ANALOG DEVICES AD8572 Service Manual

Zero-Drift, Single-Supply, Rail-to-Rail

–

O

www.BDTIC.com/ADI

Input/Output Operational Amplifiers

FEATURES

Low offset voltage: 1 μV
Input offset drift: 0.005 μV/°C
Rail-to-rail input and output swing
5 V/2.7 V single-supply operation
High gain: 145 dB typical
CMRR: 140 dB typical
PSRR: 130 dB typical
Ultralow input bias current: 10 pA typical
Low supply current: 750 μA per op amp
Overload recovery time: 50 μs
No external capacitors required

APPLICATIONS

Temperature sensors
Pressure sensors
Precision current sensing
Strain gage amplifiers
Medical instrumentation
Thermocouple amplifiers

GENERAL DESCRIPTION

This family of amplifiers has ultralow offset, drift, and bias
current. The AD8571, AD8572, and AD8574 are single, dual,
and quad amplifiers, respectively, featuring rail-to-rail input
and output swings. All are guaranteed to operate from 2.7 V to
5 V single supply.

The AD857x family provides benefits previously found only in
expensive auto-zeroing or chopper-stabilized amplifiers. Using
Analog Devices, Inc., topology, these zero-drift amplifiers
combine low cost with high accuracy. (No external capacitors
are required.) Using a patented spread-spectrum, auto-zero
technique, the AD857x family eliminates the intermodulation
effects from interaction of the chopping function with the
signal frequency in ac applications.

With an offset voltage of only 1 µV and drift of 0.005 µV/°C, the
AD857x family is perfectly suited for applications where error
sources cannot be tolerated. Position and pressure sensors,
medical equipment, and strain gage amplifiers benefit greatly
from nearly zero drift over their operating temperature range.
Many more systems require the rail-to-rail input and output
swings provided by the AD857x family.

AD8571/AD8572/AD8574

PIN CONFIGURATIONS

1

NC

AD8571

2

–IN A

+IN A

TOP VIEW

3

(Not to Scale)

V–

4

NC = NO CONNECT

Figure 1. 8-Lead MSOP (RM Suffix)

1

NC

2

IN A

+IN A

AD8571

3

TOP VIEW

(Not to Scale)

V–

4

NC = NO CONNECT

Figure 2. 8-Lead SOIC (R Suffix)

1

OUT A V+

–IN A

+IN A

V–

AD8572

2

TOP VIEW

3

(Not to Scale)

4

Figure 3. 8-Lead TSSOP (RU Suffix)

1

OUT A V+

–IN A

+IN A

V–

AD8572

2

TOP VIEW

3

(Not to Scale)

4

Figure 4. 8-Lead SOIC (R Suffix)

OUT A

1

–IN A

2

+IN A

3

AD8574

V+

4

TOP VIEW

+IN B

–IN B

OUT B

(Not to Scale)

5

6

7

Figure 5. 14-Lead TSSOP (RU Suffix)

OUT A

1

–IN A

2

+IN A

3

AD8574

V+

4

TOP VIEW

UT B

(Not to S cale)

5

6

7

+IN B

–IN B

Figure 6. 14-Lead SOIC (R Suffix)

The AD857x family is specified for the extended industrial/
automotive temperature range (−40°C to +125°C). The AD8571
single amplifier is available in 8-lead MSOP and narrow SOIC
packages. The AD8572 dual amplifier is available in 8-lead narrow
SOIC and surface-mount TSSOP packages. The AD8574 quad
amplifier is available in 14-lead narrow SOIC and TSSOP packages.

8

7

6

5

8

7

6

5

8

7

6

5

8

7

6

5

14

13

12

11

10

9

8

14

13

12

11

10

9

8

NC

V+

OUT A

NC

NC

V+

OUT A

NC

OUT B

–IN B

+IN B

OUT B

–IN B

+IN B

OUT D

–IN D

+IN D

V–

+IN C

–IN C

OUT C

OUT D

–IN D

+IN D

V–

+IN C

–IN C

OUT C

1104-001

01104-004

01104-002

01104-005

01104-003

1104-006

Rev. D

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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©1999–2008 Analog Devices, Inc. All rights reserved.

AD8571/AD8572/AD8574

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TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1

General Description ......................................................................... 1

Pin Configurations ........................................................................... 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

5 V Electrical Characteristics ...................................................... 3

2.7 V Electrical Characteristics ................................................... 4

Absolute Maximum Ratings ............................................................ 5

Thermal Characteristics .............................................................. 5

ESD Caution .................................................................................. 5

Typical Performance Characteristics ............................................. 6

Functional Description .................................................................. 14

Amplifier Architecture .............................................................. 14

Basic Auto-Zero Amplifier Theory .......................................... 14

Auto-Zero Phase ......................................................................... 15

Amplification Phase ................................................................... 15

High Gain, CMRR, and PSRR .................................................. 16

Maximizing Performance Through Proper Layout ............... 16

1/f Noise Characteristics ........................................................... 17

Random Auto-Zero Correction Eliminates Intermodulation

Distortion .................................................................................... 17

Broadband and External Resistor Noise Considerations .......... 18

Output Overdrive Recovery ...................................................... 18

Input Overvoltage Protection ................................................... 18

Output Phase Reversal ............................................................... 18

Capacitive Load Drive ............................................................... 19

Power-Up Behavior .................................................................... 19

Applications Information .............................................................. 20

5 V Precision Strain Gage Circuit ............................................ 20

3 V Instrumentation Amplifier ................................................ 20

High Accuracy Thermocouple Amplifier ............................... 21

Precision Current Meter ............................................................ 21

Precision Voltage Comparator .................................................. 21

Outline Dimensions ....................................................................... 22

Ordering Guide .......................................................................... 23

REVISION HISTORY

6/08—Rev. C to Rev. D

Changes to Figure 19 and Figure 20 ............................................... 8

Changes to Figure 44 ...................................................................... 12

Changes to Figure 38 ...................................................................... 13

Moved Figure 50 and Figure 51 .................................................... 14

Changes to Figure 66, Precision Current Meter Section, Layout,

Figure 67, Equation 24, and Figure 68 ......................................... 21

5/07—Rev. B to Rev. C

Changes to Features .......................................................................... 1

Changes to Table 1 ............................................................................ 3

Changes to Table 2 ............................................................................ 4

Changes to Basic Auto-Zero Amplifier Theory Section ........... 14

Changes to Figure 50 ...................................................................... 15

Changes to Figure 55 ...................................................................... 16

Changes to Figure 66 ...................................................................... 21

Updated Outline Dimensions ....................................................... 22

9/06—Rev. A to Rev. B

Updated Format .................................................................. Universal

Changes to Table 1 ............................................................................. 3

Changes to Table 2 ............................................................................. 4

Changes to Figure 50 ...................................................................... 14

Changes to Figure 51 ...................................................................... 15

Changes to Figure 66 ...................................................................... 21

Deleted Figure 69 and SPICE Macro-Model Section ................ 17

Deleted SPICE Macro-Model for the AD857x Section ............. 18

Updated Outline Dimensions ....................................................... 22

Changes to Ordering Guide .......................................................... 23

7/03—Rev. 0 to Rev. A

Renumbered Figures .......................................................... Universal

Changes to Ordering Guide ............................................................. 4

Change to Figure 15. ...................................................................... 16

Updated Outline Dimensions ....................................................... 19

10/99—Revision 0: Initial Version

Rev. D | Page 2 of 24

AD8571/AD8572/AD8574

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SPECIFICATIONS

5 V ELECTRICAL CHARACTERISTICS

VS = 5 V, VCM = 2.5 V, VO = 2.5 V, TA = 25°C, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 1 5 V

−40°C ≤ TA ≤ +125°C 10 V
Input Bias Current IB 10 50 pA

AD8571/AD8574 −40°C ≤ TA ≤ +125°C 1.0 1.5 nA
AD8572 −40°C ≤ TA ≤ +85°C 160 300 pA

−40°C ≤ TA ≤ +125°C 2.5 4 nA
Input Offset Current IOS 20 70 pA

AD8571/AD8574 −40°C ≤ TA ≤ +125°C 150 200 pA
AD8572 −40°C ≤ TA ≤ +85°C 30 150 pA

−40°C ≤ TA ≤ +125°C 150 400 pA
Input Voltage Range 0 5 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 5 V 120 140 dB

−40°C ≤ TA ≤ +125°C 115 130 dB
Large Signal Voltage Gain

−40°C ≤ TA ≤ +125°C 120 135 dB
Offset Voltage Drift VOS/T −40°C ≤ TA ≤ +125°C 0.005 0.04 V/°C

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

R

R

R

Output Voltage Low VOL R

R

R

Short-Circuit Limit ISC ±25 ±50 mA

−40°C to +125°C ±40 mA
Output Current IO ±30 mA

−40°C to +125°C ±15 mA

POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 120 130 dB

−40°C ≤ TA ≤ +125°C 115 130 dB
Supply Current per Amplifier ISY V

−40°C ≤ TA ≤ +125°C 1000 1075 A

DYNAMIC PERFORMANCE

Slew Rate SR RL = 10 kΩ 0.4 V/s
Overload Recovery Time 0.05 0.3 ms
Gain Bandwidth Product GBP 1.5 MHz

NOISE PERFORMANCE

Voltage Noise en p-p 0 Hz to 10 Hz 1.3 V p-p
0 Hz to 1 Hz 0.41 V p-p
Voltage Noise Density en f = 1 kHz 51 nV/√Hz
Current Noise Density in f = 10 Hz 2 fA/√Hz

1

Gain testing is dependent upon test bandwidth.

1

A

R

VO

= 10 kΩ, VO = 0.3 V to 4.7 V 125 145 dB

L

= 100 kΩ to GND 4.99 4.998 V

L

= 100 kΩ to GND @ −40°C to +125°C 4.99 4.997 V

L

= 10 kΩ to GND 4.95 4.98 V

L

= 10 kΩ to GND @ −40°C to +125°C 4.95 4.975 V

L

= 100 kΩ to V+ 1 10 mV

L

= 100 kΩ to V+ @ −40°C to +125°C 2 10 mV

R

L

= 10 kΩ to V+ 10 30 mV

L

= 10 kΩ to V+ @ −40°C to +125°C 15 30 mV

L

= 0 V 850 975 A

O

Rev. D | Page 3 of 24

AD8571/AD8572/AD8574

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2.7 V ELECTRICAL CHARACTERISTICS

VS = 2.7 V, VCM = 1.35 V, VO = 1.35 V, TA = 25°C, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 1 5 V

−40°C ≤ TA ≤ +125°C 10 V

Input Bias Current IB 10 50 pA

AD8571/AD8574 −40°C ≤ TA ≤ +125°C 1.0 1.5 nA
AD8572 −40°C ≤ TA ≤ +85°C 160 300 pA

−40°C ≤ TA ≤ +125°C 2.5 4 nA

Input Offset Current IOS 10 50 pA

AD8571/AD8574 −40°C ≤ TA ≤ +125°C 150 200 pA
AD8572 −40°C ≤ TA ≤ +85°C 30 150 pA

−40°C ≤ TA ≤ +125°C 150 400 pA

Input Voltage Range 0 2.7 V

Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.7 V 115 130 dB

−40°C ≤ TA ≤ +125°C 110 130 dB

Large Signal Voltage Gain

−40°C ≤ TA ≤ +125°C 105 130 dB

Offset Voltage Drift VOS/T −40°C ≤ TA ≤ +125°C 0.005 0.04 µV/°C
OUTPUT CHARACTERISTICS

Output Voltage High VOH R

R

R

R

Output Voltage Low VOL R

R

R

R

Short-Circuit Limit ISC ±10 ±15 mA

−40°C to +125°C ±10 mA

Output Current IO ±10 mA

−40°C to +125°C ±5 mA

POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 120 130 dB

−40°C ≤ TA ≤ +125°C 115 130 dB

Supply Current per Amplifier ISY V

−40°C ≤ TA ≤ +125°C 950 1000 A

DYNAMIC PERFORMANCE

Slew Rate SR RL = 10 kΩ 0.5 V/s

Overload Recovery Time 0.05 ms

Gain Bandwidth Product GBP 1 MHz
NOISE PERFORMANCE

Voltage Noise en p-p 0 Hz to 10 Hz 2.0 V p-p

Voltage Noise Density en f = 1 kHz 94 nV/√Hz

Current Noise Density in f = 10 Hz 2 fA/√Hz

1

Gain testing is dependent upon test bandwidth.

