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High Voltage Current Shunt Monitor AD8211
FEATURES
4000 V HBM ESD High common-mode voltage range -2 V to +65 V operating -3 V to +68 V survival Buffered output voltage Wide operating temperature range 5-lead SOT: -40C to +125C Excellent ac and dc performance 5 V/C typical offset drift -13 ppm/C typical gain drift 120 dB typical CMRR at dc
FUNCTIONAL BLOCK DIAGRAM
VIN+ VIN-
A1 PROPRIETARY OFFSET CIRCUITRY
V+
OUT G = +20
APPLICATIONS
High-side current sensing Motor controls Transmission controls Engine management Suspension controls Vehicle dynamic controls DC-to-dc converters
GND
Figure 1.
GENERAL DESCRIPTION
The AD8211 is a high voltage, precision current shunt amplifier. It features a set gain of 20 V/V, with a typical 0.5% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. Excellent commonmode rejection from -2 V to +65 V is independent of the 5 V supply. The AD8211 performs unidirectional current measurements across a shunt resistor in a variety of industrial and automotive applications, such as motor control, solenoid control, or battery management. Special circuitry is devoted to output linearity being maintained throughout the input differential voltage range of 0 mV to 250 mV, regardless of the common-mode voltage present. The AD8211 has an operating temperature range of -40C to +125C and is offered in a small 5-lead SOT package.
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.
06824-001
AD8211
AD8211 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 Application Notes ........................................................................... 11 Output Linearity......................................................................... 11 Applications Information .............................................................. 12 High-Side Current Sense with a Low-Side Switch................. 12 High-Side Current Sensing ....................................................... 12 Low-Side Current Sensing ........................................................ 12 Outline Dimensions ....................................................................... 13 Ordering Guide .......................................................................... 13
REVISION HISTORY
7/07--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
AD8211 SPECIFICATIONS
TOPR = -40C to +125C, TA = 25C, VS = 5 V, RL = 25 k (RL is the output load resistor), 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 Common-Mode Input Voltage Range Differential Input Voltage Range Common-Mode Rejection OUTPUT Output Voltage Range Low Output Voltage Range High Output Impedance DYNAMIC RESPONSE Small Signal -3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, RTI Spectral Density, 1 kHz, RTI POWER SUPPLY Operating Range Quiescent Current Over Temperature Power Supply Rejection Ratio TEMPERATURE RANGE For Specified Performance
1 2
Min
Typ 20
Max
Unit V/V % % ppm/C mV mV V/C
Conditions
0.25 0.35 -13 1 2.2 5
VO 0.1 V dc TOPR TOPR 1 25C TOPR TOPR 2
5 5 3.5 -2 100 80 0.1 250 120 90 0.05 4.95 2 500 4.5 7 70 4.5 1.2 76 -40 +125 5.5 2.0 +65
k M k V mV dB dB V V kHz V/s V p-p nV/Hz V mA dB C
Common-mode voltage > 5 V Common-mode voltage < 5 V Common-mode continuous Differential input voltage TA, f = dc, VCM > 5 V, see Figure 5 TA, f = dc, VCM < 5 V, see Figure 5
4.9
VCM > 5 V 3 , see Figure 12
The mean of the gain drift distribution is typically -13 ppm/C, with a = 3 ppm/C. The mean of the offset drift distribution is typically +5 V/C, with a = 3 V/C. 3 When the input common-mode voltage is less than 5 V, the supply current increases, which can be calculated by IS = -0.275 (VCM) + 2.5.
Rev. 0 | Page 3 of 16
AD8211 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Supply Voltage Continuous Input Voltage Reverse Supply Voltage HBM (Human Body Model) ESD Rating CDM (Charged Device Model) ESD Rating Operating Temperature Range Storage Temperature Range Output Short-Circuit Duration Rating 12.5 V -3 V to +68 V -0.3 V 4000 V 1000 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; 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. 0 | Page 4 of 16
AD8211 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
OUT 1
5
V+
AD8211
1
2
5
GND 2 VIN+ 3
TOP VIEW (Not to Scale)
06824-002
4
VIN-
NC = NO CONNECT
Figure 3. Pin Configuration
Figure 2. Metallization Diagram
Table 3. Pin Function Descriptions
Pin No. 1 2 3 4 5 Mnemonic OUT GND VIN+ VIN- V+ X -277 -140 -228 +229 +264 Y +466 +466 -519 -519 +466 Description Buffered Output. Ground. Noninverting Input. Inverting Input. Supply.
