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Single-Supply, 42 V System Difference Amplifier AD8206
FEATURES
Ideal for current shunt applications High common-mode voltage range -2 V to +65 V operating -5 V to +68 V survival Gain = 20 Wide operating temperature range Die: -40C to +150C 8-lead SOIC: -40C to +125C Adjustable offset Available in SOIC and die form
FUNCTIONAL BLOCK DIAGRAM
V+
6
+IN 8
5
OUT
-IN 1
AD8206
7
VREF1
3
NC 4
2
VREF2
EXCELLENT AC AND DC PERFORMANCE
15 V/C offset drift 30 ppm/C gain drift 80 dB CMRR dc to 20 kHz
NC = NO CONNECT
GND
Figure 1.
APPLICATIONS
High-side current sensing in Motor controls Transmission controls Diesel-injection controls Engine management Suspension controls Vehicle dynamic controls DC-to-dc converters
GENERAL DESCRIPTION
The AD8206 is a single-supply difference amplifier for amplifying small differential voltages in the presence of large common-mode voltages. The operating input common-mode voltage range extends from -2 V to +65 V. The typical singlesupply voltage is 5 V. The AD8206 is offered in die and packaged form. The operating temperature range for the die is 25C higher (up to 150C) than the packaged part to enable the user to apply the AD8206 in high temperature applications. Excellent DC performance over temperature keeps errors in the measurement loop to a minimum. Offset drift is typically less than 15 V/C, and gain drift is typically below 30 ppm/C. The output offset can be adjusted from 0.08 V to 4.7 V with a 5 V supply by using the VREF1 and VREF2 pins. With VREF1 attached to the V+ pin, and VREF2 attached to the GND pin, the output is set at half scale. Attaching both pins to GND causes the output to be unipolar, starting near ground. Attaching both pins to V+ causes the output to be unipolar starting near V+. Other offsets can be obtained by applying an external voltage to the VREF1 and VREF2 pins.
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.
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) 2005 Analog Devices, Inc. All rights reserved.
04953-001
AD8206 TABLE OF CONTENTS
Features .............................................................................................. 1 Excellent AC and DC Performance................................................ 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 ........................................................................ 8 Output Offset Adjustment............................................................... 9 Unidirectional Operation.............................................................9 Ground Referenced Output .........................................................9 V+ Referenced Output .................................................................9 Bidirectional Operation................................................................9 External ReferenceD Output .................................................... 10 Splitting the Supply .................................................................... 10 Splitting an External Reference ................................................ 10 Applications..................................................................................... 11 High-Side Current Sense with a Low-Side Switch................. 11 High-Side Current Sense with a High-Side Switch ............... 11 Outline Dimensions ....................................................................... 12 Ordering Guide .......................................................................... 12
REVISION HISTORY
7/05--Revision 0: Initial Version
Rev. 0 | Page 2 of 12
AD8206 SPECIFICATIONS
TA = operating temperature range, VS = 5 V, unless otherwise noted. 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 Common Mode Input Voltage Range Common-Mode Rejection Conditions AD8206 SOIC Min Typ Max 20 VO 0.1 V dc, 25C Specified temperature range 30 25C Specified temperature range 15 2 4.5 15 1 1.2 30 2.5 6 Min AD8206 DIE Typ Max 20 1 1.3 Unit V/V % % ppm/C mV mV V/C
400 200 Common mode, continuous Differential 1 25C, f = dc to 20 kHz 2 Operating temperature range, f = dc to 20 kHz2 RL = 25 k -2 76 76 250 86 80 +65 -2 76 76
400 200 +65 250 86 80
k k V mV dB dB
OUTPUT Output Voltage Range Output Resistance DYNAMIC RESPONSE Small Signal -3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, RTI Spectral Density, 1 kHz, RTI OFFSET ADJUSTMENT Ratiometric Accuracy 3 Accuracy, RTO Output Offset Adjustment Range VREF Input Voltage Range VREF Divider Resistor Values POWER SUPPLY Operating Range Quiescent Current Over Temperature Power Supply Rejection Ratio Temperature Range For Specified Performance
1 2 3
0.08 200 100 0.5 20 0.5
4.7
0.08 200 100 0.5 20 0.5
4.7
V kHz V/s V p-p V/Hz
Divider to supplies Voltage applied to VREF1 and VREF2 in parallel VS = 5 V
0.497
0.503 2 4.7 VS 40 5.5 2
0.497
0.503 2 4.7 VS 40 5.5 2
V/V mV/V V V k V mA dB C
0.08 0.0 24 4.5
32
0.08 0.0 24 4.5 70
32
VO = 0.1 V dc 70 Operating temperature range -40
+125
-40
+150
Input voltage range = 125 mV with half-scale offset. Source imbalance <2 . The offset adjustment is ratiometric to the power supply when VREF1 and VREF2 are used as a divider between the supplies.
