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High Bandwidth, Bidirectional 65 V Difference Amplifier AD8216
FEATURES
4000 V HBM ESD Ideal for current shunt applications High common-mode voltage range -4 V to +65 V operating -40 V to +80 V survival 3 MHz bandwidth <100 ns output propagation delay Gain: 3 V/V Wide operating temperature range Die: -40C to +150C 8-lead SOIC: -40C to +125C Adjustable output offset Available in 8-lead SOIC Excellent ac and dc performance 10 V/C offset drift 10 ppm/C gain drift
FUNCTIONAL BLOCK DIAGRAM
V+
6
+IN 8
5
OUT
-IN 1
AD8216
7
VREF 1
3
NC 4
2
VREF 2
NC = NO CONNECT
GND
Figure 1.
APPLICATIONS
High-side current sensing in DC-to-dc converters Motor controls Transmission controls Diesel-injection controls Engine management Suspension controls Vehicle dynamic controls
GENERAL DESCRIPTION
The AD8216 is a single-supply, difference amplifier ideal for amplifying small differential voltages in the presence of large common-mode voltages. The operating input common-mode voltage range extends from -4 V to +65 V. The typical supply voltage is 5 V. The AD8216 features a 3 MHz bandwidth, allowing for the input-to-output propagation delay that is always less than 150 ns. This feature is ideal for applications monitoring rapidly increasing and decreasing load currents. The AD8216 is offered in a SOIC package. The operating temperature range is -40C to +125C. Excellent ac and dc performance over temperature keep errors in the measurement loop to a minimum. Offset and gain drift are guaranteed to a maximum of 20 V/C and 15 ppm/C, respectively. The output offset can be adjusted from 0.06 V to 4.9 V with a 5 V supply by using the VREF1 pin and the VREF2 pin. With the VREF1 pin attached to the V+ pin and the VREF2 pin attached to the GND pin, the output is set at half scale. Attaching both VREF1 and VREF2 to GND causes the output to be unipolar, starting near ground. Attaching both VREF1 and VREF2 to V+ causes the output to be unipolar, starting near V+. Other offsets can be obtained by applying an external voltage to VREF1 and VREF2.
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)2007 Analog Devices, Inc. All rights reserved.
07062-001
AD8216 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 Output Offset Adjustment............................................................. 11 Unidirectional Operation.......................................................... 11 Ground Referenced Output ...................................................... 11 V+ Referenced Output .............................................................. 11 Bidirectional Operation............................................................. 11 External ReferenceD Output .................................................... 12 Splitting the Supply .................................................................... 12 Splitting an External Reference ................................................ 12 Applications Information .............................................................. 13 High-Side Current Sense with a Low-Side Switch................. 13 High-Side Current Sense with a High-Side Switch ............... 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 14
REVISION HISTORY
11/07--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
AD8216 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 Conditions Min Typ 3 VOUT 0.1 V dc, 25C Specified temperature range 10 25C Specified temperature range 0.5 10 3 20 0.25 0.4 15 Max Unit V/V % % ppm/C mV mV V/C
400 200 Common mode, continuous Differential, VREF1 and VREF2 tied to GND Differential, VREF1 @ GND and VREF2 @ 5 V 25C, f = dc to 20 kHz 1 Operating temperature range, f = dc to 20 kHz1 RL = 25 k -4 1.6 -800 80 80 0.06 200 3 15 100 20 0.5 Divider to supplies Voltage applied to VREF1 and VREF2 in parallel VS = 5 V 0.499 0.06 0.0 24 4.5 VOUT = 0.1 V dc 70 Operating temperature range -40 +125 1 0.501 0.5 4.9 VS 40 5.5 2 +800 90 90 4.9 +65
Common-Mode Rejection OUTPUT Output Voltage Range Output Resistance DYNAMIC RESPONSE Small Signal -3 dB Bandwidth Slew Rate Propagation Delay NOISE 0.1 Hz to 10 Hz, RTI Spectral Density, 1 kHz, RTI OFFSET ADJUSTMENT Ratiometric Accuracy 2 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
k k V V mV dB dB V MHz V/s ns V p-p V/Hz V/V mV/V V V k V mA dB C
Input-to-output response
150
32
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 16
AD8216 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Supply Voltage Continuous Input Common-Mode Voltage Continuous Input Differential Voltage Reverse Supply Voltage ESD Rating HBM (Human Body Model) CDM (Charged Device Model) Operating Temperature Range Storage Temperature Range Output Short-Circuit Duration Rating 12.5 V -40 V to +80 V 6V 0.3 V 4000 V 1000 V -40C to +125C -65C to +150C Indefinite
ESD CAUTION
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.
Rev. 0 | Page 4 of 16
AD8216 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1 8
-IN 1 GND 2 VREF 2 3
8
+IN VREF 1 V+
07062-003
AD8216
TOP VIEW (Not to Scale)
7 6 5
7 2 6 3 5
07062-002
NC 4
OUT
NC = NO CONNECT
Figure 3. Pin Configuration
Figure 2. Metallization Diagram
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 -320 -357 -349 NC +348 +349 +349 +318 Y +390 +14 -201 NC -325 -194 -26 +390
Die size is 1100 m by 1035 m. Die thickness is 13 mil. Minimum passivation opening (minimum bond pad size) is 92 m x 92 m. Passivation type is 8 kA USG (Oxide) + 10 kA Oxynitride. Bond pad metal composition is 98.5% Al, 1% Si, and 0.5% Cu. Backside potential is V+.
Rev. 0 | Page 5 of 16
AD8216 TYPICAL PERFORMANCE CHARACTERISTICS
500 400 300 200
GAIN (dB)
07062-016
VOSI (V)
100 0 -100 -200 -300 -400 -500 -40 -20 0 20 40 60 80 100 120
10k
100k FREQUENCY (Hz)
1M
TEMPERATURE (C)
Figure 4. Typical Offset Drift
120 110 100 90 80
CMRR (dB)
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
INPUT (200mV/DIV)
70 60 50 40 30 20 10
07062-021
OUTPUT (500mV/DIV)
100
1k
10k
100k
1M
10M
100M
FREQUENCY (Hz)
TIME (200ns/DIV)
Figure 5. CMRR vs. Frequency
1500 1300 1100 900 700
GAIN ERROR (ppm)
Figure 8. Rise Time
500 300 100 -100 -300 -500 -700 -900 -1100 -1300
07062-017
INPUT (200mV/DIV)
OUTPUT (500mV/DIV)
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
TIME (200ns/DIV)
Figure 6. Typical Gain Drift
Figure 9. Fall Time
Rev. 0 | Page 6 of 16
07062-010
-1500 -40
07062-011
0 10
07062-015
20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 1k
AD8216
MAXIMUM OUTPUT SOURCE CURRENT (mA)
10
8
INPUT (1V/DIV)
6
4
OUTPUT (2V/DIV)
2
07062-008
-20
0
20
40
60
80
100
120
140
TIME (500ns/DIV)
TEMPERATURE (C)
Figure 10. Differential Overload Recovery (Falling)
Figure 13. Maximum Output Source Current vs. Temperature
5.0
OUTPUT VOLTAGE RANGE (V)
4.5
INPUT (1V/DIV)
4.0
3.5
3.0
OUTPUT (2V/DIV)
2.5
07062-009
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
TIME (500ns/DIV)
OUTPUT SOURCE CURRENT (mA)
Figure 11. Differential Overload Recovery (Rising)
8 7 6 5 4 3 2 1 0 -40
Figure 14. Output Voltage Range vs. Output Source Current
2.5
OUTPUT VOLTAGE RANGE FROM GND (V)
MAXIMUM OUTPUT SINK CURRENT (mA)
2.0
1.5
1.0
0.5
07062-020
-20
0
20
40
60
80
100
120
140
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
TEMPERATURE (C)
OUTPUT SINK CURRENT (mA)
Figure 12. Maximum Output Sink Current vs. Temperature
Figure 15. Output Voltage Range from GND vs. Output Sink Current
Rev. 0 | Page 7 of 16
07062-006
0
07062-007
2.0
07062-019
0 -40
AD8216
700
BX
TOTAL INPUT BIAS CURRENT (A)
600 500 400 300 200 OUTPUT (50mV/DIV) 100 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 INPUT COMMON-MODE VOLTAGE (V)
AY AX BY ZERO CROSSING PROPAGATION DELAY 85ns
INPUT (50mV/DIV)
07062-014
TIME (50ns/DIV)
Figure 16. Total Input Bias Current vs. Input Common-Mode Voltage
7
Figure 19. Propagation Delay (Falling)
AX
6 5 4 INPUT (50mV/DIV) 3 2 1 OUTPUT (50mV/DIV)
07062-018
07062-012
PROPAGATION DELAY 110ns
OUTPUT ERROR (%)
ZERO CROSSING
0 0.01 0.04 0.07 0.10 0.13 0.16 0.19 0.22 0.25 0.28 0.31 0.34 0.37 1.60 DIFFERENTIAL INPUT (V)
AY
BX
BY
TIME (50ns/DIV)
Figure 17. Output Error (%) vs. Differential Input Voltage (Unidirectional Operation (VREF1 and VREF2 Connected to GND))
1.0 0.8
Figure 20. Propagation Delay (Rising)
TOTAL OUTPUT ERROR (%)
0.6 0.4
8000
0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8
07062-039
COUNT
0.2
6000
4000
2000
07062-037
1.0
0 -15
-10
-5 OFFSET DRIFT (ppm/C)
0
INPUT DIFFERENTIAL VOLTAGE (V)
Figure 18. Output Error (%) vs. Differential Input Voltage (Bidirectional Operation (VREF1 and VREF2 Connected to 2.5 V))
Figure 21. Gain Drift Distribution
Rev. 0 | Page 8 of 16
07062-013
5
AD8216
800 700 600
COUNT
500 400 300 200 100 0 -20
07062-038
-10
0 OFFSET DRIFT (V/C)
10
20
Figure 22. Offset Drift Distribution
Rev. 0 | Page 9 of 16
AD8216 THEORY OF OPERATION
The AD8216 is a single-supply difference amplifier typically used to accurately amplify a small differential current shunt voltage in the presence of a rapidly changing common-mode voltage. The AD8216 consists of an amplifier (A1), a resistor network, a small voltage reference, and a bias circuit (not shown), see Figure 23. The set of input attenuators preceding A1 consist of RA, RB, and RC, which feature a combined series resistance of approximately 200 k 20%. The purpose of these resistors is to attenuate the input voltage to match the input voltage range of A1. This balanced resistor network attenuates the common-mode signal by a ratio of 1/18. 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, which allows the amplifier to operate in the presence of negative common-mode voltages.
B
The reference inputs, VREF1 and VREF2, are tied through resistors to the positive input of A1, 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. When they are used to divide the supply, the gain is 0.5 V/V. The ratios of RA, RB, RC, and RF are trimmed to a high level of precision to allow the CMRR to exceed 80 dB. This performance is accomplished by laser trimming the resistor ratio matching to better than 0.01%.
B
-IN RA
+IN RA A1 VOUT RF
VREF1 RREF
RB
RB
The input resistor network also attenuates normal (differential) mode voltages. Therefore, Amplifier A1 features a gain of 54 V/V to provide a total system gain of 3V/V. Total Gain (V/V) = 1/18 (V/V) x 54 (V/V) = 3 V/V
RC
RC
RREF VREF2
250mV
AD8216
07062-028
GND
Figure 23. Simplified Schematic
Rev. 0 | Page 10 of 16
AD8216 OUTPUT OFFSET ADJUSTMENT
The output of the AD8216 can be adjusted for unidirectional or bidirectional operation.
V+ REFERENCED OUTPUT
The V+ referenced output 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 25).
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8216 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 1.6 V. 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
AD8216
VREF 1
NC GND
VREF 2
GROUND REFERENCED OUTPUT
When using the AD8216 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 24).
