ANALOG DEVICES AD8220 Service Manual

JFET Input Instrumentation Amplifier with

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Rail-to-Rail Output in MSOP Package

FEATURES

Low input currents

10 pA maximum input bias current (B Grade)

0.6 pA maximum input offset current (B Grade)

High CMRR

100 dB CMRR (minimum), G = 10 (B Grade) 80 dB CMRR (minimum) to 5 kHz, G = 1 (B Grade)

Excellent ac specifications and low power

1.5 MHz bandwidth (G = 1) 14 nV/√Hz input noise (1 kHz) Slew rate: 2 V/μs 750 μA quiescent supply current (maximum)

Versa tile

MSOP package Rail-to-rail output Input voltage range to below negative supply rail 4 kV ESD protection

4.5 V to 36 V single supply ±2.25 V to ±18 V dual supply Gain set with single resistor (G = 1 to 1000)

APPLICATIONS

Medical instrumentation Precision data acquisition Transducer interfaces

GENERAL DESCRIPTION

The AD8220 is the first single-supply, JFET input instrumentation amplifier available in an MSOP package. Designed to meet the needs of high performance, portable instrumentation, the AD8220 has a minimum common-mode rejection ratio (CMRR) of 86 dB at dc and a minimum CMRR of 80 dB at 5 kHz for G = 1. Maximum input bias current is 10 pA and typically remains below 300 pA over the entire industrial temperature range. Despite the JFET inputs, the AD8220 typically has a noise corner of only 10 Hz.

With the proliferation of mixed-signal processing, the number o

f power supplies required in each system has grown. The AD8220 is designed to alleviate this problem. The AD8220 can operate on a ±18 V dual supply, as well as on a single +5 V supply. Its rail-to-rail output stage maximizes dynamic range on the low voltage supplies common in portable applications. Its ability to run on a single 5 V supply eliminates the need to use higher voltage, dual supplies. The AD8220 draws a maximum of 750 μA of quiescent current, making it ideal for battery powered devices.

Rev. A

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.

AD8220

PIN CONFIGURATION

AD8220

1

–IN

2

R

G

3

R

G

4

+IN

TOP VIEW

(Not to Scale)

Figure 1.

10n

1n

100p

10p

1p

INPUT BIAS CURRE NT (A)

0.1p

–25 0 25 50 75 100 125

–50 150

TEMPERATURE (°C)

Figure 2. Input Bias Current and Offset Current vs. Temperature

Gain is set from 1 to 1000 with a single resistor. Increasing the ga

in increases the common-mode rejection. Measurements that need higher CMRR when reading small signals benefit when the AD8220 is set for large gains.

A reference pin allows the user to offset the output voltage. This fe

ature is useful when interfacing with analog-to-digital converters.

The AD8220 is available in an MSOP that takes roughly half the b

oard area of an SOIC. Performance is specified over the industrial

temperature range of −40°C to +85°C.

8

7

6

5

I

BIAS

+V

V

REF

–V

OUT

S

03579-005

I

OS

03579-059

AD8220

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REVISION HISTORY

5/07—Rev. 0 to Rev. A

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

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

Changes to Table 3............................................................................ 8

Changes to Figure 6 and Figure 7................................................. 10

Changes to Figure 23 and Figure 24............................................. 13

Changes to Theory of Operation.................................................. 19

Changes to Layout.......................................................................... 20

Changes to Ordering Guide.......................................................... 26

4/06—Revision 0: Initial Version

Rev. A | Page 2 of 28

AD8220

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SPECIFICATIONS

VS+ = 15 V, VS− = −15 V, V

Table 1.

Parameter Test Conditions Min Typ Max Min Typ Max Unit

COMMON-MODE REJECTION RATIO (CMRR)

CMRR DC to 60 Hz with

1 kΩ Source Imbalance G = 1 78 86 dB G = 10 94 100 dB G = 100 94 100 dB G = 1000 94 100 dB

CMRR at 5 kHz VCM = ±10 V

G = 1 74 80 dB G = 10 84 90 dB G = 100 84 90 dB G = 1000 84 90 dB

NOISE

Voltage Noise, 1 kHz Input Voltage Noise, e Output Voltage Noise, e RTI, 0.1 Hz to 10 Hz

