ANALOG DEVICES AD8231-EP Service Manual

Zero Drift, Digitally Programmable

A

FEATURES

Digitally/pin-programmable gain

G = 1, 2, 4, 8, 16, 32, 64, or 128

Specified from −55°C to +125°C

50 nV/°C maximum input offset drift 10 ppm/°C maximum gain drift

Excellent dc performance

80 dB minimum CMR, G = 1 15 µV maximum input offset voltage 500 pA maximum bias current

0.7 µV p-p noise (0.1 Hz to 10 Hz)

Good ac performance

2.7 MHz bandwidth, G = 1

1.1 V/s slew rate Rail-to-rail output Shutdown/multiplex Extra op amp Single-supply range: 3 V to 6 V Dual-supply range: ±1.5 V to ±3 V

ENHANCED PRODUCT FEATURES

Supports defense and aerospace applications (AQEC

standard) Military temperature range (−55°C to +125°C) Controlled manufacturing baseline One assembly/test site One fabrication site Enhanced product change notification Qualification data available on request

Instrumentation Amplifier

AD8231-EP

FUNCTIONAL BLOCK DIAGRAM

A216A115A014CS

13

1

NC

LOGIC

2

–INA

+IN

NC

3

4

IN-AMP

AD8231-EP

5

SDN

OP

AMP

6

+INB

Figure 1.

7

–INB

Table 1. Instrumentation and Difference Amplifiers by Category

High Performance

AD8221 AD6231 AD628 AD620 AD6271 AD82311 AD82201 AD85531 AD629 AD621 AD8250 AD8222 AD524 AD8251 AD82241 AD526 AD85551

AD624 AD85561 AD85571

1

Rail-to-rail output.

Low Cost

High Voltage

Mil Grade

12

+V

S

11

–V

S

10

OUTA

9

REF

8

09707-001

OUTB

Low Power

Digital Gain

GENERAL DESCRIPTION

The AD8231-EP is a low drift, rail-to-rail, instrumentation amplifier with software-programmable gains of 1, 2, 4, 8, 16, 32, 64, or 128. The gains are programmed via digital logic or pin strapping.

The AD8231-EP is ideal for applications that require precision performance over a wide temperature range, such as industrial temperature sensing and data logging. Because the gain setting resistors are internal, maximum gain drift is only 10 ppm/°C for gains of 1 to 32. Because of the auto-zero input stage, maximum input offset is 15 μV and maximum input offset drift is just 50 nV/°C. CMRR is 80 dB for G = 1, increasing to 110 dB at higher gains.

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her 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.

The AD8231-EP also includes an uncommitted op amp that can be used for additional gain, differential signal driving, or filtering. Like the in-amp, the op amp has an auto-zero architecture, railto-rail input, and rail-to-rail output.

The AD8231-EP includes a shutdown feature that reduces current to a maximum of 1 μA. In shutdown, both amplifiers also have a high output impedance, which allows easy multiplexing of multiple amplifiers without additional switches.

The AD8231-EP is specified over the military temperature range of −55°C to +125°C. It is available in a 4 mm × 4 mm 16lead LFCSP.

Additional application and technical information can be found in the AD8231 data sheet.

AD8231-EP

REVISION HISTORY

5/11—Revision 0: Initial Version

ESD Caution...................................................................................7

Pin Configuration and Function Descriptions..............................8

Typical Performance Characteristics ..............................................8

Instrumentation Amplifier Performance Curves......................9

Operational Amplifier Performance Curves .......................... 15

Performance Curves Valid for Both Amplifiers ..................... 17

Outline Dimensions....................................................................... 18

Ordering Guide .......................................................................... 18

Rev. 0 | Page 2 of 20

AD8231-EP

SPECIFICATIONS

VS = 5 V, V

Table 2.

Parameter Test Conditions/Comments Min Typ Max Unit

INSTRUMENTATION AMPLIFIER

Offset Voltage VOS RTI = V

Input Offset, V

Output Offset, V

Input Currents

Input Bias Current 250 500 pA

T

Input Offset Current 20 100 pA

T

Gains 1, 2, 4, 8, 16, 32, 64, or 128

Gain Error

Gain Drift TA = −55°C to +125°C

Linearity 0.2 V to 4.8 V, 10 kΩ load 3 ppm

CMRR

G = 1 80 dB G = 2 86 dB G = 4 92 dB G = 8 98 dB G = 16 104 dB G = 32 110 dB G = 64 110 dB G = 128 110 dB

Noise en = √(e

Input Voltage Noise, eni f = 1 kHz 32 nV/√Hz f = 1 kHz, TA = −55°C 27 nV/√Hz f = 1 kHz, TA = 125°C 39 nV/√Hz f = 0.1 Hz to 10 Hz 0.7 μV p-p

Output Voltage Noise, eno f = 1 kHz 58 nV/√Hz f = 1 kHz, TA = −55°C 50 nV/√Hz f = 1 kHz, TA = 125°C 70 nV/√Hz f = 0.1 Hz to 10 Hz 1.1 μV p-p

Current Noise f = 10 Hz 20 fA/√Hz Other Input Characteristics

Common-Mode Input Impedance 10||5 GΩ||pF

Power Supply Rejection Ratio 100 115 dB

Input Operating Voltage Range 0.05 4.95 V Reference Input

Input Impedance

Voltage Range

= 2.5 V, G = 1, RL = 10 kΩ, TA = 25°C, unless otherwise noted.

REF

+ V

OSI

4 15 μV

OSI

/G

OSO

Average Temperature Drift TA = −55°C to +125°C 0.01 0.05 μV/°C

15 30 μV

OSO

Average Temperature Drift TA = −55°C to +125°C 0.05 0.5 μV/°C

= −55°C to +125°C 5 nA

A

= −55°C to +125°C 0.5 nA

A

G = 1 0.05 % G = 2 to 128 0.8 %

G = 1 to 32 3 10 ppm/°C G = 64 4 20 ppm/°C G = 128 10 30 ppm/°C

0.2 V to 4.8 V, 2 kΩ load 5 ppm

2

+ (eno/G)2), V

ni

IN+

, V

= 2.5 V

IN−

28 kΩ

−0.2 +5.2 V

Rev. 0 | Page 3 of 20

AD8231-EP

Parameter Test Conditions/Comments Min Typ Max Unit

Dynamic Performance

Bandwidth

G = 1 2.7 MHz G = 2 2.5 MHz

Gain Bandwidth Product

G = 4 to 128 7 MHz

Slew Rate 1.1 V/μs

Output Characteristics

Output Voltage High RL = 100 kΩ to ground 4.9 4.94 V R

= 10 kΩ to ground 4.8 4.88 V

L

Output Voltage Low RL = 100 kΩ to 5 V 60 100 mV R

= 10 kΩ to 5 V 80 200 mV

L

Short-Circuit Current 70 mA

Digital Interface

Input Voltage Low TA = −55°C to +125°C 1.0 V Input Voltage High TA = −55°C to +125°C 4.0 V

T

Setup Time to CS High Hold Time after CS High

= −55°C to +125°C 50 ns

A

T

= −55°C to +125°C 20 ns

A

OPERATIONAL AMPLIFIER

Input Characteristics

Offset Voltage, VOS 5 15 μV

Temperature Drift TA = −55°C to +125°C 0.01 0.06 μV/°C Input Bias Current 250 500 pA T

= −55°C to +125°C 5 nA

A

Input Offset Current 20 100 pA T

= −55°C to +125°C 0.5 nA

A

Input Voltage Range 0.05 4.95 V Open-Loop Gain 100 120 V/mV Common-Mode Rejection Ratio 100 120 dB Power Supply Rejection Ratio 100 110 dB Voltage Noise Density 20 nV/√Hz Voltage Noise f = 0.1 Hz to 10 Hz 0.4 μV p-p

Dynamic Performance

Gain Bandwidth Product 1 MHz Slew Rate 0.5 V/μs

Output Characteristics

Output Voltage High RL = 100 kΩ to ground 4.9 4.96 V R

= 10 kΩ to ground 4.8 4.92 V

L

Output Voltage Low RL = 100 kΩ to 5 V 60 100 mV R

= 10 kΩ to 5 V 80 200 mV

L

Short-Circuit Current 70 mA

BOTH AMPLIFIERS

Power Supply

Quiescent Current 4 5 mA Quiescent Current (Shutdown) 0.01 1 μA

Rev. 0 | Page 4 of 20

AD8231-EP

VS = 3.0 V, V

Table 3.

