ANALOG DEVICES AD8212

High Voltage Current Shunt Monitor AD8212 FEATURES FUNCTIONAL BLOCK DIAGRAM V V+ SENSE Adjustable gain 1 8 High common-mode voltage range AD8212 7 V to 65 V typical 7 V to >500 V with external pass transistor Current output Integrated 5 V series regulator 8-lead MSOP package Operating temperature range of −40°C to +125°C APPLICATIONS Current shunt measurement OUTPUT Motor controls CURRENT COMPENSATION DC-to-DC converters BIAS CIRCUIT Power supplies 5 2 3 6 Battery monitoring I COM BIAS ALPHA OUT Remote sensing Figure 1. GENERAL DESCRIPTION The AD8212 is a high common-mode voltage, current shunt Another feature of the AD8212 is high voltage operation, monitor. It accurately amplifies a small differential input voltage which is achieved by using an external high voltage breakdown in the presence of large common-mode voltages up to 65 V PNP transistor. In this configuration, the common-mode range (>500 V with an external PNP transistor). of the AD8212 is equal to the breakdown of the external PNP transistor. Therefore, operation at several hundred volts is easily The AD8212 is ideal for current monitoring across a shunt achieved (see Figure 23). resistor in applications controlling loads, such as motors and solenoids. The current output of the device is proportional to The AD8212 features a patented output base current compensa- the input differential voltage. The user can select an external tion circuit for high voltage operation mode. This ensures that resistor to set the desired gain. The typical common-mode no base current is lost through the external transistor and voltage range of the AD8212 is 7 V to 65 V. excellent output accuracy is maintained regardless of common- mode voltage or temperature. Rev. B 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 ©2007–2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 05942-001 AD8212 TABLE OF CONTENTS Features .............................................................................................. 1 Normal Operation (7 V to 65 V Supply (V+) Range) ..............9 Applications ....................................................................................... 1 High Voltage Operation Using an External PNP Transistor 10 Functional Block Diagram .............................................................. 1 Output Current Compensation Circuit ................................... 10 General Description ......................................................................... 1 Applications Information .............................................................. 11 Revision History ............................................................................... 2 General High-Side Current Sensing ........................................ 11 Specif ica t ions ..................................................................................... 3 Motor Control ............................................................................. 11 Absolute Maximum Ratings ............................................................ 4 500 V Current Monitor ............................................................. 11 ESD Caution .................................................................................. 4 Bidirectional Current Sensing .................................................. 12 Pin Configuration and Function Descriptions ............................. 5 Outline Dimensions ....................................................................... 