AD8210

High Voltage, Bidirectional Current Shunt Monitor AD8210 FEATURES ±4000 V HBM ESD High common-mode voltage range −2 V to +65 V operating −5 V to +68 V survival Buffered output voltage 5 mA output drive capability Wide operating temperature range: −40°C to +125°C Ratiometric half-scale output offset Excellent ac and dc performance 3 μV/°C typical offset drift 10 ppm/°C typical gain drift 120 db typical CMRR at dc 80 db typical CMRR at 100 kHz Available in 8-lead SOIC VSUPPLY FUNCTIONAL BLOCK DIAGRAM IS RS +IN –IN V+ VS AD8210 LOAD VREF 1 G = +20 VOUT APPLICATIONS Current sensing Motor controls Transmission controls Diesel injection controls Engine management Suspension controls Vehicle dynamic controls DC-to-DC converters GND VREF 2 Figure 1. GENERAL DESCRIPTION The AD8210 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 −2 V to +65 V. The typical supply voltage is 5 V. The AD8210 is offered in a SOIC package. The operating temperature range is −40°C to +125°C. Excellent ac and dc performance over temperature keep errors in the measurement loop to a minimum. Offset drift and gain drift are guaranteed to a maximum of 8 μV/°C and 20 ppm/°C, respectively. The output offset can be adjusted from 0.05 V to 4.9 V with a 5 V supply by using VREF1 pin and 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 ©2006 Analog Devices, Inc. All rights reserved. 05147-001 AD8210 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 Modes of Operation ....................................................................... 11 Unidirectional Operation.......................................................... 11 Bidirectional Operation............................................................. 11 Input Filtering ................................................................................. 13 Applications..................................................................................... 14 High-Side Current Sense with a Low-Side Switch................. 14 High-Side Current Sense with a High-Side Switch ............... 14 H-Bridge Motor Control ........................................................... 14 Outline Dimensions ....................................................................... 15 Ordering Guide .......................................................................... 15 REVISION HISTORY 4/06—Revision 0: Initial Version Rev. 0 | Page 2 of 16 AD8210 SPECIFICATIONS TA = operating temperature range, VS = 5 V, unless otherwise noted. Table 1. Parameter GAIN Initial Accuracy Accuracy Over Temperature Gain Drift VOLTAGE OFFSET Offset Voltage (RTI) Over Temperature (RTI) Offset Drift INPUT Input Impedance Differential Common Mode Common Mode Common-Mode Input Voltage Range Differential Input Voltage Range Common-Mode Rejection AD8210 SOIC 1 Min Typ Max 20 ±0.5 ±0.7 20 ±1.0 ±1.8 ±8.0 Unit V/V % % ppm/°C mV mV μV/°C Conditions 25°C, VO ≥ 0.1 V dc TA 25°C TA 2 5 3.5 −2 100 80 80 250 120 95 80 +65 kΩ MΩ kΩ V mV dB dB dB dB V Ω kHz V/μs μV p-p nV/√Hz V common mode > 5 V V common mode < 5 V Common mode, continuous Differential 2 TA, f = dc, VCM > 5 V TA, f = dc to 100 kHz 3 , VCM < 5 V TA, f = 100 kHz3, VCM > 5 V TA, f = 40 kHz3, VCM > 5 V RL = 25 kΩ OUTPUT Output Voltage Range Output Impedance 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 4 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 0.05 2 450 3 7 70 0.499 0.05 0.0 24 4.5 80 −40 4.9 32 5.0 0.501 ±0.6 4.9 VS 40 5.5 2 V/V mV/V V V kΩ V mA dB °C Divider to supplies Voltage applied to VREF1 and VREF2 in parallel VS = 5 V VCM > 5 V 5 +125 TMIN to TMAX = −40°C to +125°C. Differential input voltage range = ±125 mV with half-scale output offset. Source imbalance 5 V) Figure 9. Fall Time Rev. 0 | Page 6 of 16 05147-017 05147-014 05147-033 –2000 –40 AD8210 4V/DIV 100mV/DIV 0.02%/DIV 500mV/DIV 05147-018 05147-024 05147-019 05147-025 400ns/DIV 4µs/DIV Figure 10. Rise Time Figure 13. Settling Time (Falling) 