Parameter Conditions Min Typ Max Unit

INSTRUMENTATION AMPLIFIER

Offset Voltage VOS RTI = V

Average Temperature Drift 0.01 0.05 μV/°C

Average Temperature Drift 0.05 0.5 μV/°C

Input Currents

Input Bias Current 250 500 pA T Input Offset Current 20 100 pA T

Gains 1, 2, 4, 8, 16, 32, 64, or 128

Gain Error

Gain Drift TA = −55°C to +125°C

CMRR

G = 1 80 dB G = 2 86 dB G = 4 92 dB G = 8 98 dB G = 16 104 dB G = 32 110 dB G = 64 110 dB G = 128 110 dB

Noise

Input Voltage Noise, eni f = 1 kHz 40 nV/√Hz f = 1 kHz, TA = −55°C 35 nV/√Hz f = 1 kHz, TA = 125°C 48 nV/√Hz f = 0.1 Hz to 10 Hz 0.8 μV p-p Output Voltage Noise, eno f = 1 kHz 72 nV/√Hz f = 1 kHz, TA = −55°C 62 nV/√Hz f = 1 kHz, TA = 125°C 83 nV/√Hz f = 0.1 Hz to 10 Hz 1.4 μV p-p Current Noise f = 10 Hz 20 fA/√Hz

Other Input Characteristics

Common-Mode Input Impedance 10||5 GΩ||pF Power Supply Rejection Ratio 100 115 dB Input Operating Voltage Range 0.05 2.95 V

Reference Input

Input Impedance Voltage Range

= 1.5 V, TA = 25°C, G = 1, RL = 10 kΩ, unless otherwise noted.

REF

+ V

/G

OSO

Input Offset, V

Output Offset, V

OSI

4 15 μV

OSI

15 30 μV

OSO

= −55°C to +125°C 5 nA

A

= −55°C to +125°C 0.5 nA

A

G = 1 0.05 % G = 2 to 128 0.8 %

G = 1 to 32 3 10 ppm/°C G = 64 4 20 ppm/°C G = 128 10 30 ppm/°C

e

n

V

IN+

= √(e

, V

IN−

2

+ (eno/G)2)

ni

= 2.5 V, TA = 25°C

28 kΩ||pF

−0.2 +3.2 V

Rev. 0 | Page 5 of 20

AD8231-EP

Parameter Conditions Min Typ Max Unit

Dynamic Performance

Bandwidth

G = 1 2.7 MHz

G = 2 2.5 MHz Gain Bandwidth Product

G = 4 to 128 7 MHz Slew Rate 1.1 V/μs

Output Characteristics

Output Voltage High RL = 100 kΩ to ground 2.9 2.94 V R Output Voltage Low RL = 100 kΩ to 3 V 60 100 mV R Short-Circuit Current 40 mA

Digital Interface

Input Voltage Low TA = −55°C to +125°C 0.7 V Input Voltage High TA = −55°C to +125°C 2.3 V Setup Time to CS High Hold Time after CS High

OPERATIONAL AMPLIFIERS

Input Characteristics

Offset Voltage, VOS 5 15 μV Temperature Drift TA = −55°C to +125°C 0.01 0.06 μV/°C Input Bias Current 250 500 pA T Input Offset Current 20 100 pA T Input Voltage Range 0.05 2.95 V Open-Loop Gain 100 120 V/mV Common-Mode Rejection Ratio 100 120 dB Power Supply Rejection Ratio 100 110 dB Voltage Noise Density 27 nV/√Hz Voltage Noise f = 0.1 Hz to 10 Hz 0.6 μV p-p

Dynamic Performance

Gain Bandwidth Product 1 MHz Slew Rate 0.5 V/μs

Output Characteristics

Output Voltage High RL = 100 kΩ to ground 2.9 2.96 V R Output Voltage Low RL = 100 kΩ to 3 V 60 100 mV R Short-Circuit Current 40 mA

BOTH AMPLIFIERS

Power Supply

Quiescent Current 3.5 4.5 mA Quiescent Current (Shutdown) 0.01 1 μA

= 10 kΩ to ground 2.8 2.88 V

L

= 10 kΩ to 3 V 80 200 mV

L

T

= −55°C to +125°C 60 ns

A

T

= −55°C to +125°C 20 ns

A

= −55°C to +125°C 5 nA

A

= −55°C to +125°C 0.5 nA

A

= 10 kΩ to ground 2.8 2.82 V

L

= 10 kΩ to 3 V 80 200 mV

L

Rev. 0 | Page 6 of 20

ANALOG DEVICES AD8231-EP Service Manual

FEATURES

ENHANCED PRODUCT FEATURES

FUNCTIONAL BLOCK DIAGRAM

GENERAL DESCRIPTION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS