ANALOG DEVICES AD8207

Zero-Drift, High Voltage, Bidirectional Difference Amplifier AD8207 FEATURES FUNCTIONAL BLOCK DIAGRAM V+ Ideal for current shunt applications EMI filters included +IN ZERO 1 μV/°C maximum input offset drift OUT DRIFT –IN High common-mode voltage range AD8207 −4 V to +65 V operating (5 V supply) −4 V to +35 V operating (3.3 V supply) −25 V to +75 V survival V 1 REF Gain = 20 V/V RANGE REF 3.3 V to 5.5 V supply range V 2 REF Wide operating temperature range: −40°C to +125°C Bidirectional current monitoring <500 nV/°C typical offset drift GND <10 ppm/°C typical gain drift Figure 1. >90 dB CMRR dc to 10 kHz Qualified for automotive applications APPLICATIONS High-side current sensing in Motor control Solenoid control Engine management Electric power steering Suspension control Vehicle dynamic control DC-to-DC converters GENERAL DESCRIPTION The AD8207 is a single-supply difference amplifier ideal for The AD8207 is ideal for bidirectional current sensing amplifying small differential voltages in the presence of large applications. It features two reference pins,VREF1 and VREF2, common-mode voltage. The operating input common-mode that allow the user to easily offset the output of the device to voltage range extends from −4 V to +65 V with a 5 V supply. any voltage within the supply range. With V 1 attached to the REF The AD8207 works with a single-supply voltage of 3.3 V to 5 V, V+ pin and V 2 attached to the GND pin, the output is set at REF and is ideally suited to withstand large input PWM common- half scale. Attaching both pins to GND causes the output to mode voltages, typical in solenoid and motor control applications. be unipolar, starting near ground. Attaching both pins to V+ causes the output to be unipolar starting near V+. Other output The AD8207 is available in an 8-lead SOIC package. Excellent offsets are achieved by applying an external low impedance dc performance over temperature keeps errors in the mea- voltage to the VREF1 and VREF2 pins. surement loop to a minimum. Offset drift is typically less than 500 nV/°C, and gain drift is typically below 10 ppm/°C. 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 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 © 2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 09160-001 AD8207 TABLE OF CONTENTS Features .............................................................................................. 1 Output Offset Adjustment ............................................................ 12 Applications ....................................................................................... 1 Unidirectional Operation .......................................................... 12 Functional Block Diagram .............................................................. 1 Bidirectional Operation ............................................................. 12 General Description ......................................................................... 1 External Referenced Output ..................................................... 13 Revision History ............................................................................... 2 Splitting the Supply .................................................................... 13 Specif ica t ions ..................................................................................... 3 Splitting an External Reference ................................................ 13 Absolute Maximum Ratings ............................................................ 4 Applications Information .............................................................. 14 ESD Caution .................................................................................. 