ANALOG DEVICES AD8295 Service Manual

Precision Instrumentation Amplifier

V

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FEATURES

Saves board space Includes precision in-amp, 2 op amps, and

2 matched resistors 4 mm × 4 mm LFCSP No heat slug for more routing room Differential output fully specified In-amp specifications

Gain set with 1 external resistor (gain range: 1 to 1000)

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

90 dB minimum CMRR (G = 1)

0.8 nA maximum input bias current

1.2 MHz, −3 dB bandwidth (G = 1)

2 V/μs slew rate Wide power supply range: ±2.3 V to ±18 V 1 ppm/°C, 0.03% resistor matching

APPLICATIONS

Industrial process controls Wheatstone bridges Precision data acquisition systems Medical instrumentation Strain gages Transducer interfaces Differential output

GENERAL DESCRIPTION

The AD8295 contains all the components necessary for a precision instrumentation amplifier front end in one small 4 mm × 4 mm package. It contains a high performance instrumentation amplifier, two general-purpose operational amplifiers, and two precisely matched 10 k resistors.

The AD8295 is designed to make PCB routing easy and efficient. The AD8295 components are arranged in a logical way so that typical application circuits have short routes and few vias. Unlike most chip scale packages, the AD8295 does not have an exposed metal pad on the back of the part, which frees additional space for routing and vias. The AD8295 comes in a 4 mm × 4 mm LFCSP that requires half the board space of an 8-pin SOIC package.

with Signal Processing Amplifiers

AD8295

CONNECTION DIAGRAM

+

OUT

IA

REF

Military Grade

A2 +IN A2 –IN

A2

A1

A1 OUT A1 R2

Figure 1.

13141516

R1 20kΩ

R2 20kΩ

8765

Low Power

12

11

10

9

A2 OUT

A1 +IN

A1 R1

A1 –IN

07343-001

High Speed PGA

S

AD8295

1

–IN

R

2

G

R

3

G

4

+IN

–V

S

Table 1. Instrumentation Amplifiers by Category

General Purpose

Zero Drift

AD82201 AD82311 AD620 AD6271 AD8250 AD8221 AD85531 AD621 AD6231 AD8251 AD8222 AD85551 AD524 AD82231 AD8253 AD82241 AD85561 AD526 AD8228 AD85571 AD624 AD8295 AD82931

1

Rail-to-rail output.

The AD8295 includes a high performance, programmable gain instrumentation amplifier. Gain is set from 1 to 1000 with a single resistor. The low noise and excellent common-mode rejection of the AD8295 enable the part to easily detect small signals even in the presence of large common-mode interference. For a similar instrumentation amplifier without the associated signal conditioning circuitry, see the AD8221 or AD8222 data sheet.

The AD8295 operates on both single and dual supplies and is well suited for applications where ±10 V input voltages are encountered. Performance is specified over the entire industrial temperature range of −40°C to +85°C for all grades. The AD8295 is operational from −40°C to +125°C; see the Ty pi ca l Performance Characteristics section for expected operation up to 125°C.

Rev. 0

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.

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REVISION HISTORY

10/08—Revision 0: Initial Version

Rev. 0 | Page 2 of 28

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SPECIFICATIONS

INSTRUMENTATION AMPLIFIER SPECIFICATIONS, SINGLE-ENDED AND DIFFERENTIAL OUTPUT CONFIGURATIONS

VS = ±15 V, V

Table 2.

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

COMMON-MODE REJECTION

RATIO (CMRR)

CMRR, DC to 60 Hz 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 8 kHz

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

NOISE

Voltage Noise, 1 kHz

Input Voltage Noise, eNI V Output Voltage Noise, eNO V

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 RTI VOS = (V

Input Offset, V

Over Temperature TA = −40°C to +85°C 150 80 μV Average TC 0.4 0.3 μV/°C

Output Offset, V

Over Temperature TA = −40°C to +85°C 0.8 0.5 mV Average TC 9 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 2.0 0.2 0.8 nA

Over Temperature TA = −40°C to +85°C 3.0 1.5 nA Average TC 1 1 pA/°C

Input Offset Current 0.2 1 0.1 0.5 nA

Over Temperature TA = −40°C to +85°C 1.5 0.6 nA Average TC 1 0.5 2 pA/°C

= 0 V, TA = 25°C, G = 1, RL = 2 kΩ, unless otherwise noted. The differential configuration is shown in Figure 59.

REF

= −10 V to +10 V

V

CM

RTI noise =

2

+ (eNO/G)2)

√(e

NI

, V

IN+

, V

IN+

V

OSI

V

OSO

= ±5 V to ±15 V 120 60 μV

S

= ±5 V to ±15 V 500 350 μV

S

= 0 V 8 8 nV/√Hz

IN−

REF

, V

= 0 V 75 75 nV/√Hz

IN−

REF

) + (V

OSI

OSO

/G)

Rev. 0 | Page 3 of 28

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

GAIN G = 1 + (49.4 kΩ/RG)

Gain Range 1 1000 1 1000 V/V Gain Error V

G = 1 0.05 0.02 % G = 10 0.3 0.1 % G = 100 0.3 0.1 % G = 1000 0.3 0.1 %

Gain Nonlinearity V

G = 1 3 10 1 5 ppm G = 10 7 20 7 20 ppm G = 100 7 20 7 20 ppm

Gain vs. Temperature

G = 1 5 1 ppm/°C G > 1 −50 −50 ppm/°C

DYNAMIC RESPONSE (SINGLE-

ENDED CONFIGURATION) Small Signal −3 dB Bandwidth

G = 1 1200 1200 kHz G = 10 750 750 kHz G = 100 140 140 kHz G = 1000 15 15 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 1000 2 2.5 2 2.5 V/μs

DYNAMIC RESPONSE (DIFFERENTIAL

OUTPUT CONFIGURATION) Small Signal −3 dB Bandwidth

G = 1 1200 1200 kHz G = 10 1000 1000 kHz G = 100 140 140 kHz G = 1000 15 15 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 1000 2 2.5 2 2.5 V/μs

REFERENCE INPUT

RIN 20 20 kΩ IIN V Voltage Range −VS +VS −VS +VS V Gain to Output 1 ± 0.0001 1 ± 0.0001 V/V

± 10 V

OUT

= −10 V to +10 V

OUT

, V

IN+

= 0 V 50 60 50 60 μA

IN−

REF

Rev. 0 | Page 4 of 28

AD8295

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

INPUT

Input Impedance

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

Input Operating Voltage Range

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

Input Operating Voltage Range

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

Short-Circuit Current 18 18 mA

1

One input grounded; G = 1.

OP AMP SPECIFICATIONS

VS = ±15 V, TA = 25°C, RL = 2 kΩ, unless otherwise noted.

1

V

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

S

1

V

= ±5 V to ±18 V −VS + 1.9 +VS − 1.2 −VS + 1.9 +VS − 1.2 V

S

Table 3.

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

INPUT CHARACTERISTICS

Offset Voltage, VOS 40 20 μV

Average TC TA = −40°C to +85°C 4 2 μV/°C

Input Bias Current

T T

1

10 8 nA

= −40°C 20 16 nA

A

= +85°C 10 8 nA

A

Input Offset Current 2 0.5 nA

Over Temperature TA = −40°C to +85°C 2 0.5 nA Input Voltage Range −VS + 1.2 +VS − 1.2 −VS + 1.2 +VS − 1.2 V Open-Loop Gain 100 125 116 125 dB Common-Mode Rejection Ratio 100 100 dB Power Supply Rejection Ratio 90 110 94 110 dB Voltage Noise Density 40 40 nV/√Hz Voltage Noise f = 0.1 Hz to 10 Hz 2.2 2.2 μV p-p

DYNAMIC PERFORMANCE

Gain Bandwidth Product 1 1 MHz Slew Rate 2.6 2.6 V/μs

OUTPUT CHARACTERISTICS

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

Over Temperature TA = −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 TA = −40°C to +85°C −VS + 1.6 +VS − 1.5 −VS + 1.6 +VS − 1.5 V Short-Circuit Current 18 18 mA

1

Op amp uses an npn input stage, so input bias current always flows into the inputs.

Rev. 0 | Page 5 of 28

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INTERNAL RESISTOR NETWORK

When used with internal Op Amp A1, TA = 25°C, unless otherwise noted. Use in external op amp feedback loops is not recommended.

Table 4.

Parameter Test Conditions Min Typ Max Min Typ Max Unit

Nominal Resistor Value 20 20 kΩ Resistor Matching 0.1 0.03 % Matching Temperature Coefficient TA = −40°C to +85°C 5 1 ppm/°C Absolute Resistor Accuracy 0.2 0.1 % Absolute Temperature Coefficient TA = −40°C to +85°C −50 −50 ppm/°C

A Grade B Grade

POWER AND TEMPERATURE SPECIFICATIONS

VS = ±15 V, V

Table 5.

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

POWER SUPPLY

Operating Range ±2.3 ±18 ±2.3 ±18 V Quiescent Current In-amp + two op amps 2 2.3 2 2.3 mA

Over Temperature TA = −40°C to +85°C 2.5 2.5 mA

TEMPERATURE RANGE

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

1

See the section for expected operation from 85°C to 125°C. Typical Performance Characteristics

= 0 V, TA = 25°C, unless otherwise noted.

