ANALOG DEVICES AD8221 Service Manual

+

Precision Instrumentation Amplifier

FEATURES

Easy to use Available in space-saving MSOP Gain set with 1 external resistor (gain range 1 to 1000) Wide power supply range: ±2.3 V to ±18 V Temperature range for specified performance:

−40°C to +85°C Operational up to 125°C Excellent AC specifications

80 dB minimum CMRR to 10 kHz ( G = 1) 825 kHz, –3 dB bandwidth (G = 1) 2 V/μs slew rate

Low noise

8 nV/√Hz, @ 1 kHz, maximum input voltage noise

0.25 μV p-p input noise (0.1 Hz to 10 Hz) High accuracy dc performance (AD8221BR)

90 dB minimum CMRR (G = 1) 25 μV maximum input offset voltage

0.3 μV/°C maximum input offset drift

0.4 nA maximum input bias current

APPLICATIONS

Weigh scales Industrial process controls Bridge amplifiers Precision data acquisition systems Medical instrumentation Strain gages Transducer interfaces

GENERAL DESCRIPTION

The AD8221 is a gain programmable, high performance instrumentation amplifier that delivers the industry’s highest CMRR over frequency in its class. The CMRR of instrumentation amplifiers on the market today falls off at 200 Hz. In contrast, the AD8221 maintains a minimum CMRR of 80 dB to 10 kHz for all grades at G = 1. High CMRR over frequency allows the AD8221 to reject wideband interference and line harmonics, greatly simplifying filter requirements. Possible applications include precision data acquisition, biomedical analysis, and aerospace instrumentation.

1

AD8221

CONNECTION DIAGRAM

1

–IN

2

R

G

3

R

G

4

IN

AD8221

TOP VIEW

Figure 1.

120

110

100

90

80

CMRR (dB)

70

60

50

40

10010 1k 10k 100k

FREQUENCY (Hz)

Figure 2. Typical CMRR vs. Frequency for G = 1

Low voltage offset, low offset drift, low gain drift, high gain accuracy, and high CMRR make this part an excellent choice in applications that demand the best dc performance possible, such as bridge signal conditioning.

Programmable gain affords the user design flexibility. A single resistor sets the gain from 1 to 1000. The AD8221 operates on both single and dual supplies and is well suited for applications where ±10 V input voltages are encountered.

The AD8221 is available in a low cost 8-lead SOIC and 8-lead MSOP, both of which offer the industry’s best performance. The MSOP requires half the board space of the SOIC, making it ideal for multichannel or space-constrained applications.

Performance is specified over the entire industrial temperature range of −40°C to +85°C for all grades. Furthermore, the AD8221 is operational from −40°C to +125°C

1

See Typical Performance Characteristics for expected operation from

85°C to 125°C.

8

+V

S

7

V

OUT

6

REF

5

–V

S

AD8221

COMPET ITOR 1

COMPET ITOR 2

1

.

03149-001

03149-002

Rev. B

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.

AD8221

REVISION HISTORY

9/07—Rev. A to Rev. B

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

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

Changes to Table 2 Layout............................................................... 5

Changes to Figure 15...................................................................... 11

Changes to Figures 32.................................................................... 13

Changes to Figure 33, Figure 34, and Figure 35......................... 14

Updated Outline Dimensions....................................................... 21

Changes to Ordering Guide.......................................................... 22

11/03—Rev. 0 to Rev. A

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

Changes to Specifications Section.................................................. 4

Changes to Theory of Operation Section.................................... 13

Changes to Gain Selection Section............................................... 14

10/03—Revision 0: Initial Version

Layout ..........................................................................................17

Reference Terminal.................................................................... 18

Power Supply Regulation and Bypassing ................................ 18

Input Bias Current Return Path ............................................... 18

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

RF Interference........................................................................... 19

Precision Strain Gage................................................................. 19

Conditioning ±10 V Signals for a +5 V Differential Input

ADC ............................................................................................. 19

AC-Coupled Instrumentation Amplifier................................ 20

Outline Dimensions .......................................................................21

Ordering Guide .......................................................................... 22

Rev. B | Page 2 of 24

AD8221

SPECIFICATIONS

VS = ±15 V, V

Table 1.

AR Grade BR Grade Parameter Conditions Min Typ Max Min Typ Max Unit

COMMON-MODE REJECTION RATIO

CMRR DC to 60 Hz with 1 kΩ Source Imbalance

G = 1 80 90 dB G = 10 100 110 dB G = 100 120 130 dB G = 1000 130 140 dB

CMRR at 10 kHz VCM = −10 V to +10 V

G = 1 80 80 dB G = 10 90 100 dB G = 100 100 110 dB G = 1000 100 110 dB

NOISE

Voltage Noise, 1 kHz

Input Voltage Noise, e Output Voltage Noise, e

RTI f = 0.1 Hz to 10 Hz

G = 1 2 2 μV p-p G = 10 0.5 0.5 μV p-p G = 100 to 1000 0.25 0.25 μV p-p

Current Noise f = 1 kHz 40 40 fA/√Hz

f = 0.1 Hz to 10 Hz 6 6 pA p-p

VOLTAGE OFFSET

Input Offset, V

Over Temperature T = −40°C to +85°C 86 45 μV Average TC 0.4 0.3 μV/°C

Output Offset, V

Over Temperature T = −40°C to +85°C 0.66 0.45 mV Average TC 6 5 μV/°C

Offset RTI vs. Supply (PSR) VS = ±2.3 V to ±18 V

G = 1 90 110 94 110 dB G = 10 110 120 114 130 dB G = 100 124 130 130 140 dB G = 1000 130 140 140 150 dB

INPUT CURRENT

Input Bias Current 0.5 1.5 0.2 0.4 nA

Over Temperature T = −40°C to +85°C 2.0 1 nA Average TC 1 1 pA/°C

Input Offset Current 0.2 0.6 0.1 0.4 nA

Over Temperature T = −40°C to +85°C 0.8 0.6 nA Average TC 1 1 pA/°C

REFERENCE INPUT

R

IN

I

IN

Voltage Range –V Gain to Output 1 ± 0.0001 1 ± 0.0001 V/V

= 0 V, TA = 25°C, G = 1, RL = 2 kΩ, unless otherwise noted.

REF

= −10 V to +10 V

V

CM

RTI noise =

2

√

e

+ (eNO/G)

NI

V

NI

NO

1

OSI

OSO

, V

IN+

IN−

75 75 nV/√Hz

VS = ±5 V to ±15 V 60 25 μV

VS = ±5 V to ±15 V 300 200 μV

2

, V

= 0 8 8 nV/√Hz

REF

20 20 kΩ V

, V

IN+

= 0 50 60 50 60 μA

IN−

REF

S

+V

S

–V

S

+V

S

V

Rev. B | Page 3 of 24

AD8221

AR Grade BR Grade Parameter Conditions Min Typ Max Min Typ Max Unit

POWER SUPPLY

Operating Range VS = ±2.3 V to ±18 V ±2.3 ±18 ±2.3 ±18 V

Quiescent Current 0.9 1 0.9 1 mA

Over Temperature T = −40°C to +85°C 1 1.2 1 1.2 mA

DYNAMIC RESPONSE

Small Signal −3 dB Bandwidth

G = 1 825 825 kHz G = 10 562 562 kHz G = 100 100 100 kHz G = 1000 14.7 14.7 kHz

Settling Time 0.01% 10 V step

G = 1 to 100 10 10 μs G = 1000 80 80 μs

Settling Time 0.001% 10 V step

G = 1 to 100 13 13 μs G = 1000 110 110 μs

Slew Rate G = 1 1.5 2 1.5 2 V/μs G = 5 to 100 2 2.5 2 2.5 V/μs GAIN G = 1 + (49.4 kΩ/RG)

Gain Range 1 1000 1 1000 V/V

Gain Error V

G = 1 0.03 0.02 % G = 10 0.3 0.15 % G = 100 0.3 0.15 % G = 1000 0.3 0.15 %

Gain Nonlinearity V

G = 1 to 10 RL = 10 kΩ 3 10 3 10 ppm G = 100 RL = 10 kΩ 5 15 5 15 ppm G = 1000 RL = 10 kΩ 10 40 10 40 ppm G = 1 to 100 RL = 2 kΩ 10 95 10 95 ppm

