCLKOUT MCLKIN DGND
DV
DD
03742-0-001
Figure 1.
GENERAL DESCRIPTION
The AD7739 is a high precision, high throughput analog front
end. True 16-bit p-p resolution is achievable with a total
conversion time of 250 µs (4 kHz channel switching), making it
ideally suited to high resolution multiplexing applications.
The part can be configured via a simple digital interface, which
allows users to balance the noise performance against data
throughput up to 15 kHz.
The analog front end features eight single-ended or four fully
differential input channels with unipolar or bipolar 625 mV,
1.25 V, and 2.5 V input ranges. It accepts a common-mode input
voltage from 200 mV above AGND to AV
DD
– 300 mV.
The differential reference input features “No-Reference” detect
capability. The ADC also supports per channel system
calibration options.
The digital serial interface can be configured for 3-wire
operation and is compatible with microcontrollers and digital
signal processors. All interface inputs are Schmitt triggered.
The part is specified for operation over the extended industrial
temperature range of –40°C to +105°C.
Other parts in the AD7739 family are the AD7738, AD7734,
and AD7732.
The AD7738 is similar to the AD7739 but has higher speed
(8.5 kHz channel switching for 16-bit performance) and higher
AIN leakage current. The AD7738 multiplexer output is pinned
out externally, allowing the user to implement programmable
gain or signal conditioning before being applied to the ADC.
The AD7734 analog front end features four single-ended input
channels with unipolar or true bipolar input ranges to ±10 V
while operating from a single +5 V analog supply. The AD7734
accepts an analog input overvoltage to ±16.5 V without
degrading the performance of the adjacent channels.
The AD7732 is similar to the AD7734, but its analog front end
features two fully differential input channels.
Rev. 0
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 companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
www.analog.com
Tel: 781.329.4700
Fax: 781.326.8703
© 2003 Analog Devices, Inc. All rights reserved.
AD7739
TABLE OF CONTENTS
AD7739—Specifications.................................................................. 3
Timing Specifications....................................................................... 6
Absolute Maximum Ratings............................................................ 8
Typical Performance Characteristics ............................................. 9
Output Noise and Resolution Specification................................ 10
Chopping Enabled...................................................................... 10
Chopping Disabled..................................................................... 11
Pin Configuration and Function Descriptions........................... 12
Register Descriptions ..................................................................... 14
Register Access............................................................................ 15
Communications Register......................................................... 15
I/O Port Register......................................................................... 16
Revision Register ........................................................................ 16
Test Register ................................................................................ 16
ADC Status Register................................................................... 17
Checksum Register..................................................................... 17
ADC Zero-Scale Calibration Register ..................................... 17
ADC Full-Scale Calibration Register....................................... 17
Channel Data Registers ............................................................. 17
Channel Zero-Scale Calibration Registers .............................. 18
Channel Full-Scale Calibration Registers................................ 18
Channel Status Registers ........................................................... 18
Channel Setup Registers ............................................................ 19
Channel Conversion Time Registers ....................................... 20
Mode Register ............................................................................. 20
Digital Interface Description ........................................................ 22
Hardware ..................................................................................... 22
Reset ............................................................................................. 23
Access the AD7739 Registers.................................................... 23
Single Conversion and Reading Data ...................................... 23
Dump Mode................................................................................ 23
Continuous Conversion Mode ................................................. 24
Continuous Read (Continuous Conversion) Mode .............. 25
Circuit Description......................................................................... 26
Analog Inputs.............................................................................. 26
Sigma-Delta ADC....................................................................... 26
Chopping ..................................................................................... 26
Multiplexer, Conversion, and Data Output Timing............... 27
Frequency Response .................................................................. 28
Analog Input’s Extended Voltage Range ................................. 29
Voltage Reference Inputs........................................................... 29
Reference Detect......................................................................... 29
I/O Port........................................................................................ 29
Calibration................................................................................... 30
ADC Zero-Scale Self-Calibration ........................................ 30
ADC Full-Scale Self-Calibration.......................................... 30
Per Channel System Calibration .......................................... 30
Outline Dimensions ....................................................................... 32
ESD Caution................................................................................ 32
Ordering Guide .......................................................................... 32
REVISION HISTORY
Revision 0: Initial Version
Rev. 0 | Page 2 of 32
AD7739
AD7739—SPECIFICATIONS
Table 1. (–40°C to +105°C; AV
DD
= 5 V ± 5%; DV
DD
= 2.7 V to 3.6 V, or 5 V ± 5%; REFIN(+) = 2.5 V; REFIN(–) = 0 V,
AINCOM = 2.5 V; Internal Buffer On, AIN Range = ±1.25 V; f
MCLKIN
= 6.144 MHz; unless otherwise noted.)
Parameter
ADC PERFORMANCE
CHOPPING ENABLED
Conversion Time Rate
No Missing Codes
1, 2
Output Noise
Resolution
Integral Nonlinearity (INL)
2
Offset Error (Unipolar, Bipolar)
3
Offset Drift vs. Temperature
1
Gain Error
3
Gain Drift vs. Temperature
1
Positive Full-Scale Error
3
Positive Full-Scale Drift vs. Temp.
