Data Sheet
FEATURES
12-bit SAR ADC
8 single-ended analog input channels
Analog input range: 0 V to 2.5 V
12-bit temperature-to-digital converter
Temperature sensor accuracy of ±1°C typical
Channel sequencer operation
Specified for V
DD
of 2.8 V to 3.6 V
Logic voltage V
DRIVE
= 1.65 V to 3.6 V
Internal 2.5 V reference
I
2
C-compatible serial interface supports standard and
fast speed modes
Out of range indicator/alert function
Autocycle mode
Power-down current: 12 μA maximum
Temperature range: −40°C to +125°C
20-lead LFCSP package
8-Channel, I
2
C, 12-Bit SAR ADC
with Temperature Sensor
AD7291
FUNCTIONAL BLOCK DIAGRAM
V
DD
GND
V
REF
REF
BUF
V
IN0
T/H
12-BIT
SUCCESSIVE
APPROXIMATION
ADC
V
IN7
INPUT
MUX
AD7291
SEQUENCER
CONTROL LOGIC
I
2
C INTERFACE
TEMP
SENSOR
SCL
SDA
AS1
AS0
V
DRIVE
PD/RST
ALERT
Figure 1.
GENERAL DESCRIPTION
The AD7291 is a 12-bit, low power, 8-channel, successive
approximation analog-to-digital converter (ADC) with an
internal temperature sensor.
The device operates from a single 3.3 V power supply and
features an I
2
C-compatible interface. The device contains a 9-
channel multiplexer and a track-and-hold amplifier than can
handle frequencies up to 30 MHz. The device has an on-chip
2.5 V reference that can be disabled to allow the use of an
external reference.
The AD7291 provides a 2-wire serial interface compatible with
I
2
C interfaces. The I
2
C interface supports standard and fast I
2
C
interface modes. The AD7291 normally remains in a partial
power-down state while not converting and powers up for
conversions. The conversion process can be controlled by a
command mode where conversions occur across I
2
C write
operations or an autocycle mode selected through software
control.
The AD7291 includes a high accuracy band gap temperature
sensor, which is monitored and digitized by the 12-bit ADC to
give a resolution of 0.25°C.
The AD7291 offers a programmable sequencer, which enables
the selection of a preprogrammable sequence of channels for
conversion.
On-chip limit registers can be programmed with high and low
limits for the conversion results; an out-of-range indicator
output (ALERT) becomes active when the programmed high
or low limits are violated by the conversion result. This output
can be used as an interrupt.
PRODUCT HIGHLIGHTS
1.
Ideally suited to monitoring system variables in a variety
of systems including telecommunications, process control,
and industrial control.
I
2
C-compatible serial interface, which supports standard
and fast modes.
Automatic partial power-down while not converting to
maximize power efficiency.
Channel sequencer operation.
Integrated temperature sensor with 0.25°C resolution.
Out of range indicator that can be software disabled or
enabled.
2.
3.
4.
5.
6.
Table 1. AD7291 and Related Products
Device
AD7291
AD7298
Resolution
12-bit
12-bit
Interface
I
2
C
SPI
Features
8-channel, I
2
C, 12-bit SAR
ADC with temperature sensor
8-channel, 1 MSPS, 12-bit SAR
ADC with temperature sensor
Rev. C
Document Feedback
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2011–2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
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.
08711-001
AD7291* PRODUCT PAGE QUICK LINKS
Last Content Update: 09/07/2017
COMPARABLE PARTS
View a parametric search of comparable parts.
REFERENCE MATERIALS
Technical Articles
•
MS-2210: Designing Power Supplies for High Speed ADC
Tutorials
•
Integrated SAR ADC Family in 4mm x 4mm Package
EVALUATION KITS
•
AD7291 Evaluation Board
•
AD9361 Software Defined Radio Board (2.4GHz
Optimized)
•
AD9361 Wideband Software Defined Radio Board
•
AD9364 Wideband Software Defined Radio Board
•
ADA4961 & AD9680 Analog Signal Chain Evaluation and
AD9528 Converter Synchronization
•
ADL5567 & AD9625 Analog Signal Chain Evaluation and
ADF4355-2 Wideband Synthesizer with VCO
DESIGN RESOURCES
•
AD7291 Material Declaration
•
PCN-PDN Information
•
Quality And Reliability
•
Symbols and Footprints
DISCUSSIONS
View all AD7291 EngineerZone Discussions.