4 Motor Control ............................................................................. 14 Pin Configuration and Function Descriptions ............................. 5 Solenoid Control ........................................................................ 15 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 16 Theory of Operation ...................................................................... 10 Ordering Guide .......................................................................... 16 Power Supply Adjustment ............................................................. 11 Automotive Products ................................................................. 16 3.3 V to 4.5 V Supply Operation .............................................. 11 4.5 V to 5.5 V Supply Operation .............................................. 11 REVISION HISTORY 7/10—Revision 0: Initial Version Rev. 0 | Page 2 of 16 AD8207 SPECIFICATIONS TOPR = −40°C to +125°C, V+ = 5 V or 3.3 V, unless otherwise noted. Table 1. Parameter Min Typ Max Unit Test Conditions/Comments GAIN Initial 20 V/V Accuracy over Temperature −0.3 +0.3 % TOPR Gain vs. Temperature −15 0 ppm/°C TOPR VOLTAGE OFFSET 1 Offset Voltage (RTI) ±100 μV 25°C 1 Over Temperature (RTI) ±400 μV TOPR Offset Drift −1 +1 μV/°C TOPR INPUT Input Impedance Differential 240 kΩ Common Mode 126 kΩ Input Voltage Range −4 +65 V Common mode, continuous, V+ = 5 V, T OPR −4 +35 V Common mode continuous, V+ = 3.3 V, TOPR 2 250 mV Differential , V+ = 5 V Common-Mode Rejection (CMRR) 80 90 dB TOPR, f = dc to 20 kHz OUTPUT Output Voltage Range 0.02 V+ − 0.05 V RL = 25 kΩ, TOPR Output Resistance 2 Ω DYNAMIC RESPONSE Small-Signal −3 dB Bandwidth 150 kHz TOPR Slew Rate 1 V/μs NOISE 1 0.1 Hz to 10 Hz, (RTI) 20 μV p-p 1 Spectral Density, 1 kHz, (RTI) 0.6 μV/√Hz OFFSET ADJUSTMENT 3 Ratiometric Accuracy 0.497 0.503 V/V Divider to supplies, TOPR 4 Accuracy (RTO) ±3 mV/V Voltage applied to V 1 and V 2 in parallel, REF REF T OPR Output Offset Adjustment Range 0.02 V+ − 0.05 V T OPR 5 VREF Input Voltage Range 0.0 V+ V VREF Divider Resistor Values 100 kΩ POWER SUPPLY 6 Operating Range 4.5 5.5 V RANGE (Pin 4) connected to GND 7 3.3 4.5 V RANGE (Pin 4) connected to V+ Quiescent Current over Temperature 2.5 mA V = 0.1 V dc O Power Supply Rejection Ratio (PSRR) 80 dB TEMPERATURE RANGE For Specified Performance −40 +125 °C 1 RTI = referred to input. 2 Input voltage range = ±125 mV with half-scale offset. The input differential range also depends on the supply voltage. The maximum input differential range can be calculated by V+/20. 3 The offset adjustment is ratiometric to the power supply when V 1 and V 2 are used as a divider between the supplies. REF REF 4 RTO = referred to output. 5 The reference pins should be driven with a low impedance voltage source to maintain the specified accuracy of the AD8207. 6 With a 4.5 V to 5.5 V supply, the RANGE pin should be tied low. In this mode, the common-mode range of the AD8207 is −4 V to +65 V. 7 With a 3.3 V to 4.5 V supply, the RANGE pin should be tied to V+. In this mode, the common-mode range of the AD8207 is −4 V to +35 V. If a 4.5 V supply is used, the user can tie RANGE high or low depending on the common-mode range needed in the application. Rev. 0 | Page 3 of 16 AD8207 ABSOLUTE MAXIMUM RATINGS Stresses above those listed under Absolute Maximum Ratings Table 2. may cause permanent damage to the device. This is a stress Parameter Rating rating only and functional operation of the device at these or Supply Voltage 12.5 V any other conditions above those indicated in the operational Continuous Input Voltage −25 V to +75 V section of this specification is not implied. Exposure