1

A

R

VO

= 10 kΩ, VO = 0.3 V to 2.4 V 110 140 dB

L

= 100 kΩ to GND 2.685 2.697 V

L

= 100 kΩ to GND @ −40°C to +125°C 2.685 2.696 V

L

= 10 kΩ to GND 2.67 2.68 V

L

= 10 kΩ to GND @ −40°C to +125°C 2.67 2.675 V

L

= 100 kΩ to V+ 1 10 mV

L

= 100 kΩ to V+ @ −40°C to +125°C 2 10 mV

L

= 10 kΩ to V+ 10 20 mV

L

= 10 kΩ to V+ @ −40°C to +125°C 15 20 mV

L

= 0 V 750 900 A

O

Rev. D | Page 4 of 24

AD8571/AD8572/AD8574

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ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 6 V
Input Voltage GND to VS + 0.3 V
Differential Input Voltage
ESD (Human Body Model) 2000 V
Output Short-Circuit Duration to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C

1

Differential input voltage is limited to ±5.0 V or the supply voltage,

whichever is less.

1

±5.0 V

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational section of
this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.

THERMAL CHARACTERISTICS

θJA is specified for the worst-case conditions, that is, θJA is
specified for a device soldered in a circuit board for SOIC and
TSSOP packages.

Table 4. Thermal Resistance

Package Type θJA θ

8-Lead SOIC (R) 158 43 °C/W
8-Lead MSOP (RM) 190 44 °C/W
8-Lead TSSOP (RU) 240 43 °C/W
14-Lead SOIC (R) 120 36 °C/W
14-Lead TSSOP (RU) 180 36 °C/W

Unit

JC

ESD CAUTION

Rev. D | Page 5 of 24

AD8571/AD8572/AD8574

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TYPICAL PERFORMANCE CHARACTERISTICS

NUMBER OF AMPL IFIERS

180

160

140

120

100

80

60

40

20

0

–1.5–2.5 –0.5 0.5 1.5 2.5

OFFSET VO LTAGE (µV)

Figure 10. Input Offset Voltage Distribution

VS = 5V
V

= 2.5V

CM

T

= 25°C

A

1104-010

180

160

140

120

100

80

60

NUMBER OF AMPLIFIERS

40

20

0

–1.5–2.5 –0.5 0.5 1.5 2.5

OFFSET VOLTAGE (µV)

VS = 2.7V
V

= 1.35V

CM

T

= 25°C

A

01104-007

Figure 7. Input Offset Voltage Distribution

50

= 5V

V

S

T

= –40°C, +25° C, +85°C

40

A

30

20

10

0

–10

INPUT BIAS CURRENT (pA)

–20

–30

012 435

INPUT COMMO N-MODE VOL TAGE (V)

+85°C

+25°C

–40°C

01104-008

Figure 8. Input Bias Current vs. Input Common-Mode Voltage

1500

V

= 5V

S

T

= 125°C

A

1000

500

0

–500

–1000

INPUT BIAS CURRENT (pA)

–1500

12

10

8

6

4

NUMBER OF AMPLIFIERS

2

0

01234 65

INPUT OFFSET DRIFT (nV/°C)

Figure 11. Input Offset Voltage Drift Distribution

10k

VS = 5V
T

= 25°C

A

1k

100

10

OUTPUT VOLTAGE (mV)

1

SOURCE

VS = 5V
V

= 2.5V

CM

T

= –40°C TO +125°C

A

SINK

1104-011

–2000

012345

COMMON-MODE VOLTAGE (V)

Figure 9. Input Bias Current vs. Common-Mode Voltage

01104-009

0.1

0.0001 0.001 0.01 0. 1 100101

LOAD CURRENT (mA)

Figure 12. Output Voltage to Supply Rail vs. Load Current

Rev. D | Page 6 of 24

01104-012

AD8571/AD8572/AD8574

www.BDTIC.com/ADI

10k

= 2.7V

V

S

T

= 25°C

A

1k

800

700

600

T

A

= 25°C

100

10

OUTPUT VOL TAGE (mV)

1

0.1

0.0001 0.001 0.01 0. 1 1 10 100

SOURCE

LOAD CURRENT (mA)

SINK

Figure 13. Output Voltage to Supply Rail vs. Load Current

1000

VCM = 2.5V
V

= 5V

S

750

500

250

INPUT BIAS CURRENT (pA)

0

–75 –50 –25 0 25 50 75 100 125 150

TEMPERATURE ( °C)

Figure 14. Input Bias Current vs. Temperature

1.0

0.8

0.6

0.4

SUPPLY CURRENT (mA)

0.2

0

–75 –25–50 25 750 50 100 150125

TEMPERATURE (° C)

5V

2.7V

Figure 15. Supply Current vs. Temperature

500

400

300

200

100

SUPPLY CURRENT PER AMPLIFIER (µA)

0

01 2 34 5 6

01104-013

SUPPLY VOLTAGE (V)

01104-016

Figure 16. Supply Current per Amplifier vs. Supply Voltage

60

VS= 2.7V
C

= 0pF

50

L

R

=

∞

L

40

30

20

10

0

–10

OPEN-LOOP GAIN (dB)

–20

–30

–40

10k 100k 1M 10M 100M

01104-014

FREQUENCY (Hz)

0

45

90

135

180

225

270

PHASE SHIF T (Degrees)

01104-017

Figure 17. Open-Loop Gain and Phase Shift vs. Frequency

60

V

= 5V

S

C

= 0pF

50

L

R

=

∞

L

40

30

20

10

0

–10

OPEN-LOOP GAIN (dB)

–20

–30

–40

10k 100k 1M 10M 100M

01104-015

FREQUENCY (Hz)

0

45

90

135

180

225

270

PHASE SHIFT (Degrees)

01104-018

Figure 18. Open-Loop Gain and Phase Shift vs. Frequency

Rev. D | Page 7 of 24

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60

50

40

AV = 100

30

20

= 10

A

V

10

0

AV = 1

–10

CLOSED-LOOP GAIN (dB)

–20

–30

–40

100 10k1k 1M100k 10M

FREQUENCY (Hz)

Figure 19. Closed-Loop Gain vs. Frequency

V

S

C

L

R

L

= 2.7V

= 20pF
= 2kΩ

01104-019

300

VS= 5V

270

240

210

180

150

120

90

OUTPUT IMPEDANCE (Ω)

60

30

0

100 10 k1k 10M

FREQUENCY (Hz)

AV = 100

AV = 10

AV = 1

Figure 22. Output Impedance vs. Frequency

1M100k

01104-022

60

50

40

AV = 100

30

20

A

= 10

V

10

0

AV = 1

–10

CLOSED-LOOP GAIN (dB)

–20

–30

–40

100 10k1k 1M100k 10M

FREQUENCY (Hz)

Figure 20. Closed-Loop Gain vs. Frequency

300

VS= 2.7V

270

240

210

180

150

120

90

OUTPUT IM PEDANCE (Ω)

60

30

0

100 10k1k 10M

FREQUENCY (Hz)

AV = 100

AV = 10

AV = 1

Figure 21. Output Impedance vs. Frequency

V
C
R

1M100k

= 5V

S

= 20pF

L

= 2kΩ

L

VS = 2.7V
C

= 300pF

L

R

= 2kΩ

L

A

= 1

V

2µs 500mV

01104-020

1104-023

Figure 23. Large Signal Transient Response

VS = 5V
C

= 300pF

L

R

= 2kΩ

L

A

= 1

V

5µs 1V

1104-021

01104-024

Figure 24. Large Signal Transient Response

Rev. D | Page 8 of 24