13 Typical Performance Characteristics ............................................. 6 Ordering Guide .......................................................................... 13 Theory of Operation ........................................................................ 9 REVISION HISTORY 5/09—Rev. A to Rev. B Changes to Ordering Guide .......................................................... 13 11/07—Rev. 0 to Rev. A Increased Operating Temperature Range ........................ Universal 5/07—Revision 0: Initial Version Rev. B | Page 2 of 16 AD8212 SPECIFICATIONS VS = 15 V, TOPR = −40°C to +125°C, TA = 25°C, unless otherwise noted. Table 1. Parameter Conditions/Comments Min Typ Max Unit SUPPLY VOLTAGE (V+) No external pass transistor 7 65 V 1 With external PNP transistor 7 >500 V 2 SUPPLY CURRENT (I = I + I) SUPPLY OUT BIAS V+ = 7 V to 65 V 220 720 μA High voltage operation, using external PNP 200 1500 μA VOLTAGE OFFSET Offset Voltage (RTI) T ±2 mV A Over Temperature (RTI) T ±3 mV OPR Offset Drift TOPR ±10 μV/°C INPUT Input Impedance Differential 2 kΩ Common Mode (VCM) V+ = 7 V to 65 V 5 MΩ Voltage Range Differential Maximum voltage between V+ and V 500 mV SENSE 3 V (Pin 8) Current V+ = 7 V to 65 V, T 100 200 nA SENSE OPR OUTPUT Transconductance 1000 μA/V Current Range (I ) 7 V ≤ V+ ≤ 65 V, 0 mV to 500 mV differential input 500 μA OUT Gain Error for TOPR 7 V ≤ V+ ≤ 65 V, with respect to 500 μA full scale ±1 % Impedance 20 MΩ Voltage Range 0 V+ − 5 V REGULATOR Nominal Value 7 V ≤ V+ ≤ 65 V 4.80 5 5.20 V PSRR 7 V ≤ V+ ≤ 65 V 80 dB Bias Current (I) T , 7 V ≤ V+ ≤ 65 V 185 200 μA BIAS OPR TOPR, high voltage operation 200 1000 μA DYNAMIC RESPONSE Small Signal −3 dB Bandwidth Gain = 10 1000 kHz Gain = 20 500 kHz Gain = 50 100 kHz Settling Time Within 0.1% of the true output, gain = 20 2 μs ALPHA PIN INPUT CURRENT 25 μA NOISE 0.1 Hz to 10 Hz, RTI 1.1 μV p-p Spectral Density, 1 kHz, RTI 40 nV/√Hz TEMPERATURE RANGE For Specified Performance (TOPR) −40 +125 °C 1 Range dependent on the VCE breakdown of the transistor. 2 The AD8212 supply current in normal voltage operation (V+ = 7 V to 65 V) is the bias current (I ) added to output current (I ). Output current varies upon input BIAS OUT differential voltage and can range from 0 μA to 500 μA. IBIAS in this mode of operation is typically 185 μA and 200 μA maximum. For high voltage operation mode, refer to the High Voltage Operation Using an External PNP Transistor section. 3 The current of the amplifier into VSENSE (Pin 8) increases when operating in high voltage mode. See the High Voltage Operation Using an External PNP Transistor section for more information. Rev. B | Page 3 of 16 AD8212 ABSOLUTE MAXIMUM RATINGS ESD CAUTION TOPR = −40°C to +125°C, unless otherwise noted. Table 2. Parameter Rating Supply Voltage 65 V Continuous Input Voltage 68 V Reverse Supply Voltage 0.3 V Operating Temperature Range −40°C to +125°C Storage Temperature Range −40°C to +150°C Output Short-Circuit Duration 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. Rev. B | Page 4 of 16 AD8212 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS V+ 1 8 V SENSE 1 8 COM 2 AD8212 7 NC 2 BIAS 3 6 ALPHA TOP VIEW 6 (Not to Scale) NC 4 5 I OUT 3 5 NC = NO CONNECT Figure 2. Pin Configuration Figure 3. Metallization Diagram Table 3. Pin Function Descriptions Pin No. Mnemonic X Coordinate Y Coordinate Description 1 V+ −393 +219 Supply Voltage (Inverting Amplifier Input). 2 COM −392 +67 Regulator Low Side. 3 BIAS −392 −145 Bias Circuit Low Side. 4 NC – – No Connect. 5 I +386 −82 Output Current. OUT 6 ALPHA +386 +23 Current Compensation Circuit Input. 7 NC +386 +118 No Connect. 8 VSENSE +386 +210 Noninverting Amplifier Input. Rev. B | Page 5 of 16 05942-002 05942-025 AD8212 TYPICAL PERFORMANCE CHARACTERISTICS 195 1200 190 T = +125°C 1000 185 800 180 T = +25°C T = –40°C 600 175 400 170 200 165 160 0 5 10 15 20 2530 3540 45 5055 60 65 –40 –20 0 20 40 60 80 100 120 SUPPLY VOLTAGE (V) TEMPERATURE (°C) Figure 4. Supply Current vs. Supply (Pin V+) (IOUT = 0 mA) Figure 7. Input Offset Voltage vs. Temperature 5.2 1.0 0.9 +125°C 0.8 5.1 0.7 T = –40°C T = +25°C 0.6 5.0 +25°C 0.5 0.4 –40°C 0.3 4.9 0.2 T = +125°C 0.1 4.8 0 5 10 15 20 2530 3540 45 5055 60 65 7 1217 22 27 3237 42 47 52 57 62 SUPPLY VOLTAGE (V) VOLTAGE SUPPLY (V) Figure 5. Regulator Voltage vs. Supply (Pin V+) Figure 8 .Input Offset Voltage vs. Supply (Pin V+) 50 10 45 9 40 8 G = +50 35 7 30 6 G = +20 25 5 20 4 G = +10 15 3 10 2 5 1 0 0 1k 10k 100k 1M 10M 0 50 100 150 200 250 300 350 400 450 500 DIFFERENTIAL INPUT VOLTAGE (mV) FREQUENCY (Hz) Figure 6. Gain vs. Frequency Figure 9. Output Current Drift vs. Differential Input Voltage Rev. B | Page 6 of 16 REGULATOR VOLTAGE (V) QUIESCENT CURRENT (µA) GAIN (dB) 05942-021 05942-006 05942-005 OUTPUT CURRENT DRIFT (nA/°C) INPUT V (µV) OFFSET VOLTAGE RTI (mV) OS 05942-009 05942-010 05942-008 AD8212 100 V IN 20mV/DIV 10 V+ = 15V R = 50kΩ OUT 1 G = +10 V OUT 500mV/DIV G = +20 0V 0.1 G = +50 0.01 5µs/DIV 0 10 203040 50 60 70 80 90 100 500 DIFFERENTIAL INPUT VOLTAGE (mV) Figure 10. Total Output Error Due to Input Offset vs. Differential Figure 13. Step Response (Gain = 50) Input Voltage V IN V IN 20mV/DIV 100mV/DIV V+ = 15V V+ = 15V R = 5kΩ OUT R = 5kΩ OUT V OUT V OUT 50mV/DIV 200mV/DIV 0V 5µs/DIV 5µs/DIV Figure 11. Step Response (Gain = 5) Figure 14. Step Response (Gain = 5) V IN V IN 20mV/DIV 100mV/DIV V+ = 15V V+ = 15V R = 20kΩ OUT R = 20kΩ OUT V OUT V OUT 1V/DIV 200mV/DIV 0V 0V 5µs/DIV 5µs/DIV Figure 15. Step Response (Gain = 20) Figure 12. Step Response (Gain = 20) Rev. B | Page 7 of 16 OUTPUT ERROR (%) 05942-013 05942-012 05942-023 05942-015 05942-014 05942-016 AD8212 5.2 V IN 100mV/DIV 5.1 T = –40°C V+ = 15V R = 50kΩ OUT T = +25°C 5.0 V OUT 2V/DIV T = +125°C 0V 4.9 4.8 5µs/DIV 100 200 300 400 500 600 700 800 900 1000 1100 1200 BIAS CURRENT (µA) Figure 16. Step Response (Gain = 50) Figure 19. Regulator Voltage High Voltage Mode (IOUT = 0 mA) vs. Bias Current 5.2 V IN 100mV/DIV 5.1 V+ = 300V V+ = 15V V+ = 100V 5.0 R = 20kΩ OUT V+ = 200V V OUT 2V/DIV 4.9 0V 4.8 2µs/DIV –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Figure 17. Step Response Falling Figure 20. Regulator Voltage vs. Temperature (High Voltage Operation) 550 V 500 IN 100mV/DIV 450 400 350 V+ = 15V R = 20kΩ OUT 300 250 200 V+ MAXIMUM RANGE V 150 OUT V+ MINIMUM RANGE 2V/DIV 0V 100 50 0 2µs/DIV 10 20 30 50 70 100 150 200 250 300 350 400 450 500 R (kΩ) BIAS Figure 18. Step Response Rising Figure 21. Supply Range (V+) vs. Bias Resistor Value (High Voltage Operation) Rev. B | Page 8 of 16 05942-019 05942-018 05942-017 REGULATOR VOLTAGE (V) V+ OPERATING RANGE (V) REGULATOR VOLTAGE (V) 05942-020 05942-007 05942-024 AD8212 I LOAD BATTERY R SHUNT THEORY OF OPERATION 1 8 NORMAL OPERATION AD8212 (7 V TO 65 V SUPPLY (V+) RANGE) R1 R2 In typical applications, the AD8212 measures a small differential input voltage generated by a load current flowing through a shunt resistor. A1 The operational amplifier (A1) is connected across the shunt resistor (R ) with its inverting input connected to the SHUNT Q1 battery/supply side, and the noninverting input connected to the load side of the system. Amplifier A1 is powered via an internal series regulator (depicted as a Zener diode in Figure 22). This regulator maintains a constant 5 V between OUTPUT CURRENT the battery/supply terminal of the AD8212 and COM (Pin 2), COMPENSATION BIAS which represents the lowest common point of the internal CIRCUIT circuitry. 