Gain vs. Temperature

G = 1 3 10 2 5 ppm/°C

2

G > 1

INPUT

Input Impedance

Differential 100||2 100||2 GΩ||pF Common Mode 100||2 100||2 GΩ||pF

Input Operating Voltage Range

3

Over Temperature T = −40°C to +85°C –VS + 2.0 +VS − 1.2 –VS + 2.0 +VS − 1.2 V

Input Operating Voltage Range VS = ±5 V to ±18 V –VS + 1.9 +VS − 1.2 –VS + 1.9 +VS − 1.2 V

Over Temperature T =−40°C to +85°C –VS + 2.0 +VS − 1.2 –VS + 2.0 +VS − 1.2 V

OUTPUT RL = 10 kΩ

Output Swing VS = ±2.3 V to ±5 V –VS + 1.1 +VS − 1.2 –VS + 1.1 +VS − 1.2 V

Over Temperature T = −40°C to +85°C –VS + 1.4 +Vs − 1.3 –VS + 1.4 +VS − 1.3 V

Output Swing VS = ±5 V to ±18 V –VS + 1.2 +VS − 1.4 –VS + 1.2 +VS − 1.4 V

Over Temperature T = –40°C to +85°C –VS + 1.6 +VS − 1.5 –VS + 1.6 +VS − 1.5 V

Short-Circuit Current 18 18 mA

± 10 V

OUT

= −10 V to +10 V

OUT

–50 –50 ppm/°C

VS = ±2.3 V to ±5 V –VS + 1.9 +VS − 1.1 –VS + 1.9 +VS − 1.1 V

Rev. B | Page 4 of 24

AD8221

AR Grade BR Grade Parameter Conditions Min Typ Max Min Typ Max Unit

TEMPERATURE RANGE

Specified Performance –40 +85 –40 +85 °C Operating Range

1

Total RTI VOS = (V

2

Does not include the effects of external resistor RG.

3

One input grounded. G = 1.

4

See Typical Performance Characteristics for expected operation between 85°C to 125°C.

Table 2.

Parameter Conditions

COMMON-MODE REJECTION RATIO (CMRR)

CMRR DC to 60 Hz with 1 kΩ Source Imbalance VCM = −10 V to +10 V

G = 1 80 dB G = 10 100 dB G = 100 120 dB G = 1000 130 dB

CMRR at 10 kHz VCM = –10 V to +10 V

G = 1 80 dB G = 10 90 dB G = 100 100 dB G = 1000 100 dB

NOISE

Voltage Noise, 1 kHz

Input Voltage Noise, e Output Voltage Noise, e

RTI f = 0.1 Hz to 10 Hz

G = 1 2 μV p-p G = 10 0.5 μV p-p G = 100 to 1000 0.25 μV p-p

Current Noise f = 1 kHz 40 fA/√Hz

f = 0.1 Hz to 10 Hz 6 pA p-p

VOLTAGE OFFSET

Input Offset, V

Over Temperature T = −40°C to +85°C 135 μV Average TC 0.9 μV/°C

Output Offset, V

Over Temperature T = −40°C to +85°C 1.00 mV Average TC 9 μV/°C

Offset RTI vs. Supply (PSR) VS = ±2.3 V to ±18 V

G = 1 90 100 dB G = 10 100 120 dB G = 100 120 140 dB G = 1000 120 140 dB

INPUT CURRENT

Input Bias Current 0.5 2 nA

Over Temperature T = −40°C to +85°C 3 nA Average TC 3 pA/°C

Input Offset Current 0.3 1 nA

Over Temperature T = −40°C to +85°C 1.5 nA Average TC 3 pA/°C

OSI

) + (V

1

OSI

OSO

4

/G).