G = 1 5 5 μV p-p G = 1000 0.8 0.8 μV p-p

Current Noise f = 1 kHz 1 1 fA/√Hz

VOLTAGE OFFSET VOS = V

Input Offset, V

Average TC T = −40°C to +85°C 10 5 μV/°C

Output Offset, V

Average TC T = −40°C to +85°C 10 5 μV/°C

Offset RTI vs. Supply (PSR) VS = ±5 V to ±15 V

G = 1 86 86 dB G = 10 96 100 dB G = 100 96 100 dB G = 1000 96 100 dB

INPUT CURRENT

Input Bias Current 25 10 pA

Over Temperature T = −40°C to +85°C 300 300 pA

Input Offset Current 2 0.6 pA

Over Temperature T = −40°C to +85°C 5 5 pA

DYNAMIC RESPONSE

Small Signal Bandwidth, – 3 dB

G = 1 1500 1500 kHz G = 10 800 800 kHz G = 100 120 120 kHz G = 1000 14 14 kHz

OSI

OSO

= 0 V, TA = 25°C, G = 1, RL = 2 kΩ1, unless otherwise noted.

REF

A Grade B Grade

V

= ±10 V

CM

RTI noise =

2

+ (eno/G)2)

√(e

ni

no

VIN+, VIN− = 0 V 14 14 17 nV/√Hz VIN+, VIN− = 0 V 90 90 100 nV/√Hz

+ V

OSI

OSO

250 125 μV

750 500 μV

/G

Rev. A | Page 3 of 28

AD8220

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Parameter Test Conditions Min Typ Max Min Typ Max Unit

Settling Time 0.01% 10 V step

G = 1 5 5 μs G = 10 4.3 4.3 μs G = 100 8.1 8.1 μs G = 1000 58 58 μs

Settling Time 0.001% 10 V step

G = 1 6 6 μs G = 10 4.6 4.6 μs G = 100 9.6 9.6 μs G = 1000 74 74 μs

Slew Rate

G = 1 to 100 2 2 V/μs

GAIN G = 1 + (49.4 kΩ/RG)

Gain Range 1 1000 1 1000 V/V

Gain Error V

G = 1 0.06 0.04 % G = 10 0.3 0.2 % G = 100 0.3 0.2 % G = 1000 0.3 0.2 %

Gain Nonlinearity V

G = 1 RL = 10 kΩ 10 15 10 15 ppm G = 10 RL = 10 kΩ 5 10 5 10 ppm G = 100 RL = 10 kΩ 30 60 30 60 ppm G = 1000 RL = 10 kΩ 400 500 400 500 ppm G = 1 RL = 2 kΩ 10 15 10 15 ppm G = 10 RL = 2 kΩ 10 15 10 15 ppm G = 100 RL = 2 kΩ 50 75 50 75 ppm

Gain vs. Temperature

G = 1 3 10 2 5 ppm/°C G > 10 −50 −50 ppm/°C

INPUT

Impedance (Pin to Ground)

Input Operating Voltage Range

Over Temperature T = −40°C to +85°C −VS − 0.1 +VS − 2.1 −VS − 0.1 +VS − 2.1 V

OUTPUT

Output Swing RL = 2 kΩ −14.3 +14.3 −14.3 +14.3 V

Over Temperature T = −40°C to +85°C −14.3 +14.1 −14.3 +14.1 V

Output Swing RL = 10 kΩ −14.7 +14.7 −14.7 +14.7 V

Over Temperature T = −40°C to +85°C −14.6 +14.6 −14.6 +14.6 V

Short-Circuit Current 15 15 mA REFERENCE INPUT

R

IN

I

IN

Voltage Range −V

Gain to Output

2

3

= ±10 V

OUT

= −10 V to +10 V

OUT

104||5 104||5 GΩ||pF VS = ±2.25 V to ±18 V

for dual supplies

40 40 kΩ VIN+, VIN− = 0 V 70 70 μA

−V

A Grade B Grade

− 0.1 +VS − 2 −VS − 0.1 +VS − 2 V

S

+V 1 ±

0.0001

S

−V

S

+V 1 ±

0.0001

V/V

S

V

Rev. A | Page 4 of 28

AD8220

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Parameter Test Conditions Min Typ Max Min Typ Max Unit

POWER SUPPLY

Operating Range ±2.25 Quiescent Current 750 750 μA

Over Temperature T = −40°C to +85°C 850 850 μA

TEMPERATURE RANGE

For Specified Performance −40 +85 −40 +85 °C Operational

1

When the output sinks more than 4 mA, use a 47 pF capacitor in parallel with the load to prevent ringing. Otherwise, use a larger load, such as 10 kΩ.