Rev. 0 | Page 3 of 12
AD8206 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Supply Voltage Continuous Input Voltage Reverse Supply Voltage Operating Temperature Range Storage Temperature Range Output Short-Circuit Duration Rating 12.5 V -5 V to +68 V 0.3 V -40C to +125C -65C to +150C Indefinite
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and 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
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 4 of 12
AD8206 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
-IN 1 GND 2 VREF2 3
8
+IN
NC = NO CONNECT
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic -IN GND VREF2 NC OUT V+ VREF1 +IN X -209 -447 -432 N/A +444 +444 +456 +207 Y +486 +34 -480 N/A -495 -227 +342 +486
Figure 2. Metallization Diagram
04953-002
Die size is 1245 m by 1400 m. Die thickness is 13 mil. Minimum passivation opening (minimum bond pad size) is 92 m x 92 m. Passivation type is 8KA USG (Oxide) + 10KA Oxynitride. Bond pad metal composition is 98.5% Al, 1% Si, and 0.5% Cu. Backside potential is V+.
Rev. 0 | Page 5 of 12
04953-003
VREF1 TOP VIEW 6 V+ (Not to Scale) 5 OUT NC 4
7
AD8206
AD8206 TYPICAL PERFORMANCE CHARACTERISTICS
500 400 300
40 35 30
200
0 -100 -200 -300
04953-036
GAIN (dB)
VOSI (V)
100
TYPICAL IN SOIC
25 20 15 10
04953-007
TYPICAL DIE
-400 -500 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120 140
5 0 10
100
1k 10k FREQUENCY (Hz)
100k
1M
Figure 4. Typical Offset Drift
120 110 100 90 80
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
200mV/DIV
CMR (dB)
70 60 50 40 30 20
04953-004
1V/DIV
04953-023
10 0 10 100 1k 10k 100k FREQUENCY (Hz) 1M
10M
40s/DIV
Figure 5. CMR vs. Frequency
12000 10000 8000 6000 TYPICAL IN SOIC
Figure 8. Rise/Fall Time
250mV/DIV
GAIN ERROR (ppm)
4000 2000 0 -2000 -4000 -6000 -8000
TYPICAL DIE
2V/DIV
-12000 -40
-20
0
20
40 60 80 TEMPERATURE (C)
100
120
140
2s/DIV
Figure 6. Gain Drift
Figure 9. Differential Overload Recovery (Falling)
Rev. 0 | Page 6 of 12
04953-025
-10000
04953-035
AD8206
0.50
MAXIMUM OUTPUT SINK CURRENT (mA)
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120 140
04953-030
250mV/DIV
2V/DIV
04953-024
2s/DIV
Figure 10. Differential Overload Recovery (Rising)
10
Figure 13. Output Sink Current vs. Temperature
MAXIMUM OUTPUT SOURCE CURRENT (mA)
9 8 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120 140
04953-031
2V/DIV
0.01%/DIV
40s/DIV
Figure 11. Settling Time
5.0 4.9 4.8
04953-022
Figure 14. Output Source Current vs. Temperature
OUTPUT VOLTAGE RANGE (V p-p)
50V/DIV
4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.6 3.5 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT SOURCE CURRENT (mA) 3.5 4.0
04953-034
50mV/DIV
3.7
1s/DIV
04953-026
Figure 12. Common-Mode Response
Figure 15. Output Voltage Range vs. Output Source Current
Rev. 0 | Page 7 of 12
AD8206 THEORY OF OPERATION
The AD8206 is a single-supply difference amplifier that uses a unique architecture to accurately amplify small differential current shunt voltages in the presence of rapidly changing common-mode voltage. It is offered in both packaged and die form. In typical applications, the AD8206 is used to measure current by amplifying the voltage across a current shunt placed across the inputs. The gain of the AD8206 is 20 V/V, with an accuracy of 1.2%. This accuracy is guaranteed over the operating temperature range of -40C to +125C. The die temperature range is -40C to +150C with a guaranteed gain accuracy of 1.3%. The input offset is less than 2 mV referred to the input at 25C, and 4.5 mV maximum referred to the input over the full operating temperature range for the packaged part. The die input offset is less than 6 mV referred to the input over the die operating temperature range. The AD8206 operates with a single supply from 4.5 V to 10 V (absolute maximum = 12.5 V). The supply current is less than 2 mA. High accuracy trimming of the internal resistors allows the AD8206 to have a typical common-mode rejection ratio better than 80 dB from dc to 20 kHz. The minimum common-mode rejection ratio over the operating temperature is 76 dB for both the die and packaged part. The output offset can be adjusted from 0.08 V to 4.7 V (VS = 5 V) for unidirectional and bidirectional operation. The AD8206 consists of two amplifiers (A1 and A2), a resistor network, a small voltage reference, and a bias circuit (not shown), see Figure 16. The set of input attenuators preceding A1 consist of RA, RB, and RC, which reduce the common-mode voltage to match the input voltage range of A1. The two attenuators form a balanced bridge network. When the bridge is balanced, the differential voltage created by a