DOCUMENTATION
Data Sheet
•
AD7291-DSCC: Military Data Sheet
•
AD7291-EP: Enhanced Product Data Sheet
•
AD7291: 8-Channel, I
2
C, 12-Bit SAR ADC with Temperature
Sensor Data Sheet
User Guides
•
UG-253: Evaluation Board for the AD7291, 8-Channel, I
2
C,
12-Bit SAR ADC with Temperature Sensor
SAMPLE AND BUY
Visit the product page to see pricing options.
TECHNICAL SUPPORT
Submit a technical question or find your regional support
number.
DOCUMENT FEEDBACK
Submit feedback for this data sheet.
SOFTWARE AND SYSTEMS REQUIREMENTS
•
AD7291 - Microcontroller No-OS Driver
•
AD7291 IIO ADC Linux Driver
•
AD7291 Evaluation Software
•
AD7291 FMC-SDP Interposer & Evaluation Board / Xilinx
KC705 Reference Design
•
BeMicro FPGA Project for AD7291 with Nios driver
This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not
trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.
AD7291
TABLE OF CONTENTS
Features .............................................................................................. 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
I
2
C Timing Specifications ............................................................ 5
Absolute Maximum Ratings............................................................ 6
Thermal Resistance ...................................................................... 6
ESD Caution .................................................................................. 6
Pin Configuration and Function Descriptions ............................. 7
Typical Performance Characteristics ............................................. 8
Terminology .................................................................................... 11
Circuit Information ........................................................................ 12
Converter Operation .................................................................. 12
Analog Input ............................................................................... 12
ADC Transfer Function ............................................................. 13
Temperature Sensor Operation ................................................ 13
Temperature Sensor Averaging................................................. 13
V
DRIVE
............................................................................................ 14
The Internal or External Reference .......................................... 14
Reset ............................................................................................. 14
Internal Register Structure ............................................................ 15
Data Sheet
Address Pointer Register ........................................................... 15
Command Register (0x00) ........................................................ 17
Voltage Conversion Result Register (0x01) ............................ 18
T
SENSE
Conversion Result Register (0x02) ................................ 18
T
SENSE
Average Result Register (0x03) ...................................... 19
Limit Registers (0x04 to 0x1E) ................................................. 19
Hysteresis Register ..................................................................... 20
Alert Status Register A and Alert Status Register B (0x1F and
0x20)............................................................................................. 20
I
2
C Interface .................................................................................... 21
Serial Bus Address Byte ............................................................. 21
General I
2
C Timing .................................................................... 21
Writing to the AD7291 .................................................................. 22
Writing Two Bytes of Data to a 16-Bit Register ..................... 22
Writing to Multiple Registers.................................................... 22
Reading Data From the AD7291 .................................................. 23
Reading Two Bytes of Data from a 16-Bit Register ............... 23
Modes of Operation ....................................................................... 24
Command Mode ........................................................................ 24
Autocycle Mode .......................................................................... 26
Outline Dimensions ....................................................................... 27
Ordering Guide .......................................................................... 27
REVISION HISTORY
10/2016—Rev. B to Rev. C
Changes to Command Mode Section .......................................... 25
10/2011—Rev. A to Rev. B
Changes to Table 9 .......................................................................... 16
8/2011—Rev. 0 to Rev. A
Changes to Temperature Sensor—Internal, Accuracy Parameter,
Table 2 ................................................................................................ 3
1/2011—Revision 0: Initial Version
Rev. C | Page 2 of 28
Data Sheet
SPECIFICATIONS
AD7291
V
DD
= 2.8 V to 3.6 V; V
DRIVE
= 1.65 V to 3.6 V; f
SCL
= 400 kHz, fast SCLK mode; V
REF
= 2.5 V internal/external; T
A
= −40°C to +125°C,
unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
Signal-to-Noise Ratio (SNR)
2
Signal-to-Noise (+ Distortion) Ratio (SINAD)
2
Total Harmonic Distortion (THD)
2
Spurious-Free Dynamic Range (SFDR)
Intermodulation Distortion (IMD)
Second-Order Terms
Third-Order Terms
Channel-to-Channel Isolation
Full Power Bandwidth
3
DC ACCURACY
Resolution
Integral Nonlinearity (INL)
2
Differential Nonlinearity (DNL)
2
Offset Error
2
Offset Error Matching
2
Offset Temperature Drift
Gain Error
2
Gain Error Matching
2
Gain Temperature Drift
ANALOG INPUT
Input Voltage Ranges
DC Leakage Current
Input Capacitance
3
REFERENCE INPUT/OUTPUT
Reference Output Voltage
4
Long-Term Stability
Output Voltage Hysteresis
Reference Input Voltage Range
5
DC Leakage Current
V
REF
Output Impedance
Reference Temperature Coefficient
V
REF
Noise
3
LOGIC INPUTS (SDA, SCL)
Input High Voltage, V
INH
Input Low Voltage, V
INL
Input Current, I
IN
Input Capacitance, C
IN3
Input Hysteresis, V
HYST
LOGIC OUTPUTS
Output High Voltage, V
OH
Output Low Voltage, V
OL
Min
70
70
Typ
71
71
−84
−85
−88
−88
−100
30
10
12
±0.5
±0.5
±2
±2.5
4
±1
±1
0.5
0
±0.01
34
8
2.4925
2.5
150
50
±0.01
1
12
60
0.7 × V
DRIVE
±0.01
6
0.1 × V
DRIVE
V
DRIVE
− 0.3
V
DRIVE
− 0.2
0.4
0.6
0.3 × V
DRIVE
±1
±1
±0.99
±4.5
±4.5
±4
±2.5
Max
Unit
1
dB
dB
dB
dB
f
A
= 5.4 kHz, f
B
= 4.6 kHz
dB
dB
dB
MHz
MHz
Bits
LSB
LSB
LSB
LSB
ppm/°C
LSB
LSB
ppm/°C
V
µA
pF
pF
V
ppm
ppm
V
µA
Ω
ppm/°C
µV rms
V
V
µA
pF
V
V
V
V
V
Test Conditions/Comments
f
IN
= 1 kHz sine wave
−78
−80
f
IN
= 10 kHz
At 3 dB
At 0.1 dB
Guaranteed no missed codes to 12 bits
V
REF
±1
When in track
When in hold
±0.3% maximum at 25°C
For 1000 hours
2.5075
1
2.5
±1
35
External reference applied to Pin V
REF
Bandwidth = 10 MHz
V
IN
= 0 V or V
DRIVE
V
DRIVE
< 1.8
V
DRIVE
≥ 1.8
I
SINK
= 3 mA
I
SINK
= 6 mA
Rev. C | Page 3 of 28
AD7291
Parameter
Floating State Leakage Current
Floating State Output Capacitance
3
TEMPERATURE SENSOR—INTERNAL
Operating Range
Accuracy
Resolution
CONVERSION RATE
Conversion Time
Autocycle Update Rate
6
Throughput Rate
POWER REQUIREMENTS
V
DD
V
DRIVE
I
TOTAL 7, 8
Normal Mode (Operational)
Normal Mode (Static)
Full Power-Down Mode
Min
Typ
±0.01
8
Max
±1
Unit
1
µA
pF
°C
°C
°C
°C
μs
μs
kSPS
V
V
mA
mA
μA
μA
μA
mW
mW
mW
µW
µW
µW
Data Sheet
Test Conditions/Comments
−40
±1
±1
0.25
3.2
50
+125
±2
±3
T
A
= −40°C to +85°C
T
A
= 85°C to 125°C
LSB size
22.22
2.8
1.65
3
3
2.9
2.9
0.3
1.6
4.9
8.7
10.4
10.4
1.1
5.8
17.6
3.6
3.6
3.5
3.3
1.6
4.5
12
10.5
12.6
11.9
5.8
16.2
43.2
f
SCL
= 400 kHz
Digital inputs = 0 V or V
DRIVE
T
A
= −40°C to +25°C
T
A
= >25°C to 85°C
T
A
= >85°C to 125°C
V
DD
= 3 V, V
DRIVE
= 3 V
Power Dissipation
8
Normal Mode (Operational)
Normal Mode (Static)
Full Power-Down Mode
T
A
= −40°C to +25°C
T
A
= >25°C to 85°C
T
A
= >85°C to 125°C
All specifications expressed in decibels are referred to full-scale input, FSR, and tested with an input signal at 0.5 dB below full scale, unless otherwise specified.
See the Terminology section.
3
Sample tested during initial release to ensure compliance.
4
Refers to Pin
V
REF
specified for 25
o
C.
5
A correction factor can be required on the temperature sensor results when using an external V
REF
(see the Temperature Sensor Averaging section).
6
Sampled during initial release to ensure compliance; not subject to production testing.
7
I
TOTAL
is the total current flowing in V
DD
and V
DRIVE
.
8
I
TOTAL
and power dissipation are specified with V
DD
= V
DRIVE
= 3.6 V, unless otherwise noted.
1
2
Rev. C | Page 4 of 28
京公网安备 11010802033920号
EEWORLD
