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.
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©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
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