to absolute Input Transient Survival −30 V to +80 V maximum rating conditions for extended periods may affect Differential Input Voltage −25 V to +75 V device reliability. Reverse Supply Voltage 0.3 V Operating Temperature Range −40°C to +125°C Storage Temperature Range −65°C to +150°C ESD CAUTION Output Short-Circuit Duration Indefinite Rev. 0 | Page 4 of 16 AD8207 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS –IN 1 8 +IN AD8207 GND 2 7 V 1 REF V 2 3 6 V+ TOP VIEW REF (Not to Scale) RANGE 4 5 OUT Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. Mnemonic Description 1 −IN Negative Input. 2 GND Ground Pin. 3 V2 Reference Input. REF 4 RANGE Range Pin. This pin switches between 4.5 V to 5.5 V and 3.3 V to 4.5 V supply operation. 5 OUT Output. 6 V+ Supply Pin. 7 V1 Reference Input. REF 8 +IN Positive Input. Rev. 0 | Page 5 of 16 09160-002 AD8207 TYPICAL PERFORMANCE CHARACTERISTICS –10 40 –12 30 –14 20 –16 10 –18 0 –20 –10 –22 –20 –24 –30 –26 –40 –28 –50 –30 –60 –40 –20 0 20 40 60 80 100 120 140 1k 10k 100k 1M 10M TEMPERATURE (°C) FREQUENCY (Hz) Figure 3. Typical Offset Drift vs. Temperature Figure 6. Typical Small-Signal Bandwidth (V = 200 mV p-p) OUT 140 19 130 16 120 13 110 10 100 7 90 4 80 1 70 60 –2 100 1k 10k 100k 1M 0 5 10 15 20 25 30 35 40 45 50 FREQUENCY (Hz) DIFFERENTIAL INPUT VOLTAGE (mV) Figure 4. Typical CMRR vs. Frequency Figure 7. Total Output Error vs. Differential Input Voltage 500 600 400 500 300 400 200 300 100 0 200 3.3V –100 100 –200 5V 0 –300 –100 –400 –500 –200 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 –40 –20 0 20 40 60 80 100 120 140 V (V) TEMPERATURE (°C) CM Figure 5. Typical Gain Error vs. Temperature Figure 8. Input Bias Current vs. Common-Mode Voltage Rev. 0 | Page 6 of 16 GAIN ERROR (ppm) CMRR (dB) V (µV) OSI 09160-004 09160-003 09160-005 GAIN (dB) BIAS CURRENT PER INPUT PIN (µA) TOTAL OUTPUT ERROR (%) 09160-121 09160-116 09160-006 AD8207 2.0 100mV/DIV 1.8 INPUT 1.6 5V 1 1.0V/DIV 1.4 3.3V OUTPUT 1.2 V+ = 3.3V 2 1.0 –5 5 152535 455565 TIME (1µs/DIV) INPUT COMMON-MODE VOLTAGE (V) Figure 9. Supply Current vs. Input Common-Mode Voltage Figure 12. Fall Time (V+ = 3.3 V) 100mV/DIV INPUT INPUT 100mV/DIV 1 1 OUTPUT 2.0V/DIV OUTPUT V+ = 5V 1.0V/DIV V+ = 3.3V 2 2 TIME (1µs/DIV) TIME (1µs/DIV) Figure 10. Rise Time (V+ = 3.3 V) Figure 13. Fall Time (V+ = 5 V) INPUT INPUT 200mV/DIV 100mV/DIV 1 1 OUTPUT OUTPUT V+ = 5V V+ = 3.3V 2.0V/DIV 2.0V/DIV 2 2 TIME (1µs/DIV) TIME (10µs/DIV) Figure 11. Rise Time (V+ = 5 V) Figure 14. Differential Overload Recovery, Rising (V+ = 3.3 V) Rev. 0 | Page 7 of 16 SUPPLY CURRENT (mA) 09160-008 09160-007 09160-115 09160-111 09160-110 09160-009 AD8207 INPUT 200mV/DIV INPUT COMMON MODE 1 50V/DIV OUTPUT OUTPUT 50mV/DIV 2.0V/DIV V+ = 5V 2 TIME (10µs/DIV) TIME (2µs/DIV) Figure 15. Differential Overload Recovery, Rising (V+ = 5 V) Figure 18. Input Common-Mode Step Response (V+ = 5 V, Inputs Shorted) 7.0 6.5 6.0 200mV/DIV 5.5 INPUT 5.0 1 5V 4.5 3.3V 4.0 3.5 OUTPUT 2.0V/DIV 3.0 V+ = 3.3V 2.5 2 2.0 –40 –20 0 20 40 60 80 100 120 140 TIME (10µs/DIV) TEMPERATURE (°C) Figure 16. Differential Overload Recovery, Falling (V+ = 3.3 V) Figure 19. Maximum Output Sink Current vs. Temperature 10 9 8 200mV/DIV INPUT 5V 7 1 6 3.3V 5 4 OUTPUT 2.0V/DIV 3 V+ = 5V 2 2 1 –40 –20 0 20 40 60 80 100 120 140 TIME (10µs/DIV) TEMPERATURE (°C) Figure 20. Maximum Output Source Current vs. Temperature Figure 17. Differential Overload Recovery, Falling (V+ = 5 V) Rev. 0 | Page 8 of 16 09160-114 09160-113 09160-112 MAXIMUM OUTPUT SINK CURRENT (mA) MAXIMUM OUTPUT SOURCE CURRENT (mA) 09160-122 09160-118 09160-117 AD8207 0 600 –40°C –100 500 +25°C +125°C –200 400 –300 300 –400 200 –500 100 –600 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 –400 –300 –200 –100 0 100 200 300 400 OUTPUT SOURCE CURRENT (mA) OFFSET (µV) Figure 21. Output Voltage Range vs. Output Source Current Figure 23. Input Offset Distribution 1000 1000 800 800 600 600 400 400 200 200 0 0 –14 –12 –10 –8 –6 –4 –2 0 012345678 OUTPUT SINK CURRENT (mA) GAIN DRIFT (ppm/°C) Figure 22. Output Voltage Range from GND vs. Output Sink Current Figure 24. Gain Drift Distribution Rev. 0 | Page 9 of 16 OUTPUT VOLTAGE FROM GROUND (mV) VOLTAGE FROM POSITIVE RAIL (mV) 09160-119 09160-120 COUNT COUNT 09160-023 09160-024 AD8207 THEORY OF OPERATION The AD8207 is a single-supply, zero drift, difference amplifier The reference inputs, VREF1 and VREF2, are tied through 100 kΩ that uses a unique architecture to accurately amplify small resistors to the positive input of the main amplifier, which differential current shunt voltages in the presence of rapidly allows the output offset to be adjusted anywhere in the output changing common-mode voltage. operating range. The gain is 1 V/V from the reference pins to the output when the reference pins are used in parallel. When In typical applications, the AD8207 is used to measure current the pins are used to divide the supply, the gain is 0.5 V/V. by amplifying the voltage across a shunt resistor connected to its inputs. The AD8207 offers breakthrough performance without compromising any of the robust application needs typical The AD8207 includes a zero-drift amplifier, a precision resistor of solenoid or motor control. The part rejects PWM input network, a common-mode control amplifier, and a precision common-mode voltages, while the zero-drift architecture yields reference (see Figure 25). the lowest offset and offset drift performance on the market. A set of precision-trimmed resistors make up the network SHUNT that attenuates the input common-mode voltage to within the +IN –IN supply range of the amplifier, in this case with a ratio of 20/1. This attenuation ensures that when the input pins are externally 120kΩ 120kΩ ZERO-DRIFT AMPLIFIER at the common-mode extremes of −4 V and +65 V, the actual 100kΩ voltage at the inputs of the main amplifier is still within the OUT 9kΩ 60kΩ 60kΩ supply range. 100kΩ The input resistor network also attenuates normal (differential) 6kΩ 6kΩ 100kΩ 50kΩ mode voltages. Therefore, the total internal gain of the AD8207 is set to 400 V/V to provide a total system gain of 20 V/V. V 1 REF 100kΩ COMMON-MODE V 2 Total Gain (V/V) = 1/20 (V/V) × 400 (V/V) = 20 V/V REF CONTROL AMPLIFIER 100kΩ The AD8207 is designed to provide excellent common-mode 3.5V/2.2V AD8207 rejection, even with PWM common-mode inputs that can REF change at very fast rates, for example, 1 V/ns. An internal GND common-mode control amplifier is used to maintain the input common mode of the main amplifier at 3.5 V (with 5 V supply), Figure 25. Simplified Schematic and therefore eliminates the negative effects of such fast- changing external common-mode variations. The AD8207 features an input offset drift of less than 500 nV/°C. This performance is achieved through a novel zero-drift architecture that does not compromise band- width, which is typically rated at 150 kHz. Rev. 0 | Page 10 of 16 09160-025 AD8207 POWER SUPPLY ADJUSTMENT 3.3 V TO 4.5 V SUPPLY OPERATION 4.5 V TO 5.5 V SUPPLY OPERATION The AD8207 can operate with a single-supply voltage as low In most applications, the AD8207 operates with a single 5 V as 3.3 V to 4.5 V. This mode of operation is achieved by con- supply. In this mode, the operating input common-mode necting the RANGE pin (Pin 4) to the supply (see Figure 26). range of the AD8207 is rated from −4 V to +65 V. To operate It is recommended that an external resistor be placed in series the device with a 5 V supply (includes 4.5 V to 5.5 V), connect from the RANGE pin to the supply. This resistor can be a the RANGE pin (Pin 4) to logic low, or GND, as shown in typical 5 kΩ 1% resistor. Figure 27. SHUNT SHUNT 1 8 1 8 AD8207 AD8207 3.3V 5V 2 7 2 7 3 6 3 6 TOP VIEW TOP VIEW 3.3V (Not to Scale) (Not to Scale) 4 5 OUT 4 5 OUT Figure 26. 3.3 V Supply Operation Figure 27. 5 V Supply Bidirectional Operation Note that in this mode of operation, the common-mode range The output and reference input ranges are limited to the of the AD8207 is limited to −4 V to +35 V. The output and supply voltage used. With a supply voltage from 4.5 V to 5.5 V, reference input ranges are limited to the supply of the part. The the RANGE pin (Pin 4) should be connected to GND to achieve user can have a 4.5 V supply and connect the RANGE pin from the maximum input common-mode range specification of −4 V 3.3 V to 4.5 V. Alternatively, the user can connect the RANGE to +65 V. pin as high as 4.5 V, with the supply from 3.3 V to 4.5 V. Rev. 0 | Page 11 of 16 09160-010 09160-011 AD8207 OUTPUT OFFSET ADJUSTMENT The output of the AD8207 can be adjusted for unidirectional or V+ Referenced Output Mode bidirectional operation. The V+ referenced output mode is set when both reference pins are tied to the positive supply. This mode is typically used when UNIDIRECTIONAL OPERATION the diagnostic scheme requires detection of the amplifier and Unidirectional operation allows the AD8207 to measure the wiring before power is applied to the load (see Figure 29). currents through a resistive shunt in one direction. The basic 5V modes for unidirectional operation are ground referenced output mode and V+ referenced output mode. V+ For unidirectional operation, the output can be set at the +IN negative rail (near ground) or at the positive rail (near V+) OUT ZERO when the differential input is 0 V. The output moves to the –IN DRIFT opposite rail when a correct polarity differential input voltage AD8207 is applied. In this case, full scale is approximately 250 mV for a 5 V supply or 165 mV for a 3.3 V supply. The required polarity V 1 REF of the differential input depends on the output voltage setting. RANGE If the output is set at the positive rail, the input polarity must REF V 2 be negative to move the output down. If the output is set at REF ground, the polarity must be positive to move the output up. Ground Referenced Output Mode GND When using the AD8207 in the ground referenced output mode, Figure 29. V+ Referenced Output Mode, V+ = 5 V both reference inputs are tied to ground, which causes the output to sit at the negative rail when there are 0 differential volts at the input Table 5. V+ Referenced Output (see Figure 28). VIN (Referred to −IN) VO 5V V+ = 5 V 0 V 4.95 V V+ −250 mV 0.02 V +IN V+ = 3.3 V OUT ZERO –IN DRIFT 0 V 3.25 V −165 mV 0.02 V AD8207 BIDIRECTIONAL OPERATION V 1 REF Bidirectional operation allows the AD8207 to measure currents RANGE REF through a resistive shunt in two directions. In this case, the V 2 REF 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 GND the bidirectional current is asymmetrical. Figure 28. Ground Referenced Output Mode, V+ = 5 V Table 6. V = (V+/2) with V = 0 V O IN Table 4. Ground Referenced Output V (Referred to −IN) V IN O VIN (Referred to −IN) VO V+ = 5 V V+ = 5 V +100 mV 4.5 V −100 mV 0.5 V 0 V 0.02 V V+ = 3.3 V 250 mV 4.95 V +67.5 mV 3 V V+ = 3.3 V 0 V 0.02 V −67.5 mV 0.3 V 165 mV 3.25 V Adjusting the output is accomplished by applying voltages to the reference inputs. V 1 and V 2 are tied to internal REF REF resistors that connect to an internal offset node. There is no operational difference between the pins. Rev. 0 | Page 12 of 16 09160-012 09160-013 AD8207 5V EXTERNAL REFERENCED OUTPUT Tying both reference pins together and to an external reference V+ produces an output equal to the reference voltage when there is +IN no differential input (see Figure 30). The output moves down ZERO OUT –IN DRIFT from the reference voltage when the input is negative, relative to the −IN pin, and up when the input is positive, relative to the AD8207 −IN pin. The reference pins are connected to the positive input V 1 of the main amplifier via precision-trimmed 100 kΩ resistors. REF Therefore, it is recommended that a low impedance voltage is RANGE REF always be used to set the reference voltage. If external resistors are connected directly to the VREF1 and VREF2 pins, there will V 2 REF be a mismatch with the internal trimmed resistors, leading to offset gain accuracy reduction. GND 5V Figure 31. Splitting the Supply, V+ = 5 V V+ SPLITTING AN EXTERNAL REFERENCE +IN ZERO OUT –IN DRIFT In Figure 32, an external reference is divided by 2 with an accuracy of approximately 0.5% by connecting one V pin to REF AD8207 ground and the other V pin to the reference (see Figure 32). REF 5V V 1 REF RANGE VOLTAGE V+ 2.5V REF REFERENCE +IN V 2 ZERO REF OUT DRIFT –IN GND AD8207 Figure 30. External Referenced Output, V+ = 5 V V 1 REF VOLTAGE 5V REFERENCE SPLITTING THE SUPPLY RANGE REF 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 dif- V 2 REF ferential input (see Figure 31). The benefit is that no external GND reference is required to offset the output for bidirectional current measurement. This creates a midscale offset that is ratiometric to the supply, which means that if the supply increases or decreases, Figure 32. Splitting an External Reference, V+ = 5 V 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. Rev. 0 | Page 13 of 16 09160-014 09160-015 09160-016 AD8207 APPLICATIONS INFORMATION directions by using the shunt available at the motor. This is MOTOR CONTROL a better solution than a ground referenced op amp because 3-Phase Motor Control ground is not typically a stable reference voltage in this type The AD8207 is ideally suited for monitoring current in 3-phase of application. The instability of the ground reference causes motor applications. inaccuracies in the measurements that could be made with a The 150 kHz typical bandwidth of the AD8207 allows for simple ground referenced op amp. The AD8207 measures instantaneous current monitoring. Additionally, the typical current in both directions as the H-bridge switches and the low offset drift of 500 nV/°C means that the measurement motor changes direction. The output of the AD8207 is config- error between the two motor phases will be at a minimum ured in an external referenced bidirectional mode (see the over temperature. The AD8207 rejects PWM input common- Bidirectional Operation section). mode voltages in the range of −4 V to +65 V (with a 5 V supply). Monitoring the current on the motor phase allows CONTROLLER 5V for sampling of the current at any point and allows for diagnostic information such as a short to GND and battery. +IN 1 +V OUT V REF S MOTOR Refer to Figure 34 for a typical phase current measurement AD8207 5V setup with the AD8207. SHUNT –IN GND V 2RANGE REF H-Bridge Motor Control 2.5V Another typical application for the AD8207 is as part of the control loop in H-bridge motor control. In this case, the shunt resistor is placed in the middle of the H-bridge (see Figure 33. H-Bridge Motor Control Application Figure 33) so that it can accurately measure current in both V+ M I U I V I W V– 5V 5V INTERFACE AD8214 CIRCUIT AD8207 AD8207 OPTIONAL PART FOR OVERCURRENT CONTROLLER PROTECTION AND FAST (DIRECT) BIDIRECTIONAL CURRENT MEASUREMENT SHUTDOWN OF REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–4V TO +65V) POWER STAGE AMPLIFICATION HIGH OUTPUT DRIVE Figure 34. 3-Phase Motor Control Rev. 0 | Page 14 of 16 09160-017 09160-020 AD8207 High-Side Current Sense with a High-Side Switch SOLENOID CONTROL This configuration minimizes the possibility of unexpected High-Side Current Sense with a Low-Side Switch solenoid activation and excessive corrosion (see Figure 36). In Other typical applications for the AD8207 include current Figure 36, both the switch and the shunt are on the high side. monitoring for PWM control of solenoid openings. Typical When the switch is off, the battery is removed from the load, applications include hydraulic valve control, diesel injection which prevents damage from potential shorts to ground, while control, and actuator control. still allowing the recirculation current to be measured and In Figure 35, the PWM control switch is ground referenced. An providing for diagnostics. Removing the power supply from the inductive load (solenoid) is tied to a power supply. A resistive load for the majority of the time minimizes the corrosive effects shunt is placed between the switch and the load (see Figure 35). that can be caused by the differential voltage between the load An advantage of placing the shunt on the high side is that the and ground. When using a high-side switch, the battery voltage entire current, including the recirculation current, can be is connected to the load when the switch is closed, causing the measured because the shunt remains in the loop when the common-mode voltage to increase to the battery voltage. When switch is off. In addition, diagnostics capabilities are enhanced the switch is opened, the voltage reversal across the inductive because shorts to ground can be detected with the shunt on load causes the common-mode voltage to be held one diode the high side. In this circuit configuration, when the switch drop below ground by the clamp diode. is closed, the common-mode voltage moves down to near the 5V negative rail. When the switch is opened, the voltage reversal SWITCH across the inductive load causes the common-mode voltage to be held one diode drop above the battery by the clamp diode. +IN V 1 +V OUT REF S 5V SHUNT INDUCTIVE 42V AD8207 LOAD BATTERY –IN GND V 2 RANGE REF CLAMP DIODE INDUCTIVE CLAMP +IN V 1 +V OUT REF S LOAD DIODE SHUNT 42V AD8207 BATTERY –IN GND V 2 RANGE REF Figure 36. High-Side Switch SWITCH Figure 35. Low-Side Switch Rev. 0 | Page 15 of 16 09160-018 09160-019 AD8207 OUTLINE DIMENSIONS 5.00(0.1968) 4.80(0.1890) 85 6.20(0.2441) 4.00(0.1574) 1 5.80(0.2284) 3.80(0.1497) 4 0.50(0.0196) 1.27(0.0500) 45° BSC 1.75(0.0688) 0.25(0.0099) 1.35(0.0532) 0.25(0.0098) 8° 0.10(0.0040) 0° 0.51(0.0201) COPLANARITY 1.27(0.0500) 0.10 0.31(0.0122) 0.25(0.0098) SEATING 0.40(0.0157) PLANE 0.17(0.0067) COMPLIANTTOJEDECSTANDARDSMS-012-AA CONTROLLINGDIMENSIONSAREINMILLIMETERS;INCHDIMENSIONS (INPARENTHESES)AREROUNDED-OFFMILLIMETEREQUIVALENTSFOR REFERENCEONLYANDARENOTAPPROPRIATEFORUSEINDESIGN. Figure 37. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) ORDERING GUIDE 1, 2 Model Temperature Range Package Description Package Option AD8207WBRZ −40°C to +125°C 8-Lead SOIC_N R-8 AD8207WBRZ-R7 −40°C to +125°C 8-Lead SOIC_N, 7” Tape and Reel R-8 AD8207WBRZ-RL −40°C to +125°C 8-Lead SOIC_N, 13” Tape and Reel R-8 1 Z = RoHS Compliant Part. 2 W = Qualified for Automotive Applications. AUTOMOTIVE PRODUCTS The AD8207 models are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these models. ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09160-0-7/10(0) Rev. 0 | Page 16 of 16 012407-A