AD8213

Dual, High Voltage Current Shunt Monitor AD8213 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 10-lead MSOP: −40°C to +125°C Excellent ac and dc performance 3 μV/°C typical offset drift −10 ppm/°C typical gain drift 120 dB typical CMRR at dc FUNCTIONAL BLOCK DIAGRAM –IN2 +IN2 +IN1 –IN1 A2 PROPRIETARY OFFSET CIRCUITRY OUT2 G = +20 A1 PROPRIETARY OFFSET CIRCUITRY V+ OUT1 G = +20 APPLICATIONS High-side current sensing Motor controls Transmission controls Diesel injection controls Engine management Suspension controls Vehicle dynamic controls DC-to-DC converters CF2 GND CF1 Figure 1. GENERAL DESCRIPTION The AD8213 is a dual-channel, precision current sense amplifier. It features a set gain of 20 V/V, with a maximum ±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 AD8213 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 AD8213 also features additional pins that allow the user to low-pass filter the input signal before amplifying, via an external capacitor to ground. The AD8213 has an operating temperature range of −40ºC to +125ºC and is offered in a small 10-lead MSOP 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 ©2007 Analog Devices, Inc. All rights reserved. 06639-001 AD8213 AD8213 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 Low-Pass Filtering...................................................................... 11 Applications Information .............................................................. 12 High-Side Current Sense with a Low-Side Switch................. 12 High-Side Current Sensing ....................................................... 12 Low-Side Current Sensing ........................................................ 12 Bidirectional Current Sensing .................................................. 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 14 REVISION HISTORY 5/07—Revision 0: Initial Version Rev. 0 | Page 2 of 16 AD8213 SPECIFICATIONS TOPR = operating temperature range, VS = 5 V, RL = 25 kΩ (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 FILTER RESISTOR 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 Min AD8213 Typ Max 20 ±0.25 Unit V/V % % ppm/°C mV mV μV/°C Conditions 0 −10 ±0.5 −25 ±1 ±2.2 ±12 VO ≥ 0.1 V dc TOPR 25°C TOPR TOPR 5 5 3.5 −2 100 80 0.1 250 120 90 0.05 4.95 2 20 500 4.5 2.7 7 70 4.5 2.5 76 −40 +125 5.5 3.75 +65 kΩ MΩ kΩ V mV dB dB V V Ω kΩ kHz V/μs V/μs μV p-p nV/√Hz V mA dB °C V common mode > 5 V V common mode < 5 V Common mode continuous Differential input voltage TOPR, f = DC, VCM > 5 V (see Figure 5) TOPR, f = DC, VCM < 5 V (see Figure 5) 4.9 22 18 CF access to resistor for low-pass filter COUT = 20 pF, no filter capacitor (CF) COUT = 20 pF, CF = 20 pF VCM > 5 V, per amplifier 1 , total supply current for two channels When the input common mode is less than 5 V, the supply current increases. This can be calculated by IS = −0.52(VCM) + 4.9 (see Figure 11). Rev. 0 | Page 3 of 16 AD8213 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 −40°C to +125°C −65°C to +150°C 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 AD8213 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 2 10 9 –IN2 1 +IN2 2 10 –IN1 +IN1 V+ CF1 06639-003 3 8 GND 3 OUT2 4 CF2 5 AD8213 TOP VIEW (Not to Scale) 9 8 7 6 OUT1 4 7 Figure 3. Pin Configuration 06639-002 5 6 Figure 2. Metallization Diagram Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 Mnemonic −IN2 +IN2 GND OUT2 CF2 CF1 OUT1 V+ +IN1 −IN1 X −401 −401 −401 −394 −448 448 394 401 401 401 Y 677 510 −53 −500 −768 −768 −500 −61 510 677 Description Inverting input of the second channel. Noninverting input of the second channel. Ground. Output of the second channel. Low-pass filter pin for the second channel. Low-pass filter pin for the first channel. Output of the first channel. Supply. Noninverting input of the first channel. Inverting input of the first channel. Rev. 0 | Page 5 of 16 AD8213 TYPICAL PERFORMANCE CHARACTERISTICS 