ANALOG DEVICES AD8212 Service Manual
High Voltage
V
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FEATURES
Adjustable gain
High common-mode voltage range
7 V to 65 V typical
7 V to >500 V with external pass transistor
Current output
Integrated 5 V series regulator
8-lead MSOP package
Operating temperature range of −40°C to +125°C
APPLICATIONS
Current shunt measurement
Motor controls
DC-to-DC converters
Power supplies
Battery monitoring
Remote sensing
Current Shunt Monitor
AD8212
FUNCTIONAL BLOCK DIAGRAM
V+
1
AD8212
BIAS
CIRCUIT
COM BIAS ALPHA
I
OUT
Figure 1.
SENSE
8
OUTPUT
CURRENT
COMPENSATI ON
6325
05942-001
GENERAL DESCRIPTION
The AD8212 is a high common-mode voltage, current shunt
monitor. It accurately amplifies a small differential input voltage
in the presence of large common-mode voltages up to 65 V
(>500 V with an external PNP transistor).
The AD8212 is ideal for current monitoring across a shunt
r
esistor in applications controlling loads, such as motors and
solenoids. The current output of the device is proportional to
the input differential voltage. The user can select an external
resistor to set the desired gain. The typical common-mode
voltage range of the AD8212 is 7 V to 65 V.
Another feature of the AD8212 is high voltage operation,
ich is achieved by using an external high voltage breakdown
wh
PNP transistor. In this configuration, the common-mode range
of the AD8212 is equal to the breakdown of the external PNP
transistor. Therefore, operation at several hundred volts is easily
achieved (see
Figure 23).
The AD8212 features a patented output base current compensat
ion circuit for high voltage operation mode. This ensures that
no base current is lost through the external transistor and
excellent output accuracy is maintained regardless of commonmode voltage or temperature.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2007 Analog Devices, Inc. All rights reserved.
AD8212
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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 ........................................................................ 9
REVISION HISTORY
11/07—Rev. 0 to Rev. A
Increased Operating Temperature Range........................Universal
5/07—Revision 0: Initial Version
Normal Operation (7 V to 65 V Supply (V+) Range)..............9
High Voltage Operation Using an External PNP Transistor 10
Output Current Compensation Circuit................................... 10
Applications Information.............................................................. 11
General High-Side Current Sensing........................................ 11
Motor Control............................................................................. 11
500 V Current Monitor ............................................................. 11
Bidirectional Current Sensing.................................................. 12
Outline Dimensions....................................................................... 13
Ordering Guide .......................................................................... 13
Rev. A | Page 2 of 16
AD8212
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SPECIFICATIONS
VS = 15 V, T
Table 1.
Parameter Conditions/Comments Min Typ Max Unit
SUPPLY VOLTAGE (V+) No external pass transistor 7 65 V
With external PNP transistor
SUPPLY CURRENT2 (I
V+ = 7 V to 65 V 220 720 μA
High voltage operation, using external PNP 200 1500 μA
VOLTAGE OFFSET
Offset Voltage (RTI) TA ±2 mV
Over Temperature (RTI) T
Offset Drift T
INPUT
Input Impedance
Differential 2 kΩ
Common Mode (VCM) V+ = 7 V to 65 V 5 MΩ
Voltage Range
Differential Maximum voltage between V+ and V
V
SENSE
OUTPUT
Transconductance 1000 μA/V
Current Range (I
Gain Error for T
Impedance 20 MΩ
Voltage Range 0 V+ − 5 V
REGULATOR
Nominal Value 7 V ≤ V+ ≤ 65 V 4.80 5 5.20 V
PSRR 7 V ≤ V+ ≤ 65 V 80 dB
Bias Current (I
T
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth Gain = 10 1000 kHz
Gain = 20 500 kHz
Gain = 50 100 kHz
Settling Time Within 0.1% of the true output, gain = 20 2 μs
ALPHA PIN INPUT CURRENT 25 μA
NOISE
0.1 Hz to 10 Hz, RTI 1.1 μV p-p
Spectral Density, 1 kHz, RTI 40
TEMPERATURE RANGE
For Specified Performance (T
1
Range dependent on the VCE breakdown of the transistor.
2
The AD8212 supply current in normal voltage operation (V+ = 7 V to 65 V) is the bias current (I
differential voltage and can range from 0 μA to 500 μA. I
to the High Voltage Operation Using an External PNP Transistor section.
3
The current of the amplifier into V
for more information.
= −40°C to +125°C, TA = 25°C, unless otherwise noted.
OPR
= I
+ I
OUT
, 7 V ≤ V+ ≤ 65 V 185 200 μA
, high voltage operation 200 1000 μA
in this mode of operation is typically 185 μA and 200 μA maximum. For high voltage operation mode, refer
BIAS
(Pin 8) Current
OUT
7 V ≤ V+ ≤ 65 V, with respect to 500 μA full scale ±1 %
OPR
) T
BIAS
SUPPLY
OPR
OPR
3
V+ = 7 V to 65 V, T
) 7 V ≤ V+ ≤ 65 V, 0 mV to 500 mV differential input 500 μA
OPR
OPR
) −40 +125 °C
OPR
(Pin 8) increases when operating in high voltage mode. See the High Voltage Operation Using an External PNP Transistor section
SENSE
1
)
BIAS
7 >500 V
±3 mV
±10 μV/°C
SENSE
100 200 nA
OPR
500 mV
nV/√Hz
) added to output current (I
BIAS
). Output current varies upon input
OUT
Rev. A | Page 3 of 16
AD8212
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ABSOLUTE MAXIMUM RATINGS
T
= −40°C to +125°C, unless otherwise noted.
OPR
Table 2.
Parameter Rating
Supply Voltage 65 V
Continuous Input Voltage 68 V
Reverse Supply Voltage 0.3 V
Operating Temperature Range −40°C to +125°C
Storage Temperature Range −40°C to +150°C
Output Short-Circuit Duration Indefinite
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
AD8212
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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
V+ 1
AD8212
2
COM
3
BIAS
TOP VIEW
(Not to Scale)
NC 4
NC = NO CONNECT
Figure 2. Pin Configuration
8
7
6
5
V
SENSE
NC
ALPHA
I
OUT
1
2
3
05942-002
Figure 3. Metallization Diagram
Table 3. Pin Function Descriptions
Pin No. Mnemonic X Coordinate Y Coordinate Description
1 V+ −393 +219 Supply Voltage (Inverting Amplifier Input).
2 COM −392 +67 Regulator Low Side.
3 BIAS −392 −145
4 NC – –
5 I
+386 −82 Output Current.
OUT
6 ALPHA +386 +23
7 NC +386 +118
8 V
+386 +210 Noninverting Amplifier Input.
SENSE
Bias Circuit Low Side.
No Connect.
Current Compensation Circuit Input.
No Connect.
8
6
5
05942-025
Rev. A | Page 5 of 16
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