200mV/DIV 4V/DIV 0.02%/DIV 2V/DIV 1µs/DIV 05147-016 4µs/DIV Figure 11. Differential Overload Recovery (Falling) Figure 14. Settling Time (Rising) 50V/DIV 200mV/DIV 2V/DIV 05147-015 100mV/DIV 1µs/DIV 1µs/DIV Figure 12. Differential Overload Recovery (Rising) Figure 15. Common-Mode Response (Falling) Rev. 0 | Page 7 of 16 AD8210 5.0 4.9 4.8 OUTPUT VOLTAGE RANGE (V) 05147-020 50V/DIV 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 100mV/DIV 1µs/DIV 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 OUTPUT SOURCE CURRENT (mA) Figure 16. Common-Mode Response (Rising) 8 7 6 5 4 3 2 1 0 –40 Figure 19. Output Voltage Range vs. Output Source Current 1.4 OUTPUT VOLTAGE RANGE FROM GND (V) MAXIMUM OUTPUT SINK CURRENT (mA) 1.2 1.0 0.8 0.6 0.4 0.2 0 TEMPERATURE (°C) OUTPUT SINK CURRENT (mA) Figure 17. Output Sink Current vs. Temperature 11 Figure 20.Output Voltage Range from GND vs. Output Sink Current 6.0 5.5 5.0 SUPPLY CURRENT (mA) MAXIMUM OUTPUT SOURCE CURRENT (mA) 10 9 8 7 6 5 4 3 2 1 –20 0 20 40 60 80 100 120 140 05147-026 4.5 4.0 3.5 3.0 2.5 2.0 1.5 0 2 4 6 8 65 05147-027 0 –40 1.0 –2 TEMPERATURE (°C) COMMON-MODE VOLTAGE (V) Figure 18. Output Source Current vs. Temperature Figure 21. Supply Current vs. Common-Mode Voltage Rev. 0 | Page 8 of 16 05147-038 –20 0 20 40 60 80 100 120 140 05147-022 0 1 2 3 4 5 6 7 8 9 05147-023 AD8210 2100 1800 1500 3000 COUNT 4000 +125°C +25°C –40°C COUNT 1200 900 600 2000 1000 300 0 –10 –9 0 –2.0 05147-034 –6 –3 0 3 6 9 10 VOS DRIFT (µV/°C) VOS (mV) Figure 22. Offset Drift Distribution (μV/°C), SOIC, Temperature Range = −40°C to +125°C Figure 24. Offset Distribution (μV), SOIC, VCM = 5 V 3500 3000 2500 COUNT 4000 3500 3000 2500 2000 1500 +125°C +25°C –40°C 2000 1500 1000 500 0 COUNT 1000 500 0 –2.0 GAIN DRIFT (PPM/°C) VOS (mV) Figure 23. Gain Drift Distribution (PPM/°C), SOIC, Temperature = −40°C to +125°C Figure 25. Offset Distribution (μV), SOIC, VCM = 0 V Rev. 0 | Page 9 of 16 05147-037 0 3 6 9 12 15 18 20 05147-035 –1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 05147-036 –1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 AD8210 THEORY OF OPERATION In typical applications, the AD8210 amplifies a small differential input voltage generated by the load current flowing through a shunt resistor. The AD8210 rejects high common-mode voltages (up to 65 V) and provides a ground referenced buffered output that interfaces with an analog-to-digital converter. Figure 26 shows a simplified schematic of the AD8210. The AD8210 is comprised of two main blocks, a differential amplifier and an instrumentation amplifier. A load current flowing through the external shunt resistor produces a voltage at the input terminals of the AD8210. The input terminals are connected to the differential amplifier (A1) by Resistor R1 and Resistor R2. A1 nulls the voltage appearing across its own input terminals by adjusting the current through R1 and R2 with Transistor Q1 and Transistor Q2. When the input signal to the AD8210 is 0 V, the currents in R1 and R2 are equal. When the differential signal is nonzero, the current increases through one of the resistors and decreases in the other. The current difference is proportional to the size and polarity of the input signal. The differential currents through Q1 and Q2 are converted into a differential voltage by R3 and R4. A2 is configured as an instrumentation amplifier. The differential voltage is converted into a single-ended output voltage by A2. The gain is internally set with precision trimmed, thin film resistors to 20 V/V. The output reference voltage is easily adjusted by the VREF1 pin and VREF2 pin. In a typical configuration, VREF1 is connected to VCC while VREF2 is connected to GND. In this case, the output is centered at VCC/2 when the input signal is 0 V. ISHUNT RSHUNT R1 R2 VS A1 AD8210 Q1 Q2 VREF 1 VOUT = (ISHUNT × RSHUNT ) × 20 A2 R3 R4 VREF 2 Figure 26. Simplified Schematic Rev. 0 | Page 10 of 16 05147-004 GND AD8210 MODES OF OPERATION The AD8210 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 wiring before power is applied to the load (see Figure 28 and Table 5). RS +IN –IN UNIDIRECTIONAL OPERATION Unidirectional operation allows the AD8210 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. In 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 ground, then the polarity needs to be positive to move the output up (see Table 5). If the output is set at the positive rail, then the input polarity needs to be negative to move the output down (see Table 6). VS AD8210 0.1µF VREF 1 OUTPUT G = +20 Ground Referenced Output When using the AD8210 in this mode, both reference inputs are tied to ground, which causes the output to sit at the negative rail when the differential input voltage is zero (see Figure 27 and Table 4). RS +IN –IN GND VREF 2 Figure 28. V+ Referenced Output Table 5. V+ = 5 V VS 0.1µF VIN (Referred to −IN) 0V −250 mV VO 4.9 V 0.05 V AD8210 BIDIRECTIONAL OPERATION Bidirectional operation allows the AD8210 to measure currents through a resistive shunt in two directions. The output offset can be set anywhere within the output range. Typically, it is set at half scale for equal measurement 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 05147-005 VREF 1 OUTPUT G = +20 VREF 2 GND VIN (Referred to –IN) +125 mV −125 mV VO 4.9 V 0.05 V Figure 27. Ground Referenced Output Table 4. V+ = 5 V VIN (Referred to −IN) 0V 250 mV VO 0.05 V 4.9 V Adjusting the output can also be accomplished by applying voltage(s) to the reference inputs. Rev. 0 | Page 11 of 16 05147-006 AD8210 External Referenced Output Tying both VREF pins together to an external reference produces an output offset at the reference voltage when there is no differential input (see Figure 29). When the input is negative relative to the −IN pin, the output moves down from the reference voltage. When the input is positive relative to the −IN pin, the output increases. RS +IN –IN RS +IN –IN VS 0.1µF AD8210 VREF 1 VREF 0V ≤ VREF ≤ VS VS G = +20 0.1µF OUTPUT AD8210 VREF VREF 2 OUTPUT G = +20 Figure 30. Split External Reference Splitting the Supply VREF 2 Figure 29. External Reference Output Splitting an External Reference In this case, an external reference is divided by two with an accuracy of approximately 0.2% by connecting one VREF pin to ground and the other VREF pin to the reference voltage (see Figure 30). Note that Pin VREF1 and Pin VREF2 are tied to internal precision resistors that connect to an internal offset node. There is no operational difference between the pins. For proper operation, the AD8210 output offset should not be set with a resistor voltage divider. Any additional external resistance could create a gain error. A low impedance voltage source should be used to set the output offset of the AD8210. 05147-007 GND By tying one reference pin to V+ and the other to the GND pin, the output is set at mid supply when there is no differential input (see Figure 31). This mode is beneficial because no external reference is required to offset the output for bidirectional current measurement. This creates a midscale offset that is ratiometric to the supply, meaning that if the supply increases or decreases, the output still remains at half scale. 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 also increases by 10% (2.75 V). RS +IN –IN VS AD8210 0.1µF VREF 1 G = +20 OUTPUT VREF 2 GND 05147-009 Figure 31. Split Supply Rev. 0 | Page 12 of 16 05147-008 VREF 1 0V ≤ VREF ≤ VS GND AD8210 INPUT FILTERING In typical applications such as motor and solenoid current sensing, filtering at the input of the AD8210 can be beneficial in reducing differential noise, as well as transients and current ripples flowing through the input shunt resistor. An input lowpass filter can be implemented as shown in Figure 32. The 3 dB frequency for this filter can be calculated using the following formula: f _ 3 dB = 1 2 π × R FILTER × C FILTER Adding outside components such as RFILTER and CFILTER introduces additional errors to the system. To minimize these errors as much as possible, it is recommended that RFILTER be 10 Ω or lower. By adding the RFILTER in series with the 2 kΩ internal input resistors of the AD8210, a gain error is introduced. This can be calculated using the following formula: (1) ⎛ ⎞ 2 kΩ ⎟ Gain Error (%) = 100 − ⎜100 × ⎜ 2 kΩ − RFILTER ⎟ ⎝ ⎠ (2) RSHUNT < RFILTER RFILTER ≤ 10Ω CFILTER RFILTER ≤ 10Ω +IN –IN VS 0.1µF AD8210 VREF VREF 1 0V ≤ VREF ≤ VS G = +20 OUTPUT VREF 2 GND 05147-013 Figure 32. Input Low-Pass Filtering Rev. 0 | Page 13 of 16 AD8210 APPLICATIONS The AD8210 is ideal for high-side or low-side current sensing. Its accuracy and performance benefits applications such as 3-phase and H-bridge motor control, solenoid control, as well as power supply current monitoring. BATTERY 5V 0.1µF SWITCH +IN SHUNT CLAMP DIODE –IN VREF 1 +VS OUT For solenoid control, two typical circuit configurations are used: high-side current sense with a low-side switch, and high-side current sense with a high-side switch. AD8210 GND VREF 2 NC 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 33). 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 short circuits to ground can be detected with the shunt on the high side. 5V INDUCTIVE LOAD 0.1µF NC = NO CONNECT Figure 34. High-Side Switch Using a high-side switch connects the battery voltage to the load when the switch is closed. This causes the common-mode 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. H-BRIDGE MOTOR CONTROL Another typical application for the AD8210 is as part of the control loop in H-bridge motor control. In this case, the AD8210 is placed in the middle of the H-bridge (see Figure 35) so that it can accurately measure current in both directions by using the shunt available at the motor. This configuration is beneficial for measuring the recirculation current to further enhance the control loop diagnostics. 05147-010 CLAMP DIODE BATTERY SHUNT +IN VREF 1 +VS OUT AD8210 –IN GND VREF 2 NC SWITCH 5V 0.1µF CONTROLLER NC = NO CONNECT Figure 33. Low-Side Switch In this circuit configuration, when the switch is closed, the common-mode voltage moves down to 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. MOTOR +IN SHUNT –IN VREF 1 +VS OUT AD8210 GND VREF 2 NC 5V HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH This configuration minimizes the possibility of unexpected solenoid activation and excessive corrosion (see Figure 34). In this case, both the switch and the shunt are on the high side. When the switch is off, the battery is removed from the load, which prevents damage from potential short circuits to ground, while still allowing the recirculation current to be measured and diagnostics to be preformed. 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. NC = NO CONNECT Figure 35. Motor Control Application The AD8210 measures current in both directions as the H-bridge switches and the motor changes direction. The output of the AD8210 is configured in an external reference bidirectional mode; see the Modes of Operation section. Rev. 0 | Page 14 of 16 05147-012 2.5V 05147-011 HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH INDUCTIVE LOAD AD8210 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) × 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-012-AA 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 36. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) ORDERING GUIDE Model AD8210YRZ 1 AD8210YRZ-REEL1 AD8210YRZ-REEL71 1 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C Package Description 8-Lead SOIC_N 8-Lead SOIC_N, 13” Tape and Reel 8-Lead SOIC_N, 7” Tape and Reel Package Option R-8 R-8 R-8 Z = Pb-free part. Rev. 0 | Page 15 of 16 AD8210 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05147-0-4/06(0) Rev. 0 | Page 16 of 16