ANALOG DEVICES AD8235 Service Manual

40 μA Micropower Instrumentation

FEATURES

Low power

40 A maximum supply current 6 nA shutdown current

Low input currents

50 pA input bias current 25 pA input offset current

High Common Mode Rejection Ratio (CMRR)

110 dB CMRR , G = 100

Space saving

WLCSP package Zero input crossover distortion Versati le

Rail-to-rail input and output

Shutdown

Gain set with single resistor (G = 5 to 200) AD8236: µSOIC package version of AD8235

APPLICATIONS

Medical instrumentation Low-side current sense Portable electronics

GENERAL DESCRIPTION

The AD8235 is the smallest and lowest power instrumentation amplifier in the industry. It is available in a 1.5 mm × 2.2 mm wafer level chip scale package (WLCSP). The AD8235 draws a maximum quiescent current of 40 µA. In addition, it draws a maximum 500 nA of current during shutdown mode, making it an excellent instrumentation amplifier for battery powered, portable applications.

The AD8235 can operate on supply voltages as low as 1.8 V. The input stage allows for wide rail-to-rail input voltage range without the crossover distortion, common in other designs. The rail-torail output enables easy interfacing to ADCs.

The AD8235 is an excellent choice for signal conditioning. Its low input bias current of 50 pA and high CMRR of 110 dB (G = 100) offer tremendous value for its size and low power.

It is specified over the extended industrial temperature range of

−40°C to 125°C.

Amplifier in WLCSP Package

AD8235

CONNECTION DIAGRAM

R

REF

NC

C1

B2

D2

ESD

PROTECTION

G

B3 A1 D1

ESD

PROTECTION

210k 210k52.5k 52.5k

OP AMP

A

ESD

PROTECTION

A3 D3

–IN

RGRG

C3

ESD

PROTECTIO N

OP AMP

ESD

PROTECTIO N

+IN

B

Figure 1.

PIN CONFIGURATION

BALL A1 INDICATOR

1

23

+V

S

A

V

OUT

B

REF

C

–V

S

D

(BALL SIDE DOW N)

Not to Scal e

NC = NO CONNECT

Figure 2. 11-Ball WLCSP (CB-11-1)

5.0

4.5

(V)

4.0

3.5

3.0

2.5

2.0

1.5

1.0

INPUT COMMON-MODE VOLTAGE

0.5

G = 5 V

= 5V

S

V

= 2.5V

REF

G = 5

= 1.8V

V

S

V

= 0.9V

REF

0

OUTPUT VOLTAGE (V)

Figure 3. Wide Common-Mode Voltage Range vs. Output Voltage

SDN

NC

TOP VIEW

–IN

RG

+IN

08211-004

+V

S

ESD

PROTECTION

AD8235

–V

S

A2

B1

5.55.00.5–0.5 1.5 2.0 3.0 4.0 4.50 1.0 2.5 3.5

SDN

V

OUT

8211-001

8211-002

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.

AD8235

REVISION HISTORY

8/09—Revision 0: Initial Version

Rev. 0 | Page 2 of 20

AD8235

SPECIFICATIONS

+VS = 5 V, −VS = 0 V (GND), V

Table 1.

Parameter Test Conditions Min Typ Max Unit

COMMON-MODE REJECTION RATIO (CMRR) VS = ±2.5 V, V

CMRR DC VCM = −1.8 V to +1.8 V

G = 5 90 94 dB G = 10 90 100 dB G = 100 100 110 dB G = 200 100 110 dB

NOISE

Voltage Noise Spectral Density, RTI f = 1 kHz, G = 5 76 nV/√Hz

RTI, 0.1 Hz to 10 Hz

G = 5 4 μV p-p G = 200 4 μV p-p

Current Noise 15 fA/√Hz

VOLTAGE OFFSET

Input Offset, VOS 2.5 mV

Average Temperature Coefficient (TC) −40°C to +125°C 0.7 μV/°C

Offset RTI vs. Supply (PSR) VS = 1.8 V to 5 V

G = 5 100 120 dB G = 10 110 126 dB G = 100 110 130 dB G = 200 110 130 dB

INPUT CURRENT

Input Bias Current 1 50 pA

Overtemperature −40°C to +85°C 100 pA

−40°C to +125°C 600 pA

Input Offset Current 0.5 25 pA

Overtemperature −40°C to +85°C 50 pA

−40°C to +125°C 130 pA

DYNAMIC RESPONSE

Small Signal Bandwidth, −3 dB

G = 5 23 kHz G = 10 9 kHz G = 100 0.8 kHz G = 200 0.4 kHz

Settling Time 0.01% V

G = 5 444 μs G = 10 456 μs G = 100 992 μs G = 200 1816 μs

Slew Rate

G = 5 to 100 9 mV/μs

= 2.5 V, TA = 25°C, G = 5, R

REF

= 4 V step

OUT

= 100 k to GND, SDN pin tied to +VS, unless otherwise noted.

LOAD

= 0 V

REF

Rev. 0 | Page 3 of 20

AD8235

Parameter Test Conditions Min Typ Max Unit

GAIN

Gain Range G = 5 + 420 kΩ/RG 5 200 Gain Error VS = ±2.5 V, V

= 0 V, V

REF

= −2 V to +2 V

OUT

G = 5 0.005 0.05 % G = 10 0.03 0.2 % G = 100 0.06 0.2 % G = 200 0.15 0.3 %

Nonlinearity RL = 10 kΩ or 100 kΩ

G = 5 2 10 ppm G = 10 1.2 10 ppm G = 100 0.5 10 ppm G = 200 0.5 10 ppm

Gain vs. Temperature −40°C to +125°C

G = 5 0.35 1.5 ppm/°C G > 10 −50 ppm/°C

INPUT

Differential Impedance 440||1.6 GΩ||pF Common-Mode Impedance 110||6.2 GΩ||pF Input Voltage Range −40°C to +125°C 0 +VS V

OUTPUT

Output Voltage High, VOH R

= 100 kΩ 4.98 4.99 V

L

−40°C to +125°C 4.98 V R

= 10 kΩ 4.9 4.95 V

L

−40°C to +125°C 4.9 V Output Voltage Low, VOL R

= 100 kΩ 2 5 mV

L

−40°C to +125°C 5 mV R

= 10 kΩ 10 25 mV

L

−40°C to +125°C 30 mV Short-Circuit Limit, ISC ±55 mA

REFERENCE INPUT

RIN −IN, +IN = 0 V 210 kΩ IIN 20 nA Voltage Range −VS +VS V Gain to Output 1 V/V

SHUTDOWN OPERATION

Shutdown current 6 500 nA

−40°C to +125°C 1.5 μA SDN PIN INPUT VOLTAGE RANGE

VOH −40°C to +125°C +VS − 0.5 +VS V VOL −40°C to +125°C −VS −VS + 0.5 V

POWER SUPPLY

Operating Range 1.8 5.5 V Quiescent Current 30 40 μA Overtemperature −40°C to +125°C 50 μA

TEMPERATURE RANGE

For Specified Performance −40 +125 °C

1

Although the specifications of the AD8235 list only low to midrange gains, gains can be set beyond 200.

1

V/V

Rev. 0 | Page 4 of 20

AD8235

+VS = 1.8 V, −VS = 0 V (GND), V

Table 2.

Parameter Test Conditions Min Typ Max Unit

COMMON-MODE REJECTION RATIO (CMRR) VS = ±0.9 V, V

CMRR DC VCM = −0.6 V to +0.6 V

G = 5 90 94 dB G = 10 90 100 dB G = 100 100 110 dB G = 200 100 110 dB

NOISE

Voltage Noise Spectral Density, RTI f = 1 kHz, G = 5 76 nV/√Hz

RTI, 0.1 Hz to 10 Hz

G = 5 4 μV p-p G = 200 4 μV p-p

Current Noise 15 fA/√Hz

VOLTAGE OFFSET

Input Offset, VOS 2.5 mV

Average Temperature Coefficient (TC) −40°C to +125°C 0.7 μV/°C

Offset RTI vs. Supply (PSR) VS = 1.8 V to 5 V

G = 5 100 120 dB G = 10 110 126 dB G = 100 110 130 dB G = 200 110 130 dB

INPUT CURRENT

Input Bias Current 1 50 pA

Overtemperature −40°C to +85°C 100 pA

−40°C to +125°C 600 pA

Input Offset Current 0.5 25 pA

Overtemperature −40°C to +85°C 50 pA

−40°C to +125°C 130 pA

DYNAMIC RESPONSE

Small Signal Bandwidth, –3 dB

G = 5 23 kHz G = 10 9 kHz G = 100 0.8 kHz G = 200 0.4 kHz

Settling Time 0.01% V

G = 5 143 μs G = 10 178 μs G = 100 1000 μs G = 200 1864 μs

Slew Rate

G = 5 to 100 11 mV/μs

= 0.9 V, TA = 25°C, G = 5, R

REF

= 1.4 V step

OUT

= 100 k to GND, SDN pin tied to +VS, unless otherwise noted.

LOAD

= 0 V

REF

Rev. 0 | Page 5 of 20

AD8235

Parameter Test Conditions Min Typ Max Unit

GAIN

Gain Range G = 5 + 420 kΩ/RG 5 200 Gain Error VS = ±0.9 V, V

= 0 V, V

REF

= −0.6 V to +0.6 V

OUT

G = 5 0.005 0.05 % G = 10 0.03 0.2 % G = 100 0.06 0.2 % G = 200 0.15 0.3 %

Nonlinearity RL = 10 kΩ or 100 kΩ

G = 5 1 10 ppm G = 10 1 10 ppm G = 100 0.5 10 ppm G = 200 0.4 10 ppm

Gain vs. Temperature −40°C to +125°C

G = 5 0.35 1.5 ppm/°C G > 10 −50 ppm/°C

INPUT

Differential Impedance 440||1.6 GΩ||pF Common-Mode Impedance 110||6.2 GΩ||pF Input Voltage Range −40°C to +125°C 0 +VS V

OUTPUT

Output Voltage High, VOH R

= 100 kΩ 1.78 1.79 V

L

−40°C to +125°C 1.78 V R

= 10 kΩ 1.65 1.75 V

L

−40°C to +125°C 1.65 V Output Voltage Low, VOL R

= 100 kΩ 2 5 mV

L

−40°C to +125°C 5 mV R

= 10 kΩ 12 25 mV

L

−40°C to +125°C 25 mV Short-Circuit Limit, ISC ±6 mA

REFERENCE INPUT

RIN −IN, +IN = 0 V 210 kΩ IIN 20 nA Voltage Range −VS +VS V Gain to Output 1 V/V

SHUTDOWN OPERATION

Shutdown Current 6 500 nA

−40°C to +125°C 1.5 μA SDN PIN INPUT VOLTAGE RANGE

VOH −40°C to +125°C +VS − 0.5 +VS V VOL −40°C to +125°C −VS −VS + 0.5 V

TEMPERATURE RANGE

For Specified Performance −40 +125 °C

1

Although the specifications of the AD8235 list only low to midrange gains, gains can be set beyond 200.

1

V/V

Rev. 0 | Page 6 of 20

ANALOG DEVICES AD8235 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

CONNECTION DIAGRAM

PIN CONFIGURATION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS