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Preliminary Technical Data
FEATURES
High common-mode voltage range 7 V to +65 V operating (no outside pass transistor) 7 V to >500 V survival (with outside pass transistor) Adjustable gain Bidirectional current measurement Wide operating temperature range Die: -40C to +150C 8-lead SOIC: -40C to +125C Available in SOIC and die form
VPLUS -
High Voltage Current Shunt Monitor AD8212
FUNCTIONAL BLOCK DIAGRAM
IS RS +IN -IN LOAD +
AD8212
OFFSET 99k
APPLICATIONS
High-side current sensing Motor controls Battery monitoring Hybrid vehicle control Diesel injection controls Vehicle dynamic controls Dc-to-dc converters
IOUT
ALPHA
COM
BIAS
RBIAS
ROUT
Figure 1.
GENERAL DESCRIPTION
The AD8212 is a self-biased current sense amplifier for level shifting and amplifying small differential voltages in the presence of common mode voltages exceeding 500 V1. The AD8212 offers excellent accuracy and programmable gain which can be set with a single resistor, making it ideal to use in industrial, automotive , and consumer applications. The AD8212 is offered in die and packaged form. The operating temperature range for the die is 25C higher (up to 150C) than that of the packaged part to enable the user to apply the AD8212 in high temperature applications. Excellent AC and DC performance over temperature keep errors in the measurement loop to a minimum. Offset drift is typically below 5 uV/ C, and the gain drift is typically below 50 ppm/C.
1
Depending upon Vce breakdown voltage of pass transistor Rev. PrA
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.
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 (c)2006 Analog Devices, Inc. All rights reserved.
05492-001
AD8212 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Pin Configuration......................................................................... 4
Preliminary Technical Data
Theory of Operation .........................................................................5 Modes of Operation ..........................................................................6 Low Voltage Unidirectional Operation ......................................6 Low Voltage BIidirectional Operation .......................................6 High Voltage Unidirectional Operation.....................................6 High Voltage Bidirectional Operation........................................6 Outline Dimensions ..........................................................................7
Rev. PrA | Page 2 of 8
Preliminary Technical Data SPECIFICATIONS
TA = Operating temperature range. Table 1.
Parameter GAIN Initial Accuracy Accuracy Over Temperature Gain vs. Temperature VOLTAGE OFFSET Offset Voltage (RTI) Over Temperature (RTI) Offset Drift INPUT Input Impedance Differential Input Voltage Range Differential Input Range3 Common-Mode Rejection OUTPUT Output Voltage Range DYNAMIC RESPONSE Small Signal - 3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, RTI Spectral Density, 1 kHz, RTI
1 2 3
AD8212
AD8212 SOIC1 Min Typ Max 1 0.5 50 1 2 5 100 1 1.5
Min 1
AD8212 DIE2 Typ Max 100 1.5 2.5
Unit V/V % % ppm/C mV mV V/C
Conditions
0.5 50
25C, VO 0.1 V dc Specified temperature range
2 4 5
25C Specified temperature range
2 7 7 100 90 0.05 500 3 TBD TBD VPLUS - 5 V 0.05 65 >500 7 7
2 65 >500 100 90 VPLUS - 5 V 500 3 TBD TBD
k V V mV dB V kHz V/s V p-p V/Hz
No outside pass transistor With outside pass transistor Differential 25C, f = dc to 20 kHz4 RL = 25 k
TMIN to TMAX = -40C to +125C. TMIN to TMAX = -40C to +150C. Input voltage range = 75 mV with half-scale offset. 4 Source imbalance <2 .
Rev. PrA | Page 3 of 8
AD8212 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Continuous Input Voltage Transient Input Voltage Operating Temperature Range Storage Temperature Range Rating 7V to +65 V (No Pass Transistor) 72 V -40C to +125C -65C to +150C
Preliminary Technical Data
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
PIN CONFIGURATION
VPLUS 1 COM 2 BIAS 3
8
AD8212
VSENSE OFFSET
7
NC = NO CONNECT
Figure 2. Pin Configuration
Rev. PrA | Page 4 of 8
05492-002
6 ALPHA TOP VIEW NC 4 (Not to Scale) 5 IOUT
Preliminary Technical Data THEORY OF OPERATION
The AD8212 is a self-biased, high common mode current sense amplifier.
VPLUS IS RS +IN RG1 -IN LOAD
+IN RS -IN
AD82122
between the Vplus and COM. Therefore, the device always sees 5 V across, no matter what the common mode voltage. The AD8212 can operate with voltages of up to 500V with the use of an external pass transistor.
VPLUS IS
AD8212
OFFSET 99k
OFFSET
LOAD
AD8212
Q1
IOUT
VOUT
Q1
99k
BIAS
IOUT
05492-003
COM
ALPHA
ROUT
BIAS
Figure 3. Typical Connection Diagram
COM
ALPHA ROUT RBIAS
VOUT
The current (IS) is drawn for the supply through the shunt resistor (RS). This produces a small voltage (Vshunt) across the inputs of the device, and in turn current flows across RG1 (1000 ) into the collector of Q1. This current (IOUT) is converted into a voltage through the use of an outside resistor (ROUT). RG1 = 1000 Iout = (Is * Rs) / (RG1) Vshunt = (Is * Rs) Vout = (Is * Rs * Rout) / RG1
Figure 4.
At these high voltages a proper Rbias (depended upon the application) is necessary to regulate the device by pulling enough current through it to keep it to keep it going.
Ibias = (Vsupply -5V)/ Rbias
Table 3 lists the Rout values and the resulting gain for the AD8212. Table 3.
Rout () 1k 2k 5k 10k 20k 50k 100k Gain (V/V) 1 2 5 10 20 50 100
The current necessary must be at least 90uA and can be as high as 1mA. The formula above can be used to easily calculate the external Rbias to deliver the proper current.
The Offset pin can be tied to COM for bidirectional current measurements. The Offset voltage can be calculated by: Voffset = (5 * 10^-5) * Rout Between Vplus and COM there is 5V. When Offset is tied to Com we have a resistor divider of 1K and 99K and 5V. Therefore the current flowing to the Q1 collector is 0.5V/1k=(5*10^-5). This current multiplied with Rout produces the offset voltage. A high voltage PNP transistor is necessary for using the AD8212 at high voltages. The only limitation on what Common Mode Voltage range, is the breakdown voltage of the pass transistor.
With the device operating in the manner shown above the common mode voltage range is 7V to 65V. The 7V is necessary for the device to operate because of an internal regulator that turns on at that voltage. This internal regulator allows the AD8212 to be self biased, meaning that the AD8212 hangs from the common mode voltage, and no additional supply is necessary. This internal regulator also maintains 5 V at all times
Rev. PrA | Page 5 of 8
05492-004
Preliminary Technical Data MODES OF OPERATION
The output of the AD8212 can be adjusted for unidirectional or bidirectional operation.
AD82122
HIGH VOLTAGE UNIDIRECTIONAL OPERATION
VPLUS IS RS LOAD
1 2 3 4
LOW VOLTAGE UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8212 to measure currents through a resistive shunt in one direction. The offset pin is not used and the Bias pin is directly connected to GND.
VPLUS IS RS LOAD
1 2 3 4
VPLUS COM BIAS NC
VSENSE
8
OFFSET 7 ALPHA 6 IOUT 5 ROUT
05492-007
AD8212
RBIAS
VPLUS COM BIAS NC
VSENSE
8
OFFSET 7 ALPHA 6 IOUT 5 ROUT
05492-005
Figure 7. High Voltage Unidirectional Operation
AD8212
HIGH VOLTAGE BIDIRECTIONAL OPERATION
VPLUS IS RS LOAD
1
Figure 5. Low Voltage Unidirectional Operation
VPLUS COM BIAS NC
VSENSE
8
LOW VOLTAGE BIIDIRECTIONAL OPERATION
By tying pin 7 (Offset) to COM the AD8212 can measure currents in both directions at the input.
VPLUS IS RS LOAD
1 2 3 4
2 3 4
OFFSET 7 ALPHA 6 IOUT 5 ROUT
AD8212
RBIAS
VSENSE
VPLUS COM BIAS NC
8
Figure 8.. High Voltage Unidirectional Operation
OFFSET 7 ALPHA
6
AD8212
IOUT 5 ROUT
05492-006
Figure 6. Low Voltage Bidirectional Operation
Rev. PrA | Page 6 of 8
05492-008
Preliminary Technical Data OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
8 5
AD82122
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440)
4 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040)
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) x 45 0.25 (0.0099)
0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 9. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches
Rev. PrA | Page 7 of 8
AD8212 NOTES
Preliminary Technical Data
(c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05492-0-9/06(PrA)
Rev. PrA | Page 8 of 8

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