OSO

–40 +125 –40 +125 °C

ARM Grade

Min Typ Max

RTI noise = √

V

NI

NO

, V

IN+

IN−

75 nV/√Hz

2

e

+ (eNO/G)

NI

, V

= 0 8 nV/√Hz

REF

2

Unit

VS = ±5 V to ±15 V 70 μV

VS = ±5 V to ±15 V 600 μV

Rev. B | Page 5 of 24

AD8221

ARM Grade

Parameter Conditions

Min Typ Max

REFERENCE INPUT

R

IN

I

IN

Voltage Range −V

20 kΩ V

, V

IN+

= 0 50 60 μA

IN−

REF

S

+V

S

Gain to Output 1 ± 0.0001 V/V POWER SUPPLY

Operating Range VS = ±2.3 V to ±18 V ±2.3 ±18 V

Quiescent Current 0.9 1 mA

Over Temperature T = −40°C to +85°C 1 1.2 mA

DYNAMIC RESPONSE

Small Signal –3 dB Bandwidth

G = 1 825 kHz G = 10 562 kHz G = 100 100 kHz G = 1000 14.7 kHz

Settling Time 0.01% 10 V step

G = 1 to 100 10 μs G = 1000 80 μs

Settling Time 0.001% 10 V step

G = 1 to 100 13 μs G = 1000 110 μs

Slew Rate G = 1 1.5 2 V/μs G = 5 to 100 2 2.5 V/μs GAIN G = 1 + (49.4 kΩ/RG)

Gain Range 1 1000 V/V

Gain Error V

± 10 V

OUT

G = 1 0.1 % G = 10 0.3 % G = 100 0.3 % G = 1000 0.3 %

Gain Nonlinearity V

= −10 V to +10 V

OUT

G = 1 to 10 RL = 10 kΩ 5 15 ppm G = 100 RL = 10 kΩ 7 20 ppm G = 1000 RL = 10 kΩ 10 50 ppm G = 1 to 100 RL = 2 kΩ 15 100 ppm

Gain vs. Temperature

G = 1 3 10 ppm/°C

2

G > 1

–50 ppm/°C

INPUT

Input Impedance

Differential 100||2 GΩ/pF Common Mode 100||2 GΩ/pF

Input Operating Voltage Range

3

VS = ±2.3 V to ±5 V –VS + 1.9 +VS − 1.1 V

Over Temperature T = −40°C to +85°C –VS + 2.0 +VS − 1.2 V

Input Operating Voltage Range VS = ±5 V to ±18 V –VS + 1.9 +VS − 1.2 V

Over Temperature T = −40°C to +85°C –VS + 2.0 +VS − 1.2 V

OUTPUT RL = 10 kΩ

Output Swing VS = ±2.3 V to ±5 V –VS + 1.1 +VS − 1.2 V

Over Temperature T = −40°C to +85°C –VS + 1.4 +VS − 1.3 V

Output Swing VS = ±5 V to ±18 V –VS + 1.2 +VS − 1.4 V

Over Temperature T = −40°C to +85°C –VS + 1.6 +VS − 1.5 V

Short-Circuit Current 18 mA

Unit

V

Rev. B | Page 6 of 24

AD8221

ARM Grade

Parameter Conditions

Min Typ Max

TEMPERATURE RANGE

Specified Performance −40 +85 °C

OSI

) + (V

4

/G).

OSO

−40 +125 °C

Operating Range

1

Total RTI VOS = (V

2

Does not include the effects of external resistor RG.

3

One input grounded. G = 1.

4

See Typical Performance Characteristics for expected operation between 85°C to 125°C.

Unit

Rev. B | Page 7 of 24

AD8221

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage ±18 V Internal Power Dissipation 200 mW Output Short-Circuit Current Indefinite Input Voltage (Common-Mode) ±V Differential Input Voltage ±V Storage Temperature Range −65°C to +150°C Operating Temperature Range

1

Temperature range for specified performance is –40°C to +85°C. See Typical

Performance Characteristics for expected operation from 85°C to 125°C.

1

S

−40°C to +125°C

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

Specification for a device in free air.

Table 4.

Package θ

8-Lead SOIC, 4-Layer JEDEC Board 121 °C/W 8-Lead MSOP, 4-Layer JEDEC Board 135 °C/W

Unit

JA

ESD CAUTION

Rev. B | Page 8 of 24

ANALOG DEVICES AD8221 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

CONNECTION DIAGRAM

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

THERMAL CHARACTERISTICS

ESD CAUTION