common-mode voltage is 0 V at the inputs of A1. The input attenuation ratio is 1/16.7. The combined series resistance of RA, RB, and RC is approximately 200 k 20%. By attenuating the voltages at Pin 1 and Pin 8, the A1 amplifier inputs are held within the power supply range, even if Pin 1 and Pin 8 exceed the supply or fall below common (ground). A reference voltage of 250 mV biases the attenuator above ground. This allows the amplifier to operate in the presence of negative common-mode voltages. The input network also attenuates normal (differential) mode voltages. A1 amplifies the attenuated signal by 26. The input and output of this amplifier are differential to maximize the ac common-mode rejection. A2 converts the differential voltage from A1 into a single-ended signal and provides further amplification. The gain of this second stage is 12.86. The reference inputs, VREF1 and VREF2, are tied through resistors to the positive input of A2, which allows the output offset to be adjusted anywhere in the output operating range. The gain is 1 V/V from the reference pins to the output when the reference pins are used in parallel. The gain is 0.5 V/V when they are used to divide the supply. The ratios of Resistors RA, RB, RC, RD, and RF are trimmed to a high level of precision to allow the common-mode rejection ratio to exceed 80 dB. This is accomplished by laser trimming the resistor ratio matching to better than 0.01%. The total gain of 20 is made up of the input attenuation of 1/16.7 multiplied by the first stage gain of 26 and the second stage gain of 12.86. The output stage is a Class A with a PNP pull-up transistor and a 300 A current sink pull-down.
-IN RA +IN RA A1 RB RB RF RF RD RD
RC
RC
A2 RE RF
VOUT VREF1 RREF RREF
04953-013
250mV
AD8206
GND
VREF2
Figure 16. Simplified Schematic
Rev. 0 | Page 8 of 12
AD8206 OUTPUT OFFSET ADJUSTMENT
The output of the AD8206 can be adjusted for unidirectional or bidirectional operation.
V+ REFERENCED OUTPUT
This mode is set when both reference pins are tied to the positive supply. It is typically used when the diagnostic scheme requires detection of the amplifier and the wiring before power is applied to the load (see Figure 18).
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8206 to measure currents through a resistive shunt in one direction. The basic modes for unidirectional operation are ground referenced output mode and V+ referenced output mode. For unidirectional operation, the output can be set at the negative rail (near ground) or at the positive rail (near V+) when the differential input is 0 V. The output moves to the opposite rail when a correct polarity differential input voltage is applied. In this case, full scale is approximately 250 mV. The required polarity of the differential input depends on the output voltage setting. If the output is set at the positive rail, the input polarity needs to be negative to move the output down. If the output is set at ground, the polarity is positive to move the output up.
V+ +IN OUT -IN
AD8206
VREF1
NC GND NC = NO CONNECT
VREF2
04953-015
GROUND REFERENCED OUTPUT
When using the AD8206 in this mode, both referenced inputs are tied to ground, which causes the output to sit at the negative rail when there are zero differential volts at the input (see Figure 17). Table 5. V+= 5 V
Figure 18. V+ Referenced Output
VIN (Referred to -IN) 0V -250 mV
VO 4.7 V 0.08 V
V+ +IN OUT -IN
BIDIRECTIONAL OPERATION
Bidirectional operation allows the AD8206 to measure currents through a resistive shunt in two directions.
AD8206
VREF1
NC GND NC = NO CONNECT
VREF2
04953-014
In this case, the output is set anywhere within the output range. Typically, it is set at half-scale for equal range in both directions. In some cases, however, it is set at a voltage other than half-scale when the bidirectional current is nonsymmetrical. Table 6. V+ = 5 V, VO = 2.5 V with VIN = 0 V
VIN (Referred to -IN) +100 mV -100 mV VO 4.5 V 0.5 V
Figure 17. Ground Referenced Output
Table 4. V+ = 5 V
VIN (Referred to -IN) 0V 250 mV VO 0.08 V 4.7 V
Adjusting the output is accomplished by applying voltage(s) to the referenced inputs. VREF1 and VREF2 are tied to internal resistors that connect to an internal offset node. There is no operational difference between the pins.
Rev. 0 | Page 9 of 12
AD8206
EXTERNAL REFERENCED OUTPUT
Tying both pins together and to a reference produces an output equal to the reference voltage when there is no differential input (see Figure 19). The output moves down from the reference voltage when the input is negative, relative to the -IN pin and up when the input is positive, relative to the -IN pin.