1
Bipolar Negative Full-Scale Error
4
Common-Mode Rejection
Power Supply Rejection
ADC PERFORMANCE
CHOPPING DISABLED
Conversion Time Rate
No Missing Codes
1, 2
Output Noise
Resolution
Integral Nonlinearity (INL)
2
Offset Error (Unipolar, Bipolar)
5
Offset Drift vs. Temperature
Gain Error
3
Gain Drift vs. Temperature
Positive Full-Scale Error
3
Positive Full-Scale Drift vs. Temp.
Bipolar Negative Full-Scale Error
4
Common-Mode Rejection
Power Supply Rejection
ANALOG INPUTS
Analog Input Voltage
1, 6
±2.5 V Range
+2.5 V Range
±1.25 V Range
+1.25 V Range
±0.625 V Range
+0.625 V Range
AIN, AINCOM Common-Mode/
Absolute Voltage
1
Analog Input Slew Rate
1, 7
AIN, AINCOM Input Current
1, 8
Min
Typ
Max
Unit
Test Conditions/Comments
372
24
See Table 4
See Table 5
and Table 6
±5
±10
11840
Hz
Bits
Configure via Conv. Time Register
FW
≥
12 (Conversion Time
≥
290 µs)
±0.0015
±25
±0.2
±2.5
±0.2
±2.5
80
70
±0.0030
95
80
% of FSR
µV
nV/°C
%
ppm of FS/°C
% of FSR
ppm of FS/°C
% of FSR
dB
dB
Before Calibration
Before Calibration
Before Calibration
After Calibration
At DC, AIN = 1 V
At DC, AIN = 1 V
737
24
See Table 7
See Table 8
and Table 9
±0.0015
±1mV
±1.5
±0.2
±2.5
±0.2
±2.5
±0.0030
75
65
15133
Hz
Bits
Configure via Conv. Time Register
FW
≥
12 (Conversion Time
≥
290 µs)
% of FSR
mV
µV/°C
%
ppm of FS/°C
% of FSR
ppm of FS/°C
% of FSR
dB
dB
Before Calibration
Before Calibration
Before Calibration
After Calibration
At DC, AIN = 1 V
At DC, AIN = 1 V
±2.5
0 to +2.5
±1.25
0 to +1.25
±0.625
0 to +0.625
0.2
AV
DD
– 0.3
0.5
5
V
V
V
V
V
V
V
V/Conv. Time
nA
AIN Absolute Voltage > 3 V
Only One Channel, Chop Disabled
1
Rev. 0 | Page 3 of 32
AD7739
Parameter
REFERENCE INPUTS
REFIN(+) to REFIN(–) Voltage
1, 9
NOREF Trigger Voltage
REFIN(+), REFIN(–) Common-Mode/
Absolute Voltage
1
Reference Input DC Current
10
SYSTEM CALIBRATION
1, 11
Full-Scale Calibration Limit
Zero-Scale Calibration Limit
Input Span
LOGIC INPUTS
Input Current
Input Current CS
Input Capacitance
V
T+1
V
T–1
V
T+
– V
T–1
V
T+1
V
T– 1
V
T+
– V
T–1
MCLK IN ONLY
Input Current
Input Capacitance
V
INL
Input Low Voltage
V
INH
Input High Voltage
V
INL
Input Low Voltage
V
INH
Input High Voltage
LOGIC OUTPUTS
12
V
OL
Output Low Voltage
V
OH
Output High Voltage
V
OL
Output Low Voltage
V
OH
Output High Voltage
Floating State Leakage Current
Floating State Leakage Capacitance
P0, P1 INPUTS/OUTPUTS
Input Current
V
INL
Input Low Voltage
V
INH
Input High Voltage
V
OL
Output Low Voltage
V
OH
Output High Voltage
5
1.4
0.8
0.3
0.95
0.4
0.3
2
1.4
0.85
2
1.1
0.85
±10
5
0.8
3.5
0.4
2.5
0.4
4.0
0.4
DV
DD
– 0.6
±1
3
±10
0.8
3.5
0.4
4.0
Min
2.475
0
Typ
2.5
0.5
Max
2.525
AV
DD
400
+1.05
×
FS
–1.05
×
FS
0.8
×
FS
2.1
×
FS
±1
±10
–40
Unit
V
V
V
µA
V
V
V
µA
µA
µA
pF
V
V
V
V
V
V
µA
pF
V
V
V
V
V
V
V
V
µA
pF
µA
V
V
V
V
Test Conditions/Comments
NOREF Bit in Channel Status Register
CS = DV
DD
CS = DGND, Internal Pull-Up Resistor
DV
DD
= 5 V
DV
DD
= 5 V
DV
DD
= 5 V
DV
DD
= 3 V
DV
DD
= 3 V
DV
DD
= 3 V
DV
DD
= 5 V
DV
DD
= 5 V
DV
DD
= 3 V
DV
DD
= 3 V
I
SINK
= 800 µA, DV
DD
= 5 V
I
SOURCE
= 200 µA, DV
DD
= 5 V
I
SINK
= 100 µA, DV
DD
= 3 V
I
SOURCE
= 100 µA, DV
DD
= 3 V
Levels Referenced to Analog Supplies
AV
DD
= 5 V
AV
DD
= 5 V
I
SINK
= 8 mA, AV
DD
= 5 V
I
SOURCE
= 200 µA, AV
DD
= 5 V
Rev. 0 | Page 4 of 32
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