REF

1

−40 +125 −40 +125 °C

Rev. 0 | Page 6 of 28

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ABSOLUTE MAXIMUM RATINGS

Table 6.

Parameter Rating

Supply Voltage ±18 V Output Short-Circuit Current Indefinite Input Voltage

Common-Mode ±VS Differential ±VS

Storage Temperature Range −65°C to +130°C Operating Temperature Range1 −40°C to +125°C Lead Temperature (Soldering, 10 sec) 300°C Junction Temperature 130°C ESD (Human Body Model) 2000 V ESD (Charge Device Model) 500 V ESD (Machine Model) 200 V

1

Temperature range for specified performance is −40°C to +85°C. See the

Typical Performance Characteristics section for expected operation from 85°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

Specifications are provided for a device in free air.

Table 7.

Package θJA Unit

16-Lead LFCSP_VQ 86 °C/W

ESD CAUTION

Rev. 0 | Page 7 of 28

AD8295

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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

S

A2 –IN

OUT

+V

A2 +IN

14

13

15

16

PIN 1 INDICATO R

1–IN

2R

G

AD8295

3R

G

TOP VIEW

4+IN

(Not to Scale)

5

6

S

–V

REF

Figure 2. Pin Configuration

Table 8. Pin Function Descriptions

Pin No. Mnemonic Description

1 −IN In-Amp Negative Input. 2, 3 RG In-Amp Gain-Setting Resistor Terminals. 4 +IN In-Amp Positive Input. 5 −VS Negative Supply. 6 REF In-Amp Reference Terminal. Drive with a low impedance source. Output is referred to this pin. 7 A1 OUT Op Amp A1 Output. 8 A1 R2 Resistor R2 Terminal. Connected internally to Op Amp A1 inverting input. 9 A1 −IN Op Amp A1 Inverting Input. Midpoint of resistor divider. 10 A1 R1 Resistor R1 Terminal. Connected internally to Op Amp A1 inverting input. 11 A1 +IN Op Amp A1 Noninverting Input. 12 A2 OUT Op Amp A2 Output. 13 A2 −IN Op Amp A2 Inverting Input. 14 A2 +IN Op Amp A2 Noninverting Input. 15 OUT In-Amp Output. 16 +VS Positive Supply.

12 A2 OUT

11 A1 +IN

10 A1 R1

9 A1 –I N

8

7

1 R2 A

A1 OUT

07343-017

Rev. 0 | Page 8 of 28

AD8295

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TYPICAL PERFORMANCE CHARACTERISTICS

IN-AMP

VS = ±15 V, REF = 0 V, TA = 25°C, RL = 10 kΩ, unless otherwise noted.

800

600

HITS

400

200

0

–100 –50 0 50 100

CMRR (µV/V)

Figure 3. Typical Distribution for CMRR, G = 1

800

700

600

500

400

HITS

300

200

100

0

–100 –50 0 50 100

V

(µV)

OSI

Figure 4. Typical Distribution of Input Offset Voltage

700

600

800

600

HITS

400

200

0

–1.0 –0.5 0 0.5 1.0

07343-057

INPUT OFF SET CURRENT (n A)

07343-060

Figure 6. Typical Distribution of Input Offset Current

5

4

3

2

1

0

–1

–2

INPUT COMMON-MODE VOLTAGE (V)

–3

–4

–5 –4 –3 –2 –1 0 1 2 3 4 5

07343-058

OUTPUT VOLTAGE (V)

G = 1 V

= ±2.5V, ±5V

S

07343-045

Figure 7. Input Common-Mode Range vs. Output Voltage, G = 1,

V

= ±2.5 V, ±5 V, REF = 0 V

S

15

10

G = 1 V

S

= ±15V

500

400

HITS

300

200

100

0

–2 –1 0 1 2

INPUT BIAS CURRENT (nA)

Figure 5. Typical Distribution of Input Bias Current

07343-059

5

0

–5

–10

INPUT COMMON-MODE VOLTAGE (V)

–15

–15 –10 –5 0 5 10 15

Figure 8. Input Common-Mode Range vs. Output Voltage, G = 1,

Rev. 0 | Page 9 of 28

OUTPUT VOLTAGE (V)

= ±15 V, REF = 0 V

V

S

07343-046

ANALOG DEVICES AD8295 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

CONNECTION DIAGRAM

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

INSTRUMENTATION AMPLIFIER SPECIFICATIONS, SINGLE-ENDED AND DIFFERENTIAL OUTPUT CONFIGURATIONS

OP AMP SPECIFICATIONS

INTERNAL RESISTOR NETWORK

POWER AND TEMPERATURE SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

THERMAL CHARACTERISTICS

ESD CAUTION

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

TYPICAL PERFORMANCE CHARACTERISTICS

IN-AMP