V+ +IN OUT -IN
AD8206
V+ +IN OUT -IN
VREF1
NC GND
VREF1
VREF2
04953-017
NC = NO CONNECT
2.5V VOLTAGE REFERENCE
AD8206
Figure 20. Split Supply
NC GND NC = NO CONNECT
04953-016
VREF2
SPLITTING AN EXTERNAL REFERENCE
In this case, an external reference is divided by 2 with an accuracy of approximately 0.5% by connecting one VREF pin to ground and the other VREF pin to the reference (see Figure 21).
Figure 19. External Referenced Output
SPLITTING THE SUPPLY
By tying one reference pin to V+ and the other to the ground pin, the output is set at half of the supply when there is no differential input (see Figure 20). The benefit is that no external reference is required to offset the output for bidirectional current measurement. This creates a midscale offset that is ratiometric to the supply, which means that if the supply increases or decreases, the output remains at half the supply. For example, if the supply is 5.0 V, the output is at half scale or 2.5 V. If the supply increases by 10% (to 5.5 V), the output goes to 2.75 V.
V+ +IN OUT -IN
AD8206
VREF1 5V
VOLTAGE REFERENCE
NC GND NC = NO CONNECT
VREF2
04953-018
Figure 21. Split External Reference
Rev. 0 | Page 10 of 12
AD8206 APPLICATIONS
A typical application for the AD8206 is high-side measurement of a current through a solenoid for PWM control of the solenoid opening. Typical applications include hydraulic transmission control and diesel injection control. Two typical circuit configurations are used for this type of application. When using a high-side switch, the battery voltage is connected to the load when the switch is closed, causing the commonmode voltage to increase to the battery voltage. In this case, when the switch is opened, the voltage reversal across the inductive load causes the common-mode voltage to be held one diode drop below ground by the clamp diode.
5V
HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH
In this case, the PWM control switch is ground referenced. An inductive load (solenoid) is tied to a power supply. A resistive shunt is placed between the switch and the load (see Figure 22). An advantage of placing the shunt on the high side is that the entire current, including the recirculation current, can be measured since the shunt remains in the loop when the switch is off. In addition, diagnostics can be enhanced because shorts to ground can be detected with the shunt on the high side. In this circuit configuration, when the switch is closed, the common-mode voltage moves down to near the negative rail. When the switch is opened, the voltage reversal across the inductive load causes the common-mode voltage to be held one diode drop above the battery by the clamp diode.
5V INDUCTIVE LOAD
SWITCH 42V BATTERY SHUNT -IN CLAMP DIODE INDUCTIVE LOAD NC = NO CONNECT
04953-020
+IN VREF1 +VS
OUT
AD8206
GND VREF2 NC
Figure 23. High-Side Switch
CLAMP DIODE 42V BATTERY SHUNT
+IN VREF1 +VS
OUT
Another typical application for the AD8206 is as part of the control loop in H-bridge motor control. In this case, the AD8206 is placed in the middle of the H-bridge (see Figure 24) so that it can accurately measure current in both directions by using the shunt available at the motor. This is a better solution than a ground referenced op amp because ground is not typically a stable reference voltage in this type of application. This instability in the ground reference causes the measurements that could be made with a simple ground referenced op amp to be inaccurate. The AD8206 measures current in both directions as the H-bridge switches and the motor changes direction. The output of the AD8206 is configured in an external reference bidirectional mode, see the Output Offset Adjustment section.
AD8206
-IN GND VREF2 NC
SWITCH
04953-019
NC = NO CONNECT
CONTROLLER 5V
Figure 22. Low-Side Switch
HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH
This configuration minimizes the possibility of unexpected solenoid activation and excessive corrosion (see Figure 23). In this case, both the switch and the shunt are on the high side. When the switch is off, this removes the battery from the load, which prevents damage from potential shorts to ground, while still allowing the recirculating current to be measured and providing for diagnostics. Removing the power supply from the load for the majority of the time minimizes the corrosive effects that could be caused by the differential voltage between the load and ground.
MOTOR
+IN VREF1 +VS
OUT
AD8206
SHUNT -IN GND VREF2 NC 5V
NC = NO CONNECT
Figure 24. Motor Control Application
Rev. 0 | Page 11 of 12
04953-021
2.5V
AD8206 OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
8 5 4
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440) 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-012AA 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 25. 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model AD8206YRZ 1 AD8206YRZ-REEL1 AD8206YRZ-REEL71 AD8206YCSURF
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +150C
Package Description 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel Die Form
Package Option R-8 R-8 R-8
Z = Pb-free part.
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04953-0-7/05(0)
Rev. 0 | Page 12 of 12

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