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4 –0.5 –0.6 –0.7 06639-104 40 35 30 25 20 15 10 5 0 –5 –10 –15 –20 –25 –30 –35 100k 1M 10M 06639-008 GAIN (dB) VOSI (mV) –0.8 –40 –20 0 20 40 60 80 100 120 –40 10k TEMPERATURE (°C) FREQUENCY (Hz) Figure 4. Typical Offset Drift 130 10 Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p) OUTPUT ERROR (%) (% ERROR OF THE IDEAL OUTPUT VALUE) 120 110 100 COMMON-MODE VOLTAGE > 5V 9 8 7 6 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 250 DIFFERENTIAL INPUT VOLTAGE (mV) 06639-013 06639-010 CMRR (dB) 90 COMMON-MODE VOLTAGE < 5V 80 70 60 50 10 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 5. CMRR vs. Frequency 2500 2000 1500 GAIN ERROR (ppm) 06639-005 –1 Figure 8. Total Output Error vs. Differential Input Voltage –475 –480 –485 1000 500 0 –500 –1000 –1500 –2000 –20 0 20 40 60 80 100 120 06639-102 INPUT BIAS CURRENT (nA) –490 –495 –500 –505 –510 –515 –520 –525 –530 –535 0 25 50 75 –IN +IN –2500 –40 100 125 150 175 200 225 250 TEMPERATURE (°C) DIFFERENTIAL INPUT VOLTAGE (mV) Figure 6. Typical Gain Drift Figure 9. Input Bias Current vs. Differential Input Voltage (VCM = 0 V) (Per Channel) Rev. 0 | Page 6 of 16 AD8213 0.2 0 INPUT 100mV/DIV INPUT BIAS CURRENT (mA) –0.2 OUTPUT –0.4 –0.6 –0.8 –1.0 –1.2 –5 1V/DIV, CF = 20pF OUTPUT 1V/DIV, CF = 100pF 5 15 25 35 45 55 65 06639-011 INPUT COMMON-MODE VOLTAGE (V) TIME (2µs/DIV) Figure 10. Input Bias Current vs. Common-Mode Voltage (Per Input) 7.0 6.5 6.0 Figure 13. Rise Time 200mV/DIV SUPPLY CURRENT (mA) 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 06639-012 INPUT 2V/DIV, CF = 20pF OUTPUT –2 0 2 4 6 8 65 COMMON-MODE VOLTAGE (V) TIME (1µs/DIV) Figure 11. Supply Current vs. Common-Mode Voltage Figure 14. Differential Overload Recovery (Falling) 100mV/DIV INPUT 1V/DIV, CF = 20pF 200mV/DIV INPUT 1V/DIV, CF = 100pF OUTPUT OUTPUT OUTPUT 2V/DIV, CF = 20pF 06639-014 TIME (2µs/DIV) TIME (1µs/DIV) Figure 12. Fall Time Figure 15. Differential Overload Recovery (Rising) Rev. 0 | Page 7 of 16 06639-017 06639-016 1.0 –4 06639-015 AD8213 12 MAXIMUM OUTPUT SOURCE CURRENT (mA) 06639-105 2V/DIV 11 10 9 8 7 6 5 4 3 2 1 –20 0 20 40 60 80 100 120 140 06639-021 06639-024 06639-023 0.01/DIV 0 –40 TIME (5µs/DIV) TEMPERATURE (°C) Figure 16. Settling Time (Falling) 5.0 4.9 4.8 OUTPUT VOLTAGE RANGE (V) Figure 19. Output Source Current vs. Temperature (Per Channel) 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 2V/DIV 0.01/DIV 06639-106 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 OUTPUT SOURCE CURRENT (mA) TIME (5µs/DIV) Figure 17. Settling Time (Rising) 12 OUTPUT VOLTAGE RANGE FROM GND (V) –20 0 20 40 60 80 100 120 140 06639-020 Figure 20. Output Voltage Range vs. Output Source Current (Per Channel) 2.0 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 MAXIMUM OUTPUT SINK CURRENT (mA) 11 10 9 8 7 6 5 4 3 2 1 0 –40 TEMPERATURE (°C) OUTPUT SINK CURRENT (mA) Figure 18. Output Sink Current vs. Temperature (Per Channel) Figure 21. Output Voltage Range from GND vs. Output Sink Current (Per Channel) Rev. 0 | Page 8 of 16 AD8213 2100 1000 1800 TEMP = –40°C TEMP = +25°C TEMP = +125°C 800 1500 1200 900 600 COUNT 400 200 300 06639-006 VOS (µV/°C) –1.5 –1.0 –0.5 0 VOS (mV) 0.5 1.0 1.5 2.0 Figure 22. Offset Drift Distribution (μV/°C) (Temperature Range = −40°C to +125°C) 1400 1200 1000 COUNT Figure 24. Offset Distribution (mV) (VCM = 6 V) 800 600 400 200 0 –24 –21 –18 –15 –12 –9 –6 –3 0 GAIN DRIFT (ppm/°C) Figure 23. Gain Drift Distribution (ppm/°C) (Temperature Range = −40°C to +125°C) 06639-101 Rev. 0 | Page 9 of 16 06639-103 0 –15 COUNT –10 –5 0 5 10 15 600 0 –2.0 AD8213 THEORY OF OPERATION In typical applications, the AD8213 amplifies a small differential input voltage generated by the load current flowing through a shunt resistor. The AD8213 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 25 shows a simplified schematic of the AD8213. The following explanation refers exclusively to Channel 1 of the