ANALOG DEVICES AD8426 Service Manual

Wide Supply Range, Rail-to-Rail

FEATURES

2 channels in a small, 4 mm × 4 mm LFCSP LFCSP package has no metal pad

More routing room No current leakage to pad

Gain set with 1 external resistor

Gain range: 1 to 1000 Input voltage goes below ground Inputs protected beyond supplies Very wide power supply range

Single supply: 2.2 V to 36 V

Dual supply: ±1.35 V to ±18 V Bandwidth (G = 1): 1 MHz CMRR (G = 1): 80 dB minimum Input noise: 24 nV/√Hz Typical supply current (per amplifier): 350 μA Specified temperature range: −40°C to +125°C

APPLICATIONS

Industrial process controls Bridge amplifiers Medical instrumentation Portable data acquisition Multichannel systems

GENERAL DESCRIPTION

The AD8426 is a dual-channel, low cost, wide supply range instrumentation amplifier that requires only one external resistor to set any gain from 1 to 1000.

The AD8426 is designed to work with a variety of signal voltages. A wide input range and rail-to-rail output allow the signal to make full use of the supply rails. Because the input range can also go below the negative supply, small signals near ground can be amplified without requiring dual supplies. The

AD8426 operates on supplies ranging from ±1.35 V to ±18 V

for dual supplies and 2.2 V to 36 V for a single supply.

The robust AD8426 inputs are designed to connect to realworld sensors. In addition to its wide operating range, the

AD8426 can handle voltages beyond the rails. For example,

with a ±5 V supply, the part is guaranteed to withstand ±35 V at the input with no damage. Minimum and maximum input bias currents are specified to facilitate open-wire detection.

Output Instrumentation Amplifier

AD8426

CONNECTION DIAGRAM

S

OUT2

13141516

REF1

REF2

Figure 1.

–V

S

–V

12

11

10

9

Low Power

–IN2

RG2

+IN2

09490-001

High Speed PGA

+VSOUT1

AD8426

1

–IN1

2

RG1

3

RG1

4

+IN1

5678

S

+V

Table 1. Instrumentation Amplifiers by Category1

GeneralPurpose

Zero Drift

Military Grade

AD8220 AD8231 AD620 AD627 AD8250 AD8221 AD8290 AD621 AD623 AD8251 AD8222 AD8293 AD524 AD8235 AD8253 AD8224 AD8553 AD526 AD8236 AD8228 AD8556 AD624 AD8426 AD8295 AD8557 AD8226

AD8227

1

See www.analog.com for the latest instrumentation amplifiers.

The AD8426 is designed to make PCB routing easy and efficient. The two amplifiers are arranged in a logical way so that typical application circuits have short routes and few vias. Unlike most chip scale packages, the AD8426 does not have an exposed metal pad on the bottom of the part, which frees additional space for routing and vias. The AD8426 offers two in-amps in the equivalent board space of a typical MSOP package.

The AD8426 is ideal for multichannel, space-constrained industrial applications. Unlike other low cost, low power instrumentation amplifiers, the AD8426 is designed with a minimum gain of 1 and can easily handle ±10 V signals. With its space-saving LFCSP package and 125°C temperature rating, the AD8426 thrives in tightly packed, zero airflow designs.

The AD8226 is the single-channel version of the AD8426.

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.

AD8426

REVISION HISTORY

7/11—Revision 0: Initial Version

Rev. 0 | Page 2 of 28

AD8426

SPECIFICATIONS

DUAL-SUPPLY OPERATION

+VS = +15 V, −VS = −15 V, V

Table 2.

Parameter Min Typ Max Min Typ Max Unit

COMMON-MODE REJECTION

RATIO (CMRR)

CMRR, DC to 60 Hz

G = 1 80 90 dB G = 10 100 105 dB G = 100 105 110 dB G = 1000 105 110 dB

CMRR at 5 kHz

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

NOISE

Voltage Noise f = 1 kHz

Input Voltage Noise, eNI 24 27 24 27 nV/√Hz Output Voltage Noise, eNO 120 125 120 125 nV/√Hz

RTI Noise 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 0.4 0.4 μV p-p

Current Noise f = 1 kHz 100 100 fA/√Hz

f = 0.1 Hz to 10 Hz 3 3 pA p-p VOLTAGE OFFSET

Input Offset, V

V

OSI

Average Temperature

Coefficient

Output Offset, V

V

OSO

Average Temperature

Coefficient

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

G = 1 80 90 dB G = 10 100 105 dB G = 100 105 110 dB G = 1000 105 110 dB

INPUT CURRENT

Input Bias Current

1

T

T T

Average Temperature

Coefficient

Input Offset Current TA = +25°C 1.5 0.5 nA

T T

Average Temperature

Coefficient

= 0 V, TA = 25°C, G = 1, RL = 10 k, specifications referred to input, unless otherwise noted.

