ANALOG DEVICES AD8208 Service Manual

High Voltage,

V

FEATURES

Qualified for automotive applications
EMI filters included
High common-mode voltage range

−2 V to +45 V operating

−24 V to +80 V survival
Buffered output voltage
Gain = 20 V/V
Low-pass filter (1-pole or 2-pole)
Wide operating temperature range

8-lead SOIC: −40°C to +125°C
8-lead MSOP: −40°C to +125°C

Excellent ac and dc performance

±1 mV voltage offset

−5 ppm/°C typical gain drift

80 dB CMRR minimum dc to 10 kHz

APPLICATIONS

High-side current sensing

Motor controls
Solenoid controls

Power management
Low-side current sensing
Diagnostic protection

Precision Difference Amplifier

AD8208

FUNCTIONAL BLOCK DIAGRAM

S

A1 A2

EMI

FILTER

+IN

–IN

EMI

FILTER

EMI

FILTER

+

–

GND

Figure 1.

+

G = 2G = 10

–

AD8208

OUT

08714-001

GENERAL DESCRIPTION

The AD8208 is a single-supply difference amplifier ideal for
amplifying and low-pass filtering small differential voltages in the
presence of a large common-mode voltage. The input common­mode voltage range extends from −2 V to +45 V at a single +5 V
supply. The AD8208 is qualified for automotive applications. The
amplifier offers enhanced input overvoltage and ESD protection,
and includes EMI filtering.

Rev. A

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.

Automotive applications demand robust, precision components for
improved system control. The AD8208 provides excellent ac and dc
performance, minimizing errors in the application. Typical offset
and gain drift in both the SOIC and MSOP packages are less
than 5 µV/°C and 10 ppm/°C, respectively. The device also
delivers a minimum CMRR of 80 dB from dc to 10 kHz.

The AD8208 features an externally accessible 100 kΩ resistor at
the output of the preamplifier (A1), which can be used for low­pass filtering and for establishing gains other than 20.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2010 Analog Devices, Inc. All rights reserved.

AD8208

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1 

Functional Block Diagram .............................................................. 1

General Description ......................................................................... 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 4

ESD Caution .................................................................................. 4

Pin Configuration and Function Descriptions ............................. 5

Typical Performance Characteristics ............................................. 6

Theory of Operation ...................................................................... 10

REVISION HISTORY

5/10—Rev. 0 to Rev. A

Added 8-Lead MSOP ......................................................... Universal

Changes to Features Section and General Description Section . 1

Updated Outline Dimensions ....................................................... 15

Changes to Ordering Guide .......................................................... 15

1/10—Revision 0: Initial Version

Applications Information .............................................................. 11

High-Side Current Sensing with a Low-Side Switch ............. 11

High-Rail Current Sensing ....................................................... 11

Low-Side Current Sensing ........................................................ 11

Gain Adjustment ........................................................................ 12

Gain Trim .................................................................................... 12

Low-Pass Filtering ...................................................................... 13

High Line Current Sensing with LPF and Gain Adjustment ...... 14

Outline Dimensions ....................................................................... 15

Ordering Guide .......................................................................... 15

Rev. A | Page 2 of 16

AD8208

SPECIFICATIONS

T

= −40°C to +125°C, TA = 25°C, VS = 5 V, RL = 25 k (RL is the output load resistor), unless otherwise noted. Specifications applicable

OPR

for both packages (SOIC and MSOP).

Table 1.

Parameter Test Conditions1 Min Typ Max Unit

SYSTEM GAIN

Initial 20 V/V

Error vs. Temperature 0.075 V ≤ V

Gain Drift T

OPR

VOLTAGE OFFSET

Initial Input Offset (Referred to Input [RTI]) VCM = 0.15 V, TA ±2 mV

Input Offset (RTI) Over Temperature VCM = 0 V, T

Voltage Offset vs. Temperature VCM = 0 V, T

INPUT

Input Impedance

Differential 360 400 440 kΩ

Common Mode 180 200 220 kΩ
VCM (Continuous) −2 +45 V
CMRR2 V

= −2 V to +45 V, dc 80 100 dB

CM

f = dc to 10 kHz,3 T

PREAMPLIFIER (A1)

Gain 10 V/V
Gain Error 0.05 V ≤ V
Output Voltage Range 0.05 VS − 0.1 V
Output Resistance 97 100 103 kΩ

OUTPUT BUFFER (A2)

Gain 2 V/V
Gain Error 0.075 V ≤ V
Output Voltage Range4 R
Input Bias Current T

= 25 kΩ, differential Input (V) = 0 V, T

L

50 nA

OPR

Output Resistance RL = 1 kΩ, frequency = dc 2 Ω

DYNAMIC RESPONSE

System Bandwidth VIN = 0.01 V p-p, V
Slew Rate VIN = 0.28 V, V

NOISE

0.1 Hz to 10 Hz 20 μV p-p
Spectral Density, 1 kHz (RTI) 500 nV/√Hz

POWER SUPPLY

Operating Range 4.5 5.5 V
Quiescent Current Typical, TA 1.6 mA
Quiescent Current vs. Temperature V

= 0.1 V dc, VS = 5 V, T

OUT

PSRR VS = 4.5 V to 5.5 V, T

TEMPERATURE RANGE For Specified Performance at T

1

VCM = input common-mode voltage.

2

Source imbalance < 2 Ω.

3

The AD8208 preamplifier exceeds 80 dB CMRR at 10 kHz. However, because the output is available only by way of the 100 kΩ resistor, even a small amount of pin-to-

pin capacitance between the IN pins and the A1 and A2 pins might couple an input common-mode signal larger than the greatly attenuated preamplifier output. The
effect of pin-to-pin coupling can be negated in all applications by using a filter capacitor from Pin 3 to GND.

4

The output voltage range of the AD8208 varies depending on the load resistance and temperature. For additional information on this specification, see F and

Figure 13.

≤ (VS − 0.1 V), dc, T

OUT

±0.3 %

OPR

0 −20 ppm/°C

±4 mV

OPR

−20 +20 μV/°C

OPR

80 dB

OPR

≤ (VS − 0.1 V), dc, T

OUT

≤ (VS − 0.1 V), dc, T

OUT

= 0.14 V p-p 70 kHz

OUT

= 4 V step 1 V/μs

OUT

OPR

66 80 dB

OPR

−0.3 +0.3 %

OPR

−0.3 +0.3 %

OPR

0.075 VS − 0.1 V

OPR

2.7 mA

−40 +125 °C

OPR

igure 12

Rev. A | Page 3 of 16

AD8208

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Supply Voltage 12 V
Continuous Input Voltage (Common Mode) −24 V to +80 V
Differential Input Voltage ±12 V
Reversed Supply Voltage Protection 0.3 V
ESD Human Body Model ±4000 V
Operating Temperature Range −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Output Short-Circuit Duration Indefinite
Lead Temperature Range (Soldering, 10 sec) 300°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.

ESD CAUTION

Rev. A | Page 4 of 16

AD8208

G

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

–IN

1

AD8208

2

ND

TOP VIEW

A1

3

(Not to Scale)

A2

4

NC = NO CONNECT

+IN

8

7

NC

6

V

S

OUT

5

08714-002

Figure 2. Pin Configuration

Table 3. Pin Function Descriptions

Coordinates
Pin No. Mnemonic X Y Description

1 −IN −322 +563 Inverting Input
2 GND −321 +208 Ground
3 A1 −321 −51 Preamplifier (A1) Output
4 A2 −321 −214 Buffer (A2) Input
5 OUT +321 −388 Buffer (A2) Output
6 VS +322 +363 Supply
7 NC No Connect
8 +IN +322 +561 Noninverting Input

1

2

3

4

8

6

5

08714-003

Figure 3. Metallization Photograph

Rev. A | Page 5 of 16