AD8213, however, the same explanation applies to Channel 2. A load current flowing through the external shunt resistor produces a voltage at the input terminals of the AD8213. The input terminals are connected to Amplifier A1 by Resistor R1(1) and Resistor R1(2). The inverting terminal, which has very high input impedance is held to (VCM) – (ISHUNT × RSHUNT), since negligible current flows through Resistor R1(2). Amplifier A1 forces the noninverting input to the same potential. Therefore, the current that flows through Resistor R1(1), is equal to IIN1 = (ISHUNT1 × RSHUNT1)/R1(1) ISHUNT2 RSHUNT2 IIN2 R2 (1) R2 (2) IIN1 R1 (1) R1 (2) ISHUNT1 RSHUNT1 This current (IIN1) is converted back to a voltage via ROUT1. 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 VOUT1 = (ISHUNT1 × RSHUNT1) × 20 Prior to the buffer amplifier, a precision-trimmed 20 kΩ resistor is available to perform low-pass filtering of the input signal prior to the amplification stage. This means that the noise of the input signal is not amplified, but rejected, resulting in a more precise output signal that will directly interface with a converter. A capacitor from the CF1 pin to GND, will result in a low-pass filter with a corner frequency of f −3dB = 1 2 π(20000 )C FILTER A2 PROPRIETARY OFFSET CIRCUITRY OUT2 = (ISHUNT2 × RSHUNT2 ) × 20 G = +20 20kΩ ROUT2 A1 PROPRIETARY OFFSET CIRCUITRY 20kΩ ROUT1 G = +20 V+ Q2 Q1 OUT1 = (ISHUNT1 × RSHUNT1 ) × 20 CF2 GND CF1 Figure 25. Simplified Schematic Rev. 0 | Page 10 of 16 06639-028 AD8213 AD8213 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 AD8213 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 26 displays the input differential voltage versus the corresponding output voltage at different common modes. 220 200 180 160 140 LOW-PASS FILTERING In typical applications, such as motor and solenoid current sensing, filtering the differential input signal of the AD8213 could be beneficial in reducing differential common-mode noise as well as transients and current ripples flowing through the input shunt resistor. Typically, such a filter can be implemented by adding a resistor in series with each input and a capacitor directly between the input pins. However, the AD8213 features a filter pin available after the input stage, but before the final amplification stage. The user can connect a capacitor to ground, making a low-pass filter with the internal precisiontrimmed 20 kΩ resistor. This means the no gain or CMRR errors are introduced by adding resistors at the input of the AD8213. Figure 27 shows the typical connection. ISHUNT2 RSHUNT2 R2 (1) VOUT @ VCM = 65V ISHUNT1 RSHUNT1 R1 (1) R1 (2) VOUT (mV) 120 100 80 60 40 20 0 1 2 3 4 5 6 7 8 9 10 06639-029 R2 (2) VOUT @ VCM = 0V A2 PROPRIETARY OFFSET CIRCUITRY 20kΩ A1 PROPRIETARY OFFSET CIRCUITRY 20kΩ G = +20 V+ 0 IDEAL VOUT G = +20 VIN DIFFERENTIAL (mV) AD8213 CF2 CAP2 GND CF1 06639-030 Figure 26. Gain Linearity Due to Differential and Common-Mode Voltage The AD8213 provides a correct output voltage, regardless of the common mode, when the input differential is at least 2 mV. This 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 in order to provide sufficient guardbands. The ability of the AD8213 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. CAP1 Figure 27. Filter Capacitor Connections The 3 dB frequency of this low-pass filter is calculated using the following formula: f −3dB = 1 2 π(20000 )C FILTER It is recommended that in order to prevent output chatter due to noise potentially entering through the filter pin and coupling to the output, a capacitor is always placed from the filter pin to GND. This can be a ≈20 pF capacitor in cases when all of the bandwidth of the AD8213 is needed in the application. Rev. 0 | Page 11 of 16 AD8213 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 28). 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. INDUCTIVE LOAD CLAMP DIODE BATTERY SHUNT 1 2 3 4 5 OVERCURRENT DETECTION (