8-Channel, I2C, 12-Bit SAR ADC
with Temperature Sensor
AD7291-EP
FEATURES
FUNCTIONAL BLOCK DIAGRAM
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 VDD of 2.8 V to 3.6 V
Logic voltage VDRIVE = 1.65 V to 3.6 V
Internal 2.5 V reference
I2C-compatible serial interface supports standard and
fast speed modes
Out of range indicator/alert function
Autocycle mode
Power-down current: 13 µA maximum
20-lead LFCSP package
VDD
ENHANCED PRODUCT FEATURES
GND
VREF
REF
12-BIT
SUCCESSIVE
APPROXIMATION
ADC
VIN0
T/H
VIN7
INPUT
MUX
AD7291-EP
SEQUENCER
CONTROL LOGIC
I2C INTERFACE
TEMP
SENSOR
SCL
SDA
AS1
AS0
VDRIVE
PD/RST
Supports defense and aerospace applications (AQEC
standard)
Extended industrial temperature range: −55°C to +125°C
Controlled manufacturing baseline
1 assembly/test site
1 fabrication site
Product change notification
Qualification data available upon request
BUF
ALERT
15915-001
Enhanced Product
Figure 1.
GENERAL DESCRIPTION
The AD7291-EP is a 12-bit, low power, 8-channel, successive
approximation analog-to-digital converter (ADC) with an
internal temperature sensor.
The AD7291-EP 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 device operates from a single 3.3 V power supply and
features an I2C-compatible interface. The device contains a
9-channel multiplexer and a track-and-hold amplifier with an
input bandwidth of 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-EP offers a programmable sequencer, which
enables the selection of a preprogrammable sequence of
channels for conversion.
The AD7291-EP provides a 2-wire serial interface compatible
with I2C interfaces. The I2C interface supports standard and fast
I2C interface modes. The AD7291-EP 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 I2C write
operations or an autocycle mode selected through software control.
Rev. 0
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.
Additional application and technical information can be found
in the AD7291 data sheet.
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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
©2017 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
AD7291-EP
Enhanced Product
TABLE OF CONTENTS
Features .............................................................................................. 1
Thermal Resistance .......................................................................5
Enhanced Product Features ............................................................ 1
ESD Caution...................................................................................5
Functional Block Diagram .............................................................. 1
Pin Configuration and Function Descriptions..............................6
General Description ......................................................................... 1
Typical Performance Characteristics ..............................................7
Revision History ............................................................................... 2
Outline Dimensions ..........................................................................8
Specifications..................................................................................... 3
Ordering Guide .............................................................................8
Absolute Maximum Ratings ............................................................ 5
REVISION HISTORY
7/2017—Revision 0: Initial Version
Rev. 0 | Page 2 of 8
Enhanced Product
AD7291-EP
SPECIFICATIONS
VDD = 2.8 V to 3.6 V; VDRIVE = 1.65 V to 3.6 V; fSCL = 400 kHz, fast SCLK mode; VREF = 2.5 V internal/external; TA = −55°C to +125°C,
unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
Signal-to-Noise Ratio (SNR)
Signal-to-Noise + Distortion Ratio (SINAD)
Total Harmonic Distortion (THD)
Spurious-Free Dynamic Range (SFDR)
Intermodulation Distortion (IMD)
Second-Order Terms
Third-Order Terms
Channel-to-Channel Isolation
Full Power Bandwidth 2
DC ACCURACY
Resolution
Integral Nonlinearity (INL)
Differential Nonlinearity (DNL)
Offset Error
Offset Error Matching
Offset Temperature Drift
Gain Error
Gain Error Matching
Gain Temperature Drift
ANALOG INPUT
Input Voltage Ranges
DC Leakage Current
Input Capacitance2
REFERENCE INPUT/OUTPUT
Reference Output Voltage 3
Long-Term Stability
Output Voltage Hysteresis
Reference Input Voltage Range 4
DC Leakage Current
VREF Output Impedance
Reference Temperature Coefficient
VREF Noise2
LOGIC INPUTS (SDA, SCL)
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN2
Input Hysteresis, VHYST
Min
Typ
70
70
71
71
−84
−85
Max
Unit 1
−78
−80
dB
dB
dB
dB
Test Conditions/Comments
fIN = 1 kHz sine wave
fA = 5.4 kHz, fB = 4.6 kHz
−88
−88
−100
30
10
dB
dB
dB
MHz
MHz
12
±0.5
±0.5
±2
±2.5
4
±1
±1
0.5
0
±0.01
34
8
2.4925
2.5
150
50
1
±0.01
1
12
60
±1
±0.99
±4.5
±4.5
±4
±2.5
VREF
±1
2.5075
2.5
±1
35
0.7 × VDRIVE
±0.01
6
0.3 × VDRIVE
±1
0.1 × VDRIVE
Rev. 0 | Page 3 of 8
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
fIN = 10 kHz
At 3 dB
At 0.1 dB
Guaranteed no missing codes to 12 bits
When in track
When in hold
±0.3% maximum at 25°C
For 1000 hours
External reference applied to Pin VREF
Bandwidth = 10 MHz
VIN = 0 V or VDRIVE
AD7291-EP
Parameter
LOGIC OUTPUTS
Output High Voltage, VOH
Enhanced Product
Min
Typ
VDRIVE − 0.3
VDRIVE − 0.2
Output Low Voltage, VOL
Floating State Leakage Current
Floating State Output Capacitance2
INTERNAL TEMPERATURE SENSOR
Operating Range
Accuracy
Resolution
CONVERSION RATE
Conversion Time
Autocycle Update Rate 5
Throughput Rate
POWER REQUIREMENTS
VDD
VDRIVE
ITOTAL 6, 7
Normal Mode (Operational)
Normal Mode (Static)
Full Power-Down Mode
Power Dissipation 7
Normal Mode (Operational)
Normal Mode (Static)
Full Power-Down Mode
Max
±0.01
8
−55
±1
±1
0.25
0.4
0.6
±1
+125
±2
±3
3.2
50
2.8
1.65
Unit 1
Test Conditions/Comments
V
V
V
V
µA
pF
VDRIVE < 1.8
VDRIVE ≥ 1.8
ISINK = 3 mA
ISINK = 6 mA
°C
°C
°C
°C
22.22
μs
μs
kSPS
3
3
3.6
3.6
V
V
2.9
2.9
0.3
1.6
4.9
3.5
3.4
1.6
4.5
13
mA
mA
μA
μA
μA
8.7
10.4
10.4
1.1
5.8
17.6
10.5
12.6
12.2
5.8
16.2
46.8
mW
mW
mW
µW
µW
µW
TA = −55°C to +85°C
TA = 85°C to 125°C
LSB size
fSCL = 400 kHz
Digital inputs = 0 V or VDRIVE
TA = −55°C to +25°C
TA = >25°C to 85°C
TA = >85°C to 125°C
VDD = 3 V, VDRIVE = 3 V
TA = −55°C to +25°C
TA = >25°C to 85°C
TA = >85°C to 125°C
All specifications expressed in decibels are referred to full-scale range (FSR) and tested with an input signal at 0.5 dB below full scale, unless otherwise specified.
Sample tested during initial product release to ensure compliance.
3
Refers to Pin VREF specified for 25oC.
4
A correction factor can be required on the temperature sensor results when using an external VREF (see the AD7291 data sheet).
5
Sampled during initial product release to ensure compliance; not subject to production testing.
6
ITOTAL is the total current flowing in VDD and VDRIVE.
7
ITOTAL and power dissipation are specified with VDD = VDRIVE = 3.6 V, unless otherwise noted.
1
2
Rev. 0 | Page 4 of 8
Enhanced Product
AD7291-EP
ABSOLUTE MAXIMUM RATINGS
THERMAL RESISTANCE
Table 2.