5 2 3 6 A load current flowing through the external shunt resistor VOUT I OUT produces a voltage at the input terminals of the AD8212. R OUT Amplifier A1 responds by causing Transistor Q1 to conduct the necessary current through Resistor R1 to equalize the potential at both the inverting and noninverting inputs of Amplifier A1. Figure 22. Typical Connection (7 V to 65 V Supply (Pin V+) Range) The current through the emitter of Transistor Q1 (IOUT) is When using the AD8212 as described, the battery/supply proportional to the input voltage (V ), and, therefore, the SENSE voltage in the system must be between 7 V to 65 V. The 7 V load current (I ) through the shunt resistor (R ). The LOAD SHUNT minimum supply range is necessary to turn on the internal output current (I ) is converted to a voltage by using an OUT regulator (shown as a Zener diode in Figure 22). This regulated external resistor, the value of which is dependent on the input voltage then remains a constant 5 V, regardless of the supply to output gain equation desired in the application. (V+) voltage. The 65 V maximum limit in this mode of operation is due to the breakdown voltage limitation of the The transfer function for the AD8212 is AD8212 process. IOUT = (gm × VSENSE) Typically, a 1% resistor can be used to convert the output V = I × R SENSE LOAD SHUNT current to a voltage. Table 4 provides suggested R values. OUT V = I × R OUT OUT OUT Table 4. Suggested ROUT Values V = (V × R )/1000 OUT SENSE OUT Gain (V/V) ROUT (kΩ) where: 1 1 gm = 1000 µA/V. 10 10 20 20 In normal voltage operation mode, the bias circuit is connected 50 49.9 to GND, as shown in Figure 22. In this mode, I is typically BIAS 100 100 185 μA throughout the 7 V to 65 V (V+) range. Rev. B | Page 9 of 16 LOAD 05942-003 AD8212 In this mode of operation, the supply current (I ) of the HIGH VOLTAGE OPERATION USING AN EXTERNAL BIAS AD8212 circuit increases based on the supply range and the PNP TRANSISTOR R resistor chosen. For example BIAS The AD8212 offers features that simplify measuring current in if the presence of common-mode voltages greater than 65 V. This is achieved by connecting an external PNP transistor at the V+ = 500 V and RBIAS = 500 kΩ output of the AD8212, as shown in Figure 23. The VCE break- IBIAS = (V+ − 5 V)/RBIAS down voltage of this PNP becomes the operating common-mode then, range of the AD8212. PNP transistors with breakdown voltages exceeding 300 V are inexpensive and readily available in small I = (500 – 5)/500 kΩ = 990 μA BIAS packages. In high voltage operation, it is recommended that I remain BIAS BATTERY R SHUNT within 200 μA to 1 mA. This ensures that the bias circuit is 1 8 turned on, allowing the device to function as expected. At the AD8212 same time, the current through the bias circuit/regulator is R1 R2 limited to 1 mA. Refer to Figure 19 and Figure 21 for IBIAS and V+ information when using the AD8212 in a high voltage configuration. A1 When operating the AD8212, as depicted in Figure 23, Transistor Q2 can be a FET or a bipolar PNP transistor. The latter is much less expensive, however the magnitude of I OUT Q1 conducted to the output resistor (ROUT) is reduced by the amount of current lost through the base of the PNP. This leads to an error in the output voltage reading. OUTPUT CURRENT The AD8212 includes an integrated patented circuit, which COMPENSATION BIAS compensates for the output current that is lost through the base CIRCUIT of the external PNP transistor. This ensures that the correct 5 2 3 6 transconductance of the amplifier is maintained. The user can opt for an inexpensive bipolar PNP, instead of a FET, while Q2 maintaining a comparable level of accuracy. VOUT R R OUT BIAS OUTPUT CURRENT COMPENSATION CIRCUIT The base of the external PNP, Q2, is connected to ALPHA (Pin 6) of the AD8212. The current flowing in this path is Figure 23. High Voltage Operation Using External PNP mirrored inside the current compensation circuit. This The AD8212 features an integrated 5 V series regulator. This current then flows in Resistor R2, which is the same value regulator ensures that at all times COM (Pin 2), which is the as Resistor R1. The voltage created by this current across most negative of all the terminals, is always 5 V less than the Resistor R2, displaces the noninverting input of Amplifier A1 supply voltage (V+). Assuming a battery voltage (V+) of 100 V, by the corresponding voltage. Amplifier A1 responds by driving it follows that the voltage at COM (Pin 2) is the base of Transistor Q1 so as to force a similar voltage (V+) – 5 V = 95 V displacement across Resistor R1, thereby increasing I . OUT The base emitter junction of Transistor Q2, in addition to the Because the current generated by the output compensation Vbe of one internal transistor, makes the collector of Transistor Q1 circuit is equal to the base current of Transistor Q2, and the approximately equal to resulting displacements across Resistor R1 and Resistor R2 result in equal currents, the increment of current added to the output 95 V + 2(Vbe(Q2)) = 95 V + 1.2 V = 96.2 V current is equivalent to the base current of Transistor Q2. This voltage appears across external Transistor Q2. The voltage Therefore, the integrated output current compensation circuit across Transistor Q1 is has corrected I such that no error results from the base OUT 100 V – 96.2 V = 3.8 V current lost at Transistor Q2. In this manner, Transistor Q2 withstands 95.6 V and the This feature of the AD8212 greatly improves IOUT accuracy and internal Transistor Q1 is only subjected to voltages well below allows the user to choose an inexpensive bipolar PNP (with low its breakdown capability. beta) with which to monitor current in the presence of high voltages (typically several hundred volts). Rev. B | Page 10 of 16 LOAD 05942-004 AD8212 APPLICATIONS INFORMATION 500 V CURRENT MONITOR GENERAL HIGH-SIDE CURRENT SENSING As noted in the High Voltage Operation Using an External PNP The AD8212 output is intended to drive high impedance nodes. Transistor section, the AD8212 common-mode voltage range is Therefore, if interfacing with a converter, it is recommended extended by using an external PNP transistor. This mode of that the output voltage across R be buffered, so that the gain OUT operation is achievable with many amplifiers featuring a current of the AD8212 is not affected. output. However, typically an external Zener regulator must be I LOAD added, along with a FET device, to withstand the common-mode BATTERY R SHUNT voltage and maintain output current accuracy. The AD8212 features an integrated regulator (which acts as a AD8212 Zener regulator). It offers output current compensation that 1 V+ V 8 SENSE allows the user to maintain excellent output current accuracy 2 COM 7 NC by using any PNP transistor. Reliability is increased due to 3 BIAS 6 ALPHA ADC lower component count. Most importantly, the output current 4 NC I 5 OUT AD8661 accuracy is high, allowing the user to choose an inexpensive I PNP transistor to withstand the increased common-mode R OUT OUT voltage. I LOAD NOTES 1. NC = NO CONNECT. 500V R SHUNT Figure 24. Normal Voltage Range Operation Careful calculations must be made when choosing a gain AD8212 resistor so as not to exceed the input voltage range of the 1 V+ V 8 SENSE converter. The output of the AD8212 can be as high as 2 COM NC 7 VOUT 3 BIAS 6 (V+) − 5 V. However, the true output maximum voltage is ALPHA 4 NC I 5 OUT dependent upon the differential input voltage, and the resulting R OUT output current across ROUT, which can be as high as 500 μA 500kΩ (based on a 500 mV maximum input differential limit). MOTOR CONTROL NOTES 1. TRANSISTOR V BREAKDOWN CE The AD8212 is a practical solution for high-side current sensing VOLTAGE MUST BE 500V. 2. NC = NO CONNECT. in motor control applications. In cases where the shunt resistor Figure 26. High Voltage Operation Using External PNP is referenced to battery and the current flowing is unidirectional, as shown in Figure 25, the AD8212 monitors the current with no additional supply pin necessary. BATTERY I AD8212 MOTOR 1 V+ V 8 SENSE 2 COM 7 NC 3 BIAS 6 ALPHA MOTOR 4 NC I 5 V OUT OUT R OUT NOTES 1. NC = NO CONNECT. Figure 25. High-Side Current Sensing for Motor Control Rev. B | Page 11 of 16 LOAD 05942-026 05942-028 LOAD 05942-027 AD8212 BIDIRECTIONAL CURRENT SENSING The AD8212 is a unidirectional current sensing device. VOUT1 increases as ILOAD flows through the shunt resistor. VOUT2 Therefore, in power management applications where both the increases when ICHARGE flows through the input shunt resistor. charge and load currents must be monitored, two devices can be used and connected as shown in Figure 27. In this case, I LOAD I CHARGE R SHUNT V+ V V V+ SENSE SENSE 1 8 8 1 AD8212 AD8212 OUTPUT OUTPUT CURRENT CURRENT COMPENSATION COMPENSATION BIAS BIAS CIRCUIT CIRCUIT I COM BIAS ALPHA ALPHA BIAS COM I OUT OUT 5 2 3 6 6 3 2 5 V 1 V 2 OUT OUT R 1 R 2 OUT OUT Figure 27. Bidirectional Current Sensing Rev. B | Page 12 of 16 BATTERY CHARGE LOAD 05942-011 AD8212 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 5 5.15 3.20 4.90 3.00 4.65 2.80 1 4 PIN 1 0.65 BSC 0.95 0.85 1.10 MAX 0.75 0.80 8° 0.15 0.38 0.60 0.23 0° 0.00 0.22 0.40 0.08 SEATING COPLANARITY PLANE 0.10 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 28. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model Temperature Range Package Description Package Option Branding 1 AD8212YRMZ −40°C to +125°C 8-Lead MSOP RM-8 Y04 1 AD8212YRMZ-RL −40°C to +125°C 8-Lead MSOP, 13” Tape and Reel RM-8 Y04 1 AD8212YRMZ-R7 −40°C to +125°C 8-Lead MSOP, 7” Tape and Reel RM-8 Y04 1 AD8212WYRMZ −40°C to +125°C 8-Lead MSOP RM-8 Y25 1 AD8212WYRMZ-RL −40°C to +125°C 8-Lead MSOP, 13” Tape and Reel RM-8 Y25 1 AD8212WYRMZ-R7 −40°C to +125°C 8-Lead MSOP, 7” Tape and Reel RM-8 Y25 1 Z = RoHS Compliant Part. Rev. B | Page 13 of 16 AD8212 NOTES Rev. B | Page 14 of 16 AD8212 NOTES Rev. B | Page 15 of 16 AD8212 NOTES ©2007–2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05942-0-5/09(B) Rev. B | Page 16 of 16