06824-030
3
4
Rev. 0 | Page 5 of 16
AD8211 TYPICAL PERFORMANCE CHARACTERISTICS
1.2 1.0 0.8 0.6 0.4 40 35 30 25 20 15
VOSI (mV)
0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -40 -20 0 20 40 60 80 100 120
06824-112
GAIN (dB)
10 5 0 -5 -10 -15 -20
06824-107
-25 -30 -35 -40 10k
100k FREQUENCY (Hz)
1M
10M
TEMPERATURE (C)
Figure 4. Typical Offset vs. Temperature
140 130 COMMON-MODE VOLTAGE > 5V 120 110 100 COMMON-MODE VOLTAGE < 5V 90 80
06824-114
Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p)
10 9
TOTAL OUTPUT ERROR (%)
8 7 6 5 4 3 2 1 0 DIFFERENTIAL INPUT VOLTAGE (mV)
06824-118
CMRR (dB)
70 60 10
100
1k
10k
100k
1M
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 250
FREQUNCY (Hz)
Figure 5. Typical CMRR vs. Frequency
2500 2000 1500
Figure 8. Total Output Error vs. Differential Input Voltage
-510 -515 -520
INPUT BIAS CURRENT (A)
-525 -530 -535 -540 -545 -550 -555 -560
06824-103
GAIN ERROR (PPM)
1000 500 0 -500 -1000 -1500 -2000 -2500 -40
06824-113
VIN+
VIN-
-565 -570 0 25 50 75 100 125 150 175 200 225 DIFFERENTIAL INPUT VOLTAGE (mV)
-20
0
20
40
60
80
100
120
250
TEMPERATURE (C)
Figure 6. Typical Gain Error vs. Temperature
Figure 9. Input Bias Current vs. Differential Input Voltage, VCM = 0 V
Rev. 0 | Page 6 of 16
AD8211
110 100
INPUT BIAS CURRENT (A)
100mV/DIV
90 VIN+ 80
INPUT 1V/DIV
70 VIN-
60
OUTPUT
06824-104
50 40 0 25 50 75 100 125 150 175 200 225 DIFFERENTIAL INPUT VOLTAGE (mV)
250
TIME (500ns/DIV)
Figure 10. Input Bias Current vs. Differential Input Voltage, VCM = 5 V
0.8 0.4
Figure 13. Fall Time
INPUT BIAS CURRENT (mA)
0 -0.4 -0.8 -1.2 -1.6
06824-102
INPUT 100mV/DIV OUTPUT
1V/DIV
-2.0 -2.4 -5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
INPUT COMMON-MODE VOLTAGE (V)
TIME (500ns/DIV)
Figure 11. Input Bias Current vs. Input Common-Mode Voltage
4.0
Figure 14. Rise Time
200mV/DIV
3.5
SUPPLY CURRENT (mA)
3.0
INPUT
2.5
2V/DIV
2.0
1.5
06824-101
OUTPUT
06824-109
1.0 -4
-2
0
2
4
6
8
65
COMMON-MODE VOLTAGE (V)
TIME (1s/DIV)
Figure 12. Supply Current vs. Common-Mode Voltage
Figure 15. Differential Overload Recovery (Falling)
Rev. 0 | Page 7 of 16
06824-111
06824-110
AD8211
12.0
INPUT
MAXIMUM OUTPUT SINK CURRENT (mA)
11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5
06824-106
200mV/DIV
OUTPUT
2V/DIV
06824-108
6.0 5.5 5.0
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
TIME (1s/DIV)
TEMPERATURE (C)
Figure 16. Differential Overload Recovery (Rising)
Figure 19. Maximum Output Sink Current vs. Temperature
9.0
MAXIMUM OUTPUT SOURCE CURRENT (mA)
2V/DIV
8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 -40 -20 0 20 40 60 80 100 120 140
06824-105
0.01/DIV
TIME 5s/DIV)
06824-120
TEMPERATURE (C)
Figure 17. Settling Time (Falling)
Figure 20. Maximum Output Source Current vs. Temperature
5.0 4.6
2V/DIV
OUTPUT VOLTAGE RANGE (V)
06824-119
4.2 3.8 3.4 3.0 2.6 2.2 1.8 1.4 1.0 0 1 2 3 4 5 6 7 8 9 OUTPUT SOURCE CURRENT (mA)
06824-117
0.01/DIV
TIME 5s/DIV)
Figure 18. Settling Time (Rising)
Figure 21. Output Voltage Range vs. Output Source Current
Rev. 0 | Page 8 of 16
AD8211
2.0
OUTPUT VOLTAGE RANGE FROM GND (V)
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 6 7 8 9 10 11 12 OUTPUT SINK CURRENT (mA)
06824-116
Figure 22. Output Voltage Range from GND vs. Output Sink Current
Rev. 0 | Page 9 of 16
AD8211 THEORY OF OPERATION
In typical applications, the AD8211 amplifies a small differential input voltage generated by the load current flowing through a shunt resistor. The AD8211 rejects high common-mode voltages (up to 65 V) and provides a ground-referenced, buffered output that interfaces with an analog-to-digital converter (ADC). Figure 23 shows a simplified schematic of the AD8211.