Figure 25. V+ Referenced Output
Table 5. V+ = 5 V
VIN (Referred to -IN) 0V -1.6 V VOUT 4.9 V 0.1 V
V+ +IN OUT -IN
BIDIRECTIONAL OPERATION
Bidirectional operation allows the AD8216 to measure currents through a resistive shunt in two directions. 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.
07062-029
AD8216
VREF 1
NC GND NC = NO CONNECT
VREF 2
Table 6. V+ = 5 V, VOUT = 2.5 V with VIN = 0 V
VIN (Referred to -IN) +800 mV -800 mV VOUT 4.9 V 0.1V
Figure 24. Ground Referenced Output
Table 4. V+ = 5 V
VIN (Referred to -IN) 0V 1.6 V VOUT 0.06 V 4.8 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 11 of 16
07062-030
NC = NO CONNECT
AD8216
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 26). 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
AD8216
VREF 1
V+ +IN OUT -IN
NC GND NC = NO CONNECT
VREF 2
07062-032
AD8216
VREF 1
2.5V VOLTAGE REFERENCE
Figure 27. Split Supply
SPLITTING AN EXTERNAL REFERENCE
NC GND NC = NO CONNECT
07062-031
VREF 2
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 28).
Figure 26. External Referenced Output
V+
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 27). The benefit is that no external reference is required to offset the output for bidirectional current measurement. This configuration 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.
+IN OUT -IN
AD8216
VREF 1 5V
VOLTAGE REFERENCE
NC GND NC = NO CONNECT
VREF 2
07062-033
Figure 28. Split External Reference
Rev. 0 | Page 12 of 16
AD8216 APPLICATIONS INFORMATION
A typical application for the AD8216 is high-side measurement of a current through a solenoid for PWM control of the solenoid opening. Typical applications include dc-to-dc converters, motor controls, and solenoid controls. 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 29). An advantage of placing the shunt on the high side is that the entire current, including the recirculation current, can be measured because 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
42V BATTERY
SWITCH +IN VREF 1 V+ SHUNT -IN CLAMP DIODE INDUCTIVE LOAD NC = NO CONNECT
07062-035
OUT
AD8216
GND VREF 2 NC
Figure 30. High-Side Switch
CLAMP DIODE 42V BATTERY SHUNT
Another typical application for the AD8216 is as part of the control loop in H-bridge motor controls. In this case, the AD8216 is placed in the middle of the H-bridge so that it can accurately measure current in both directions by using the shunt available at the motor (see Figure 31). 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 AD8216 measures current in both directions as the H-bridge switches and the motor changes direction. The output of the AD8216 is configured in an external reference bidirectional mode (see the Output Offset Adjustment section).
+IN VREF 1 V+
OUT
AD8216
-IN GND VREF 2 NC
SWITCH
07062-034
CONTROLLER 5V
NC = NO CONNECT
Figure 29. Low-Side Switch
MOTOR +IN VREF 1 V+ OUT
HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH
This configuration minimizes the possibility of unexpected solenoid activation and excessive corrosion (see Figure 30). In this case, both the switch and the shunt are on the high side. When the switch is off, it 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.
AD8216
SHUNT -IN GND VREF 2 NC 5V
2.5V NC = NO CONNECT
07062-036
Figure 31. Motor Control Application
Rev. 0 | Page 13 of 16
AD8216 OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
8
5 4
4.00 (0.1574) 3.80 (0.1497)
1
6.20 (0.2441) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
COMPLIANT TO JEDEC STANDARDS MS-012-A A 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 32. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model AD8216YRZ 1 AD8216YRZ-RL1 AD8216YRZ-R71
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C
Package Description 8-Lead SOIC_N 8-Lead SOIC_N, 13" Tape and Reel 8-Lead SOIC_N, 7" Tape and Reel
012407-A
Package Option R-8 R-8 R-8
Z = RoHS Compliant Part.
Rev. 0 | Page 14 of 16
AD8216 NOTES
Rev. 0 | Page 15 of 16
AD8216 NOTES
(c)2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07062-0-11/07(0)
T T
Rev. 0 | Page 16 of 16

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