2

Differential and common-mode input impedance can be calculated from the pin impedance: Z

3

The AD8220 can operate up to a diode drop below the negative supply but the bias current increases sharply. The input voltage range reflects the maximum

allowable voltage where the input bias current is within the specification.

4

At this supply voltage, ensure that the input common-mode voltage is within the input voltage range specification.

5

The AD8220 is characterized from −40°C to +125°C. See the Typical Performance Characteristics section for expected operation in this temperature range.

5

−40 +125 −40 +125 °C

V

+ = 5 V, VS− = 0 V, V

S

= 2.5 V, TA = 25°C, G = 1, RL = 2 kΩ1, unless otherwise noted.

REF

Table 2.

A Grade B Grade Parameter Test Conditions Min Typ Max Min Typ Max Unit

COMMON-MODE REJECTION RATIO (CMRR)

V

CMRR DC to 60 Hz with

= 0 to 2.5 V

CM

1 kΩ Source Imbalance G = 1 78 86 dB G = 10 94 100 dB G = 100 94 100 dB G = 1000 94 100 dB

CMRR at 5 kHz VCM = 0 to 2.5 V

G = 1 74 80 dB G = 10 84 90 dB G = 100 84 90 dB G = 1000 84 90 dB

NOISE

RTI noise =

2

+ (eno/G)2)

√(e

ni

Voltage Noise, 1 kHz VS = ±2.5 V Input Voltage Noise, e Output Voltage Noise, e

ni

no

VIN+, VIN− = 0 V, V VIN+, VIN− = 0 V, V

= 0 V 14 14 17 nV/√Hz

REF

= 0 V 90 90 100 nV/√Hz

REF

RTI, 0.1 Hz to 10 Hz

G = 1 5 5 μV p-p G = 1000 0.8 0.8 μV p-p

Current Noise f = 1 kHz 1 1 fA/√Hz

VOLTAGE OFFSET VOS = V

+ V

OSI

/G

OSO

Input Offset, VOSI 300 200 μV

Average TC T = −40°C to +85°C 10 5 μV/°C

Output Offset, VOSO 800 600 μV

Average TC T = −40°C to +85°C 10 5 μV/°C

Offset RTI vs. Supply (PSR)

G = 1 86 86 dB G = 10 96 100 dB G = 100 96 100 dB G = 1000 96 100 dB

A Grade B Grade

4

±18 ±2.25

= 2(Z

DIFF

); ZCM = Z

/2.

4

±18 V

Rev. A | Page 5 of 28

AD8220

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A Grade B Grade Parameter Test Conditions Min Typ Max Min Typ Max Unit

INPUT CURRENT

Input Bias Current 25 10 pA

Over Temperature T = −40°C to +85°C 300 300 pA

Input Offset Current 2 0.6 pA

Over Temperature T = −40°C to +85°C 5 5 pA

DYNAMIC RESPONSE

Small Signal Bandwidth, – 3 dB

G = 1 1500 1500 kHz G = 10 G = 100 G = 1000

Settling Time 0.01%

G = 1 3 V step 2.5 2.5 μs G = 10 4 V step 2.5 2.5 μs G = 100 4 V step 7.5 7.5 μs G = 1000 4 V step 30 30 μs

Settling Time 0.001%

G = 1 3 V step 3.5 3.5 μs G = 10 4 V step 3.5 3.5 μs G = 100 4 V step 8.5 8.5 μs G = 1000 4 V step 37 37 μs

Slew Rate

G = 1 to 100

GAIN G = 1 + (49.4 kΩ/RG)

Gain Range

Gain Error

G = 1 0.06 0.04 % G = 10 G = 100 G = 1000

Nonlinearity

G = 1 RL = 10 kΩ 35 50 35 50 ppm G = 10 RL = 10 kΩ 35 50 35 50 ppm G = 100 RL = 10 kΩ 50 75 50 75 ppm G = 1000 RL = 10 kΩ 650 750 650 750 ppm G = 1 G = 10 G = 100

Gain vs. Temperature

G = 1 G > 10

INPUT

Impedance (Pin to Ground)