ISHUNT RSHUNT IIN R1 R
A load current flowing through the external shunt resistor produces a voltage at the input terminals of the AD8211. The input terminals are connected to Amplifier A1 by Resistor R and Resistor R1. The inverting terminal, which has very high input impedance is held to (VCM) - (ISHUNT x RSHUNT) because negligible current flows through Resistor R. Amplifier A1 forces the noninverting input to the same potential. Therefore, the current that flows through Resistor R1, is equal to IIN = (ISHUNT x RSHUNT)/R1 This current (IIN) is converted back to a voltage via ROUT. The output buffer amplifier has a gain of 20 V/V and offers excellent accuracy as the internal gain setting resistors are precision trimmed to within 0.01% matching. The resulting output voltage is equal to VOUT = (ISHUNT x RSHUNT) x 20
A1 PROPRIETARY OFFSET CIRCUITRY Q1
V+
VOUT = (ISHUNT x RSHUNT ) x 20 ROUT G = +20
GND
Figure 23. Simplified Schematic
06824-022
AD8211
Rev. 0 | Page 10 of 16
AD8211 APPLICATION NOTES
OUTPUT LINEARITY
In all current sensing applications, and especially in automotive and industrial environments where the common-mode voltage can vary significantly, it is important that the current sensor maintain the specified output linearity, regardless of the input differential or common-mode voltage. The AD8211 contains specific circuitry on the input stage, which ensures that even when the differential input voltage is very small, and the common-mode voltage is also low (below the 5 V supply), the input-to-output linearity is maintained. Figure 24 shows the input differential voltage vs. the corresponding output voltage at different common modes.
200 180 160
Regardless of the common mode, the AD8211 provides a correct output voltage when the input differential is at least 2 mV, which is due to the voltage range of the output amplifier that can go as low as 33 mV typical. The specified minimum output amplifier voltage is 100 mV to provide sufficient guardbands. The ability of the AD8211 to work with very small differential inputs, regardless of the common-mode voltage, allows for more dynamic range, accuracy, and flexibility in any current sensing application.
OUTPUT VOLTAGE (mV)
140 120 100 80 60 40 20 0 0 1 2 3 4 5 6 7 8 9 10 DIFFERENTIAL INPUT VOLTAGE (mV) IDEAL VOUT (mV) VOUT (mV) @ VCM = 0V VOUT (mV) @ VCM = 65V
Figure 24. Gain Linearity Due to Differential and Common-Mode Voltage
06824-115
Rev. 0 | Page 11 of 16
AD8211 APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH
In such load control configurations, the PWM-controlled 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 25). 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.
1 3 2 1 3
OVERCURRENT DETECTION (<100ns)
5 6 7 8
OUT
GND
NC
-IN
AD8214
NC
4
VREG
3
+IN
2
VS
1
1 3
2
1 3
OUT
GND
VIN+ SHUNT VIN-
5 4
AD8211
V+
4 5
CLAMP DIODE INDUCTIVE LOAD BATTERY
5V
OUT
GND
VIN+
INDUCTIVE LOAD CLAMP DIODE SHUNT BATTERY
AD8211
V+
4 5
Figure 26. Battery-Referenced Shunt Resistor
VIN-
5 4
LOW-SIDE CURRENT SENSING
06824-024
SWITCH 5V
Figure 25. Low-Side Switch
HIGH-SIDE CURRENT SENSING
In this configuration, the shunt resistor is referenced to the battery. High voltage is present at the inputs of the current sense amplifier. In this mode, the recirculation current is again measured and shorts to ground can be detected. When the shunt is battery referenced, the AD8211 produces a linear ground-referenced analog output. An AD8214 can also be used to provide an overcurrent detection signal in as little as 100 ns. This feature is useful in high current systems where fast shutdown in overcurrent conditions is essential.
In systems where low-side current sensing is preferred, the AD8211 provides an integrated solution with great accuracy. Ground noise is rejected, CMRR is typically higher than 90 dB, and output linearity is not compromised, regardless of the input differential voltage.
1 3 2 1 3
OUT
GND
VIN+
INDUCTIVE LOAD CLAMP DIODE SWITCH BATTERY
AD8211
V+
4 5
VIN-
5 4
5V
Figure 27. Ground-Referenced Shunt Resistor
Rev. 0 | Page 12 of 16
06824-026
SHUNT
06824-025
SWITCH
AD8211 OUTLINE DIMENSIONS
2.90 BSC
5
4
1.60 BSC
1 2 3
2.80 BSC
PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC
1.45 MAX
0.22 0.08 10 5 0 0.60 0.45 0.30
0.15 MAX
0.50 0.30
SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-178-A A
Figure 28. 5-Lead Small Outline Transistor Package [SOT-23] (RJ-5) Dimensions shown in millimeters
ORDERING GUIDE
Model AD8211YRJZ-R2 1 AD8211YRJZ-RL1 AD8211YRJZ-RL71
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C
Package Description 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23
Package Option RJ-5 RJ-5 RJ-5
Branding Y02 Y02 Y02
Z = RoHS Compliant Part.
Rev. 0 | Page 13 of 16
AD8211 NOTES
Rev. 0 | Page 14 of 16
AD8211 NOTES
Rev. 0 | Page 15 of 16
AD8211 NOTES
(c)2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06824-0-7/07(0)
Rev. 0 | Page 16 of 16

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