REF

Test Conditions/

A Grade B Grade

Comments

= −10 V to +10 V

V

CM

Tot al noise: e

= √(e

N

2

+ (eNO/G)2)

NI

Total offset voltage: VOS = V

T

+ (V

OSO

/G)

OSI

= ±5 V to ±15 V 200 100 μV

S

= −40°C to +125°C 0.5 2 0.5 1 μV/°C

A

= ±5 V to ±15 V 1000 500 μV

S

= −40°C to +125°C 2 10 1 5 μV/°C

A

= +25°C 5 20 27 5 20 27 nA

A

= +125°C 5 15 25 5 15 25 nA

A

= −40°C 5 30 35 5 30 35 nA

A

= −40°C to +125°C 70 70 pA/°C

A

= +125°C 1.5 0.5 nA

A

= −40°C 2 0.5 nA

A

= −40°C to +125°C 5 5 pA/°C

A

Rev. 0 | Page 3 of 28

AD8426

Parameter Min Typ Max Min Typ Max Unit

Test Conditions/ Comments

REFERENCE INPUT

RIN 100 100 kΩ IIN 7 7 μA Voltage Range −VS +VS −VS +VS V Reference Gain to Output 1 1 V/V Reference Gain Error 0.01 0.01 %

GAIN G = 1 + (49.4 kΩ/RG)

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

± 10 V

OUT

G = 1 0.04 0.01 % G = 5 to 1000 0.3 0.1 %

Gain Nonlinearity V

= −10 V to +10 V

OUT

G = 1 to 10 RL ≥ 2 kΩ 20 20 ppm G = 100 RL ≥ 2 kΩ 75 75 ppm G = 1000 RL ≥ 2 kΩ 750 750 ppm

Gain vs. Temperature

2

G = 1 TA = −40°C to +85°C 5 1 ppm/°C T

= +85°C to +125°C 5 2 ppm/°C

A

G > 1 TA = −40°C to +125°C −100 −100 ppm/°C

INPUT VS = ±1.35 V to +36 V

Input Impedance

Differential 0.8||2 0.8||2 GΩ||pF Common Mode 0.4||2 0.4||2 GΩ||pF

Input Operating Voltage

Range

3

T T

TA = +25°C −VS − 0.1 +VS − 0.8 −VS − 0.1 +VS − 0.8 V

= +125°C −VS − 0.05 +VS − 0.6 −VS − 0.05 +VS − 0.6 V

A

= −40°C −VS − 0.15 +VS − 0.9 −VS − 0.15 +VS − 0.9 V

A

Input Overvoltage Range TA = −40°C to +125°C +VS − 40 −VS + 40 +VS − 40 −VS + 40 V

OUTPUT

Output Swing

RL = 2 kΩ to Ground TA = +25°C −VS + 0.4 +VS − 0.7 −VS + 0.4 +VS − 0.7 V T T

= +125°C −VS + 0.4 +VS − 1.0 −VS + 0.4 +VS − 1.0 V

A

= −40°C −VS + 1.2 +VS − 1.1 −VS + 1.2 +VS − 1.1 V

A

RL = 10 kΩ to Ground TA = +25°C −VS + 0.2 +VS − 0.2 −VS + 0.2 +VS − 0.2 V T T

= +125°C −VS + 0.3 +VS − 0.3 −VS + 0.3 +VS − 0.3 V

A

= −40°C −VS + 0.2 +VS − 0.2 −VS + 0.2 +VS − 0.2 V

A

RL = 100 kΩ to Ground TA = −40°C to +125°C −VS + 0.1 +VS − 0.1 −VS + 0.1 +VS − 0.1 V

Short-Circuit Current 13 13 mA

POWER SUPPLY

Operating Range Dual-supply operation ±1.35 ±18 ±1.35 ±18 V

= +25°C 350 425 350 425 μA

Quiescent Current

T

A

(Per Amplifier) T T T

= −40°C 250 325 250 325 μA

A

= +85°C 450 525 450 525 μA

A

= +125°C 525 600 525 600 μA

A

TEMPERATURE RANGE −40 +125 −40 +125 °C

1

The input stage uses PNP transistors; therefore, input bias current always flows into the part.

2

The values specified for G > 1 do not include the effects of the external gain-setting resistor, RG.

3

Input voltage range of the AD8426 input stage. The input range depends on the common-mode voltage, the differential voltage, the gain, and the reference voltage.

See the section for more information. Input Voltage Range

A Grade B Grade

Rev. 0 | Page 4 of 28

AD8426

Dynamic Performance Specifications

+VS = +15 V, −VS = −15 V, V

Table 3. Single-Ended Output Configuration (Both Amplifiers)

Parameter Min Typ Max Min Typ Max Unit

DYNAMIC RESPONSE

Small Signal −3 dB Bandwidth

G = 1 1000 1000 kHz G = 10 160 160 kHz G = 100 20 20 kHz G = 1000 2 2 kHz

Settling Time 0.01% 10 V step

G = 1 25 25 μs G = 10 15 15 μs G = 100 40 40 μs G = 1000 750 750 μs

Slew Rate

G = 1 0.4 0.4 V/μs G = 5 to 100 0.6 0.6 V/μs

= 0 V, TA = 25°C, G = 1, RL = 10 k, specifications referred to input, unless otherwise noted.

REF

Test Conditions/ Comments

A Grade B Grade

Table 4. Differential Output Configuration

Parameter Min Typ Max Min Typ Max Unit

DYNAMIC RESPONSE

Small Signal −3 dB Bandwidth

G = 1 850 850 kHz G = 10 300 300 kHz G = 100 30 30 kHz G = 1000 2 2 kHz

Settling Time 0.01% 10 V step

G = 1 25 25 μs G = 10 15 15 μs G = 100 80 80 μs G = 1000 300 300 μs

Slew Rate

G = 1 0.4 0.4 V/μs G = 5 to 100 0.6 0.6 V/μs

Test Conditions/ Comments

A Grade B Grade

Rev. 0 | Page 5 of 28

AD8426

SINGLE-SUPPLY OPERATION

+VS = 2.7 V, −VS = 0 V, V

Table 5.

Parameter Min Typ Max Min Typ Max Unit

COMMON-MODE REJECTION

RATIO (CMRR) CMRR, DC to 60 Hz

G = 1 80 90 dB G = 10 100 105 dB G = 100 105 110 dB G = 1000 105 110 dB

CMRR at 5 kHz

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

NOISE

Voltage Noise f = 1 kHz

Input Voltage Noise, eNI 24 27 24 27 nV/√Hz Output Voltage Noise, eNO 120 125 120 125 nV/√Hz

RTI Noise 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 0.4 0.4 μV p-p

Current Noise f = 1 kHz 100 100 fA/√Hz f = 0.1 Hz to 10 Hz 3 3 pA p-p VOLTAGE OFFSET

Input Offset, V

300 150 μV

OSI

Average Temperature

Coefficient

Output Offset, V

OSO

Average Temperature

Coefficient

Offset RTI vs. Supply (PSR) VS = 2.7 V to 36 V

G = 1 80 90 dB G = 10 100 105 dB G = 100 105 110 dB G = 1000 105 110 dB

INPUT CURRENT

Input Bias Current

1

T T

Average Temperature

Coefficient

Input Offset Current TA = +25°C 2 1 nA T T

Average Temperature

Coefficient

= 0 V, TA = 25°C, G = 1, RL = 10 k, specifications referred to input, unless otherwise noted.

REF

Test Conditions/

A Grade B Grade

Comments

V

= 0 V to 1.7 V

CM

Tot al noise: e

N

= √(e

2

+ (eNO/G)2)

NI

Total offset voltage:

= V

+ (V

V

OS

OSI

T

= −40°C to +125°C 0.5 3 0.5 1.5 μV/°C

A

OSO

/G)

1000 500 μV

= −40°C to +125°C 2 12 1 8 μV/°C

T

A

T

= +25°C 5 20 30 5 20 30 nA

A

= +125°C 5 15 28 5 15 28 nA

A

= −40°C 5 30 38 5 30 38 nA

A

= −40°C to +125°C 70 70 pA/°C

T

A

= +125°C 2 1 nA

A

= −40°C 3 1 nA

A

T

= −40°C to +125°C 5 5 pA/°C

A

Rev. 0 | Page 6 of 28

AD8426

Parameter Min Typ Max Min Typ Max Unit

Test Conditions/ Comments

REFERENCE INPUT

RIN 100 100 kΩ IIN 7 7 μA Voltage Range −VS +VS −VS +VS V Reference Gain to Output 1 1 V/V Reference Gain Error 0.01 0.01 %

GAIN G = 1 + (49.4 kΩ/RG)

Gain Range 1 1000 1 1000 V/V Gain Error

G = 1 V G = 5 to 1000 V

Gain vs. Temperature

2

= 0.8 V to 1.8 V 0.05 0.05 %

OUT

= 0.2 V to 2.5 V 0.3 0.1 %

OUT

G = 1 TA = −40°C to +85°C 5 1 ppm/°C T

= +85°C to +125°C 5 2 ppm/°C

A

G > 1 TA = −40°C to +125°C −100 −100 ppm/°C

INPUT

= 0 V, +VS = 2.7 V

−V

S

to 36 V

Input Impedance

Differential 0.8||2 0.8||2 GΩ||pF Common Mode 0.4||2 0.4||2 GΩ||pF

Input Operating Voltage

Range

3

T T

TA = +25°C −0.1 +VS − 0.7 −0.1 +VS − 0.7 V

= +125°C −0.05 +VS − 0.6 −0.05 +VS − 0.6 V

A

= −40°C −0.15 +VS − 0.9 −0.15 +VS − 0.9 V

A

Input Overvoltage Range TA = −40°C to +125°C +VS − 40 −VS + 40 +VS − 40 −VS + 40 V

OUTPUT

Output Swing

RL = 10 kΩ to 1.35 V TA = −40°C to +125°C 0.1 +VS − 0.1 0.1 +VS − 0.1 V

Short-Circuit Current 13 13 mA

POWER SUPPLY

Operating Range Single-supply operation 2.2 36 2.2 36 V

= 0 V, +VS = 2.7 V

Quiescent Current

−V

S

(Per Amplifier) T T T T

= +25°C 325 400 325 400 μA

A

= −40°C 250 325 250 325 μA

A

= +85°C 425 500 425 500 μA

A

= +125°C 475 550 475 550 μA

A

TEMPERATURE RANGE −40 +125 −40 +125 °C

1

The input stage uses PNP transistors; therefore, input bias current always flows into the part.

2

The values specified for G > 1 do not include the effects of the external gain-setting resistor, RG.

3

Input voltage range of the AD8426 input stage. The input range depends on the common-mode voltage, the differential voltage, the gain, and the reference voltage.

See the section for more information. Input Voltage Range

A Grade B Grade

Rev. 0 | Page 7 of 28

AD8426

Dynamic Performance Specifications

+VS = 2.7 V, −VS = 0 V, V

Table 6. Single-Ended Output Configuration (Both Amplifiers)

Parameter Min Typ Max Min Typ Max Unit

DYNAMIC RESPONSE

Small Signal −3 dB Bandwidth

G = 1 1000 1000 kHz G = 10 160 160 kHz G = 100 20 20 kHz G = 1000 2 2 kHz

Settling Time 0.01% 2 V step

G = 1 6 6 μs G = 10 6 6 μs G = 100 35 35 μs G = 1000 750 750 μs

Slew Rate

G = 1 0.4 0.4 V/μs G = 5 to 100 0.6 0.6 V/μs

= 0 V, TA = 25°C, G = 1, RL = 10 k, specifications referred to input, unless otherwise noted.

REF

Test Conditions/ Comments

A Grade B Grade

Table 7. Differential Output Configuration

Parameter Min Typ Max Min Typ Max Unit

DYNAMIC RESPONSE

Small Signal −3 dB Bandwidth

G = 1 850 850 kHz G = 10 300 300 kHz G = 100 30 30 kHz G = 1000 2 2 kHz

Settling Time 0.01% 2 V step

G = 1 25 25 μs G = 10 15 15 μs G = 100 80 80 μs G = 1000 300 300 μs

Slew Rate

G = 1 0.4 0.4 V/μs G = 5 to 100 0.6 0.6 V/μs

Test Conditions/ Comments

A Grade B Grade

Rev. 0 | Page 8 of 28

AD8426

ABSOLUTE MAXIMUM RATINGS

Table 8.

Parameter Rating

Supply Voltage ±18 V Output Short-Circuit Current Indefinite Maximum Voltage at −INx or +INx −VS + 40 V Minimum Voltage at −INx or +INx +VS − 40 V REFx Voltage ±VS Storage Temperature Range −65°C to +150°C Specified Temperature Range −40°C to +125°C Maximum Junction Temperature 130°C ESD

Human Body Model 1.5 kV Charged Device Model 1.5 kV Machine Model 100 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 RESISTANCE

The θJA value in Tabl e 9 assumes a 4-layer JEDEC standard board with zero airflow.

Table 9.

Package θJA Unit

16-Lead LFCSP (CP-16-19) 86 °C/W

ESD CAUTION

Rev. 0 | Page 9 of 28

ANALOG DEVICES AD8426 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

CONNECTION DIAGRAM

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

DUAL-SUPPLY OPERATION

Dynamic Performance Specifications

SINGLE-SUPPLY OPERATION

Dynamic Performance Specifications

ABSOLUTE MAXIMUM RATINGS

THERMAL RESISTANCE

ESD CAUTION