Parameter
VDD to GND1, GND
VDRIVE to GND1, GND
Analog Input Voltage to GND1
Digital Input Voltage to GND1
Digital Output Voltage to GND1
VREF to GND1
GND to GND1
Input Current to Any Pin Except Supplies1
Operating Temperature Range
Storage Temperature Range
Junction Temperature
Pb-free Temperature, Soldering
Reflow
ESD
1
Rating
−0.3 V to +5 V
−0.3 V to +5 V
−0.3 V to +3 V
−0.3 V to VDRIVE + 0.3 V
−0.3 V to VDRIVE + 0.3 V
−0.3 V to +3 V
−0.3 V to +0.3 V
±10 mA
−55°C to +125°C
−65°C to +150°C
150°C
Thermal performance is directly linked to printed circuit board
(PCB) design and operating environment. Close attention to
PCB thermal design is required.
Table 3. Thermal Resistance
Package Type
CP-20-81
1
θJA
52
θJC
6.5
Unit
°C/W
Thermal impedance simulated values are based on JEDEC 2S2P thermal test
board with 9 thermal vias. See JEDEC JESD51.
ESD CAUTION
260(+0)°C
2 kV
Transient currents of up to 100 mA do not cause latch-up.
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Rev. 0 | Page 5 of 8
AD7291-EP
Enhanced Product
16 VDRIVE
18 VIN0
17 PD/RST
20 VIN2
19 VIN1
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VIN3 1
15 SCL
VIN4 2
14 SDA
AD7291-EP
VIN5 3
13 AS1
TOP VIEW
(Not to Scale)
VIN6 4
12 ALERT
11 AS0
NOTES
1. THE EXPOSED METAL PADDLE ON THE BOTTOM
OF THE LFCSP PACKAGE SHOULD BE SOLDERED
TO PCB GROUND FOR PROPER HEAT DISSIPATION
AND PERFORMANCE.
15915-002
VDD 10
GND 9
DCAP 8
VREF 7
GND1 6
VIN7 5
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
1 to 5,
18 to 20
6
Mnemonic
VIN3, VIN4,
VIN5, VIN6,
VIN7, VIN0,
VIN1, VIN2
GND1
7
VREF
8
DCAP
9
GND
10
11, 13
VDD
AS0, AS1
12
ALERT
14
SDA
15
SCL
16
VDRIVE
17
PD/RST
EPAD
EPAD
Description
Analog Inputs. The AD7291-EP has eight single-ended analog inputs that are multiplexed into the on-chip trackand-hold amplifier. Each input channel can accept analog inputs from 0 V to 2.5 V. Any unused input channels
must be connected to GND1 to avoid noise pickup.
Ground. Ground reference point for the internal reference circuitry on the AD7291-EP. All analog input signals and
the external reference signals must be referred to this GND1 voltage. The GND1 pin must be connected to the
ground plane of a system. All ground pins must ideally be at the same potential and must not be more than 0.3 V
apart, even on a transient basis. The VREF pin must be decoupled to this ground pin via a 10 μF decoupling capacitor.
Internal Reference/External Reference Supply. The nominal internal reference voltage of 2.5 V appears at this pin.
Provided the output is buffered, the on-chip reference can be taken from this pin and applied externally to the rest
of a system. Decoupling capacitors must be connected to this pin to decouple the reference buffer. For best
performance, it is recommended to use a 10 μF decoupling capacitor on this pin to GND1. The internal reference
can be disabled and an external reference supplied to this pin if required. The input voltage range for the external
reference is 2.0 V to 2.5 V.
Decoupling Capacitor Pin. Decoupling capacitors (1 μF recommended) are connected to this pin to decouple the
internal low dropout regulator (LDO).
Ground. Ground reference point for all analog and digital circuitry on the AD7291-EP. The GND pin must be connected to the ground plane of the system. All ground pins must ideally be at the same potential and must not be
more than 0.3 V apart, even on a transient basis. Both DCAP and VDD pins must be decoupled to this GND pin.
Supply Voltage, 2.8 V to 3.6 V. This supply must be decoupled to GND with 10 μF and 100 nF decoupling capacitors.
Logic Inputs. Together, the logic state of these two inputs selects a unique I2C address for the AD7291-EP. See the
AD7291 data sheet for details. The device address depends on the voltage applied to these pins.
Digital Output. This pin acts as an out-of-range indicator and, if enabled, becomes active when the conversion
result violates the DATAHIGH or DATALOW register values. See the AD7291 data sheet for further details.
Digital Input/Output. Serial bus bidirectional data. This open-drain output requires a pull-up resistor. The output
coding is straight binary for the voltage channels and twos complement for the temperature sensor result.
Digital Inputs. Serial I2C Bus Clock. This input requires a pull-up resistor. The data transfer rate in I2C mode is
compatible with both 100 kHz and 400 kHz operating modes.
Logic Power Supply Input. The voltage supplied at this pin determines the voltage at which the interface operates.
This pin must be decoupled to GND. The voltage range on this pin is 1.65 V to 3.6 V and can be less than the
voltage at VDD but must never exceed it by more than 0.3 V.
Power-Down Pin. This pin places the device into a full power-down mode and enables power conservation when
operation is not required. This pin can be used to reset the device by toggling the pin low for a minimum of 1 ns and a
maximum of 100 ns. If the maximum time is exceeded, the device enters power-down mode. When placing the device
in full power-down mode, the analog inputs must be returned to 0 V.
Exposed Pad. The exposed metal paddle on the bottom of the LFCSP package must be soldered to PCB ground for
proper functionality and heat dissipation.
Rev. 0 | Page 6 of 8
Enhanced Product
AD7291-EP
TYPICAL PERFORMANCE CHARACTERISTICS
1.5
7
VDRIVE = 3V
6
TOTAL CURRENT (µA)
0.5
0
–0.5
–1.0
5
4
–55°C
+25°C
+85°C
+125°C
3
2
–1.5
–55 –40 –25 –10
5
20
35
55
65
80
TEMPERATURE (°C)
Figure 3. Temperature Accuracy at 3 V
95
110 125
0
2.7
2.8
2.9
3.0
3.1
3.2
VDD (V)
3.3
3.4
3.5
3.6
15915-004
1
15915-003
TEMPERATURE ERROR (°C)
1.0
Figure 4. Full Shutdown Current vs. Supply Voltage for Various Temperatures
Rev. 0 | Page 7 of 8
AD7291-EP
Enhanced Product
OUTLINE DIMENSIONS
DETAIL A
(JEDEC 95)
4.10
4.00 SQ
3.90
16
0.50
BSC
PIN 1
INDIC ATOR AREA OPTIONS
(SEE DETAIL A)
20
1
15
2.75
2.60 SQ
2.35
EXPOSED
PAD
5
11
TOP VIEW
0.80
0.75
0.70
SIDE VIEW
PKG-005089
SEATING
PLANE
0.50
0.40
0.30
10
6
BOTTOM VIEW
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.20 REF
0.25 MIN
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
COMPLIANT TO JEDEC STANDARDS MO-220-WGGD-11.
02-21-2017-B
PIN 1
INDICATOR
0.30
0.25
0.18
Figure 5. 20-Lead Lead Frame Chip Scale Package [LFCSP]
4 mm × 4 mm Body and 0.75 mm Package Height
(CP-20-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model 1
AD7291TCPZ-EP
AD7291TCPZ-EP-RL7
1
Temperature Range
−55°C to +125°C
−55°C to +125°C
Package Description
20-Lead Lead Frame Chip Scale Package [LFCSP]
20-Lead Lead Frame Chip Scale Package [LFCSP]
Z = RoHS Compliant Part.
I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).
©2017 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D15915-0-7/17(0)
Rev. 0 | Page 8 of 8
Package Option
CP-20-8
CP-20-8