Input Voltage Range

Over Temperature T = −40°C to +85°C −0.1 +VS − 2.1 −0.1 +VS − 2.1 V

2

3

= 0.3 V to 2.9 V for G = 1,

V

OUT

= 0.3 V to 3.8 V for G > 1

V

OUT

= 0.3 V to 2.9 V for G = 1,

V

OUT

= 0.3 V to 3.8 V for G > 1

V

OUT

R

= 2 kΩ

L

R

= 2 kΩ

L

R

= 2 kΩ

L

104||6 104||6 GΩ||pF

−0.1 +VS − 2 −0.1 +VS − 2 V

800 800 kHz 120 120 kHz 14 14 kHz

2 2 V/μs

1 1000 1 1000 V/V

0.3 0.2 %

35 50 35 50 ppm 35 50 35 50 ppm 50 75 50 75 ppm

3 10 2 5 ppm/°C

−50 −50 ppm/°C

Rev. A | Page 6 of 28

AD8220

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A Grade B Grade Parameter Test Conditions Min Typ Max Min Typ Max Unit

OUTPUT

Output Swing RL = 2 kΩ 0.25 4.75 0.25 4.75 V

Over Temperature T = −40°C to +85°C 0.3 4.70 0.3 4.70 V

Output Swing RL = 10 kΩ 0.15 4.85 0.15 4.85 V

Over Temperature T = −40°C to +85°C 0.2 4.80 0.2 4.80 V

Short-Circuit Current

REFERENCE INPUT

R

IN

I

IN

Voltage Range Gain to Output

POWER SUPPLY

Operating Range 4.5 36 4.5 36 V Quiescent Current 750 750 μA

Over Temperature T = −40°C to +85°C 850 850 μA

TEMPERATURE RANGE

For Specified Performance −40 +85 −40 +85 °C Operational

1

When the output sinks more than 4 mA, use a 47 pF capacitor in parallel with the load to prevent ringing. Otherwise, use a larger load, such as 10 kΩ.

2

Differential and common-mode impedance can be calculated from the pin impedance: Z

3

The AD8220 can operate up to a diode drop below the negative supply but the bias current increases sharply. The input voltage range reflects the maximum

allowable voltage where the input bias current is within the specification.

4

The AD8220 is characterized from −40°C to +125°C. See the Typical Performance Characteristics section for expected operation in that temperature range.

4

VIN+, VIN− = 0 V

15 15 mA

40 40 kΩ 70 70 μA

−VS +V 1 ±

0.0001

S

−VS +V 1 ±

V/V

0.0001

S

V

−40 +125 −40 +125 °C

= 2(Z

DIFF

); ZCM = Z

/2.

Rev. A | Page 7 of 28

AD8220

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ABSOLUTE MAXIMUM RATINGS

Tabl e 3.

Parameter Rating

Supply Voltage ±18 V Power Dissipation See Figure 3 Output Short-Circuit Current Indefinite

1

Input Voltage (Common Mode) ±Vs Differential Input Voltage ±Vs Storage Temperature Range −65°C to +125°C Operating Temperature Range

2

−40°C to +125°C Lead Temperature (Soldering 10 sec) 300°C Junction Temperature 140°C θJA (4-Layer JEDEC Standard Board) 135°C/W Package Glass Transition Temperature 140°C ESD (Human Body Model) 4 kV ESD (Charge Device Model) 1 kV ESD (Machine Model) 0.4 kV

1

Assumes the load is referenced to midsupply.

2

Temperature for specified performance is −40°C to +85°C. For performance

to 125°C, see the Typical Performance Characteristics section.

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.

Figure 3 shows the maximum safe power dissipation in the p

ackage vs. the ambient temperature for the MSOP on a 4-layer

JEDEC standard board. θ

values are approximations.

JA

2.00

1.75

1.50

1.25

1.00

0.75

0.50

MAXIMUM POW ER DISSIPAT ION (W)

0.25

0

–40 120

–20 0 20 40 60 80 100

AMBIENT T EMPERATURE (°C)

Figure 3. Maximum Power Dissipation vs. Ambient Temperature

03579-045

ESD CAUTION

Rev. A | Page 8 of 28

AD8220

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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

AD8220

1

–IN

2

R

G

3

R

G

4

+IN

TOP VIEW

(Not to Scale)

Figure 4. Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 −IN Negative Input Terminal (True Differential Input) 2, 3 R

G

Gain Setting Terminals (Place Resistor Across the RG Pins) 4 +IN Positive Input Terminal (True Differential Input) 5 −V

S

Negative Power Supply Terminal 6 REF Reference Voltage Terminal (Drive This Terminal with a Low Impedance Voltage Source to Level-Shift the Output) 7 V 8 +V

OUT

S

Output Terminal

Positive Power Supply Terminal

8

+V

S

7

V

OUT

6

REF

5

–V

S

03579-005

Rev. A | Page 9 of 28

ANALOG DEVICES AD8220 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

PIN CONFIGURATION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

ESD CAUTION

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS