AD8418AWBRMZ-10

Bidirectional, Zero Drift, Current Sense Amplifier AD8418A Data Sheet FEATURES GENERAL DESCRIPTION Typical 0.1 μV/°C offset drift Maximum ±200 μV voltage offset over full temperature range 2.7 V to 5.5 V power supply operating range Electromagnetic interference (EMI) filters included High common-mode input voltage range −2 V to +70 V, continuous operation −3 V to +80 V, continuous survival Minimum DC common-mode rejection ratio (CMRR): 90 dB Initial gain = 20 V/V Wide operating temperature range AD8418AWB and AD8418AB: −40°C to +125°C AD8418AWH: −40°C to +150°C Bidirectional operation Available in 8-lead SOIC_N, 8-lead MSOP, and FMEA tolerant 10-lead MSOP pinout AEC-Q100 qualified for automotive applications The AD8418A is a high voltage, high resolution current shunt amplifier. It features an initial gain of 20 V/V, with a maximum ±0.15% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8418A offers excellent input common-mode rejection from −2 V to +70 V. The AD8418A performs bidirectional current measurements across a shunt resistor in a variety of automotive and industrial applications, including motor control, power management, and solenoid control. The AD8418A offers breakthrough performance throughout the −40°C to +150°C temperature range. It features a zero drift core, which leads to a typical offset drift of 0.1 μV/°C throughout the operating temperature range and the common-mode voltage range. The AD8418A is qualified for automotive applications. The device includes EMI filters and patented circuitry to enable output accuracy with pulse-width modulation (PWM) type input common-mode voltages. The typical input offset voltage is ±100 μV. The AD8418A is offered in an 8-lead MSOP and an 8-lead SOIC_N package with a 10-lead MSOP pinout option engineered for failure mode and effects analysis (FMEA). APPLICATIONS High-side current sensing in Motor controls Solenoid controls Power management Low-side current sensing Diagnostic protection Table 1. Related Devices Part No. AD8205 AD8206 AD8207 AD8210 AD8417 Description Current sense amplifier, gain = 50 Current sense amplifier, gain = 20 High accuracy current sense amplifier, gain = 20 High speed current sense amplifier, gain = 20 High accuracy current sense amplifier, gain = 60 FUNCTIONAL BLOCK DIAGRAM VCM = –2V TO +70V VS = 2.7V TO 5.5V 70V VS AD8418A VCM +IN 0V ISHUNT EMI FILTER VOUT OUT G = 20 –IN VS + RSHUNT 50A VREF 1 VS/2 EMI FILTER – ISHUNT VREF 2 11883-001 0V GND –50A Figure 1. Rev. E Document Feedback 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 ©2013–2020 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD8418A Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1  Bidirectional Operation ............................................................ 12  Applications ...................................................................................... 1  External Referenced Output ..................................................... 13  General Description ......................................................................... 1  Splitting the Supply .................................................................... 13  Functional Block Diagram .............................................................. 1  Splitting an External Reference ................................................ 13  Revision History ............................................................................... 2  Applications Information ............................................................. 14  Specifications .................................................................................... 3  Motor Control ............................................................................ 14  Absolute Maximum Ratings ........................................................... 4  Solenoid Control ........................................................................ 15  ESD Caution.................................................................................. 4  Pinout Option Engineered for FMEA ..................................... 16  Pin Configuration and Function Descriptions ............................ 5  Outline Dimensions ....................................................................... 17  Typical Performance Characteristics ............................................. 6  Ordering Guide .......................................................................... 18  Theory of Operation ...................................................................... 11  Automotive Products ................................................................ 18  Output Offset Adjustment ............................................................ 12  Unidirectional Operation.......................................................... 12  REVISION HISTORY 6/2020—Rev. D to Rev. E Changes to Features Section and General Description Section ........................................................... 1 Changes to Figure 2 Caption and Table 4 Title ........................... 6 Added Figure 3 and Table 5; Renumbered Sequentially ............ 6 Added Pinout Option Engineered for FMEA Section, Table 6, and Table 7 ...................................................................................... 17 Updated Outline Dimensions ....................................................... 19 Changes to Ordering Guide .......................................................... 19 12/2018—Rev. C to Rev. D Changes to Features Section ........................................................... 1 Changes to Table 3 ........................................................................... 4 5/2018—Rev. B to Rev. C Changes to Input Bias Current Parameter, Table 2..................... 3 Changes to Figure 20 ....................................................................... 8 4/2017—Rev. A to Rev. B Changes to Features Section and General Description Section .......1 Changes to Table 2 ............................................................................3 Changes to Table 3 ............................................................................4 Change to Figure 18 ..........................................................................8 Added Figure 19 and Figure 20; Renumbered Sequentially........8 12/2014—Rev. 0 to Rev. A Added AD8418AWH ........................................................ Universal Changes to Features Section and General Description Section ....... 1 Changes to Specifications Section and Table 2 .............................3 Changes to Table 3 ............................................................................4 Changes to Ordering Guide .......................................................... 16 11/2013—Revision 0: Initial Version Rev. E | Page 2 of 18 Data Sheet AD8418A SPECIFICATIONS TA = −40°C to +125°C (operating temperature range) for the AD8418AWB, TA = −40°C to +150°C for the AD8418AWH, VS = 5 V, unless otherwise noted. Table 2. Parameter GAIN Initial Error Over Temperature Gain vs. Temperature VOLTAGE OFFSET Offset Voltage, Referred to the Input, RTI Over Temperature, RTI Offset Drift INPUT Input Bias Current Input Voltage Range Common-Mode Rejection Ratio (CMRR) OUTPUT Output Voltage Range Output Resistance Maximum Capacitive Load 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 Accuracy1 Accuracy, Referred to the Output (RTO) Output Offset Adjustment Range POWER SUPPLY Operating Range Quiescent Current Over Temperature Power Supply Rejection Ratio TEMPERATURE RANGE For Specified Performance 1 Test Conditions/Comments Min Typ Max Unit ±0.15 +5 V/V % ppm/°C ±200 +0.4 μV μV μV/°C 260 μA μA 20 Specified temperature range −5 25°C Specified temperature range ±100 −0.4 +0.1 130 +IN = −IN = 12 V, VREF1 = VREF2 = 2.5 V, AD8418AWB Common mode, continuous Specified temperature range, f = dc f = dc to 10 kHz RL = 25 kΩ −2 90 +70 V dB dB VS − 0.032 V Ω pF 100 86 0.032 2 No continuous oscillation Divider to supplies Voltage applied to VREF1 and VREF2 in parallel VS = 5 V 0 0.4985 500 250 1 kHz V/μs 2.3 110 μV p-p nV/√Hz 0.032 0.5015 ±1 VS − 0.032 V/V mV/V V 2.7 5.5 V 4.1 4.2 mA mA dB +125 +150 °C °C VOUT = 0.1 V dc AD8418AWB and AD8418AB AD8418AWH 80 Operating temperature range AD8418AWB and AD8418AB AD8418AWH −40 −40 The offset adjustment is ratiometric to the power supply when VREF1 and VREF2 are used as a divider between the supplies. Rev. E | Page 3 of 18 AD8418A Data Sheet ABSOLUTE MAXIMUM RATINGS Table 3. Parameter Supply Voltage Input Voltage Range Common-Mode Differential Reverse Supply Voltage ESD Human Body Model (HBM) Operating Temperature Range AD8418AWB and AD8418AB AD8418AWH Storage Temperature Range Output Short-Circuit Duration SOIC Package θJA Thermal Resistance MSOP Package θJA Thermal Resistance Rating 6V −3 V to +80 V 5.5 V (magnitude) 0.3 V ±2000 V −40°C to +125°C −40°C to +150°C −65°C to +150°C Indefinite Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. ESD CAUTION 127.4°C/W 134.5°C/W Rev. E | Page 4 of 18 Data Sheet AD8418A 8 +IN GND 2 –IN 1 AD8418A 7 TOP VIEW (Not to Scale) VREF 1 VREF 2 3 6 VS 5 OUT NC 4 NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. 11883-002 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 2. 8-lead MSOP and 8-lead SOIC Pin Configuration Table 4. 8-lead MSOP and 8-lead SOIC Pin Function Descriptions Mnemonic −IN GND VREF2 NC OUT VS VREF1 +IN Description Negative Input. Ground. Reference Input 2. No Connect. Do not connect to this pin. Output. Supply. Reference Input 1. Positive Input. –IN 1 NC 2 GND 3 VREF2 4 NC 5 10 +IN AD8418A TOP VIEW (Not to Scale) 9 NC 8 VREF1 7 VS 6 OUT NOTES 1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. 11883-403 Pin No. 1 2 3 4 5 6 7 8 Figure 3. 10-lead MSOP Pin Configuration Table 5. 10-lead MSOP Pin Function Descriptions Pin No. 1 2, 5, 9 3 4 6 7 8 10 Mnemonic −IN NC GND VREF2 OUT VS VREF1 +IN Description Negative Input. No Connect. Do not connect to this pin. Ground. Reference Input 2. Output. Supply. Reference Input 1. Positive Input. Rev. E | Page 5 of 18 AD8418A Data Sheet 100 40 90 30 80 20 70 10 50 40 0 –10 –20 30 –30 20 –40 10 –50 0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) –60 1k 10k 100k 1M 10M FREQUENCY (Hz) 11883-006 GAIN (dB) 60 11883-003 OFFSET VOLTAGE (µV) TYPICAL PERFORMANCE CHARACTERISTICS Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p) Figure 4. Typical Offset Drift vs. Temperature 110 20 18 100 TOTAL OUTPUT ERROR (%) 16 CMRR (dB) 90 80 70 14 12 10 8 6 4 2 60 100k 1M 40 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 10 15 20 25 30 35 Figure 8. Total Output Error vs. Differential Input Voltage 400 0.5 NORMALIZED AT 25°C 0.4 BIAS CURRENT PER INPUT PIN (mA) 300 200 100 0 –100 –200 –300 VS = 5V 0.3 0.2 +IN 0.1 –IN 0 –0.1 –0.2 –0.3 –0.4 –25 –10 5 20 35 50 65 80 95 TEMPERATURE (°C) 110 125 11883-005 GAIN ERROR (µV/V) 5 DIFFERENTIAL INPUT VOLTAGE (mV) Figure 5. Typical CMRR vs. Frequency –400 –40 0 11883-007 10k 1k FREQUENCY (Hz) 11883-004 100 –2 11883-108 0 50 10 –0.5 –4 0 4 VCM (V) Figure 9. Bias Current per Input Pin vs. Common-Mode Voltage (VCM) Figure 6. Typical Gain Error vs. Temperature Rev. E | Page 6 of 18 Data Sheet AD8418A 4.5 25mV/DIV 3.5 INPUT 3.0 VS = 5V 2.5 500mV/DIV VS = 2.7V 2.0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 INPUT COMMON-MODE VOLTAGE (V) VS = 2.7V 11883-009 1.0 –5 TIME (1µs/DIV) Figure 10. Supply Current vs. Input Common-Mode Voltage 11883-012 OUTPUT 1.5 Figure 13. Fall Time (VS = 2.7 V) INPUT 50mV/DIV INPUT 25mV/DIV OUTPUT 1V/DIV 500mV/DIV TIME (1µs/DIV) VS = 5V 11883-010 VS = 2.7V TIME (1µs/DIV) Figure 11. Rise Time (VS = 2.7 V) 11883-013 OUTPUT Figure 14. Fall Time (VS = 5 V) INPUT INPUT 100mV/DIV 50mV/DIV OUTPUT OUTPUT 1V/DIV VS = 5V TIME (1µs/DIV) VS = 2.7V TIME (1µs/DIV) Figure 12. Rise Time (VS = 5 V) 11883-014 1V/DIV 11883-011 SUPPLY CURRENT (mA) 4.0 Figure 15. Differential Overload Recovery, Rising (VS = 2.7 V) Rev. E | Page 7 of 18 AD8418A Data Sheet INPUT 200mV/DIV 500mV/DIV OUTPUT OUTPUT 2V/DIV INPUT COMMON MODE VS = 5V TIME (1µs/DIV) 11883-018 11883-015 40V/DIV TIME (2µs/DIV) Figure 19. Input Common-Mode Step Response Large Scale (VS = 5 V, Inputs Shorted) Figure 16. Differential Overload Recovery, Rising (VS = 5 V) 100mV/DIV INPUT 100mV/DIV 1V/DIV OUTPUT OUTPUT INPUT COMMON MODE 11883-119 VS = 2.7V TIME (1µs/DIV) 11883-016 40V/DIV TIME (2µs/DIV) Figure 20. Input Common-Mode Step Response Small Scale (VS = 5 V, Inputs Shorted) Figure 17. Differential Overload Recovery, Falling (VS = 2.7 V) NO LOAD 330pF 470pF 1nF 200mV/DIV 100mV/DIV INPUT 2V/DIV 100mV/DIV OUTPUT 100mV/DIV TIME (1µs/DIV) 11883-120 11883-017 100mV/DIV VS = 5V TIME (4µs/DIV) Figure 21. Small Signal Response for Various Capacitive Loads Figure 18. Differential Overload Recovery, Falling (VS = 5 V) Rev. E | Page 8 of 18 Data Sheet AD8418A 0 2.7V 5V OUTPUT VOLTAGE RANGE FROM POSITIVE RAIL (mV) 40 –50 35 30 25 20 15 10 5 –150 –200 –250 –300 –350 –400 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) –500 OUTPUT VOLTAGE RANGE FROM GROUND (mV) 35 30 5V 25 2.7V 15 10 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Figure 23. Maximum Output Source Current vs. Temperature 11883-020 5 –25 2 3 4 5 6 7 8 9 10 Figure 24. Output Voltage Range from Positive Rail vs. Output Source Current 40 0 –40 1 OUTPUT SOURCE CURRENT (mA) Figure 22. Maximum Output Sink Current vs. Temperature 20 0 11883-021 –25 300 250 200 150 100 50 0 0 1 2 3 4 5 6 7 OUTPUT SINK CURRENT (mA) 8 9 10 11883-022 0 –40 MAXIMUM OUTPUT SOURCE CURRENT (mA) –100 –450 11883-019 MAXIMUM OUTPUT SINK CURRENT (mA) 45 Figure 25. Output Voltage Range from Ground vs. Output Sink Current Rev. E | Page 9 of 18 AD8418A Data Sheet –40°C +25°C +125°C 1600 1800 VS = 5.0V 1500 1400 1200 1000 HITS HITS 1200 800 600 900 600 400 –300 –200 –100 0 100 200 300 400 VOS (µV) 11883-325 0 –400 NORMALIZED AT 25°C 0.4 0.3 CMRR (µV/V) 0.2 0.1 0 –0.1 –0.2 –0.3 –25 –10 5 20 35 50 65 80 TEMPERATURE (°C) 95 110 125 11883-024 –0.4 –0.5 –40 –3 –2 –1 0 GAIN ERROR DRIFT (ppm/°C) Figure 28. Gain Error Drift Distribution Figure 26. Offset Voltage Distribution 0.5 0 Figure 27. CMRR vs. Temperature Rev. E | Page 10 of 18 1 11883-023 300 200 Data Sheet AD8418A THEORY OF OPERATION The reference inputs, VREF1 and VREF2, are tied through 100 kΩ resistors to the positive input of the main amplifier, which allows the output offset to be adjusted anywhere in the output operating range. The gain is 1 V/V from the reference pins to the output when the reference pins are used in parallel. When the pins are used to divide the supply, the gain is 0.5 V/V. The AD8418A is a single-supply, zero drift, difference amplifier that uses a unique architecture to accurately amplify small differential current shunt voltages in the presence of rapidly changing common-mode voltages. In typical applications, the AD8418A measures current by amplifying the voltage across a shunt resistor connected to its inputs by a gain of 20 V/V (see Figure 29). The AD8418A offers breakthrough performance without compromising any of the robust application needs typical of solenoid or motor control. The ability to reject PWM input common-mode voltages and the zero drift architecture providing low offset and offset drift allows the AD8418A to deliver total accuracy for these demanding applications. The AD8418A design provides excellent common-mode rejection, even with PWM common-mode inputs that can change at very fast rates, for example, 1 V/ns. The AD8418A contains proprietary technology to eliminate the negative effects of such fast changing external common-mode variations. The AD8418A features an input offset drift of less than 400 nV/°C. This performance is achieved through a novel zero drift architecture that does not compromise bandwidth, which is typically rated at 250 kHz. VCM = –2V TO +70V VS = 2.7V TO 5.5V 70V VS AD8418A VCM +IN 0V ISHUNT EMI FILTER VOUT OUT G = 20 –IN VS + RSHUNT 50A VREF 1 VS/2 EMI FILTER – ISHUNT –50A VREF2 Figure 29. Typical Application Rev. E | Page 11 of 18 11883-225 0V GND AD8418A Data Sheet OUTPUT OFFSET ADJUSTMENT UNIDIRECTIONAL OPERATION Unidirectional operation allows the AD8418A to measure currents through a resistive shunt in one direction. The basic modes for unidirectional operation are ground referenced output mode and VS referenced output mode. VS Referenced Output Mode VS referenced output 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 the wiring before power is applied to the load (see Figure 31). VS For unidirectional operation, the output can be set at the negative rail (near ground) or at the positive rail (near VS) when the differential input is 0 V. The output moves to the opposite rail when a correct polarity differential input voltage is applied. The required polarity of the differential input depends on the output voltage setting. If the output is set at the positive rail, the input polarity needs to be negative to decrease the output. If the output is set at ground, the polarity must be positive to increase the output. AD8418A R4 –IN VS + R2 VREF1 R3 VREF2 Figure 31. VS Referenced Output BIDIRECTIONAL OPERATION Bidirectional operation allows the AD8418A to measure currents through a resistive shunt in two directions. In this case, the 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 the bidirectional current is nonsymmetrical. AD8418A R4 – OUT Adjusting the output is accomplished by applying voltage(s) to the referenced inputs. VREF1 and VREF2 are tied to internal resistors that connect to an internal offset node. There is no operational difference between the pins. + +IN OUT GND When using the AD8418A in ground referenced output mode, both referenced inputs are tied to ground, which causes the output to sit at the negative rail when there are zero differential volts at the input (see Figure 30). R1 – +IN Ground Referenced Output Mode –IN R1 11883-026 The output of the AD8418A can be adjusted for unidirectional or bidirectional operation. R2 VREF1 R3 VREF2 11883-025 GND Figure 30. Ground Referenced Output Rev. E | Page 12 of 18 Data Sheet AD8418A VS EXTERNAL REFERENCED OUTPUT Tying VREF1 and VREF2 together and to a reference produces an output equal to the reference voltage when there is no differential input (see Figure 32). The output decreases with respect to the reference voltage when the input is negative, relative to the –IN pin, and increases when the input is positive, relative to the −IN pin. AD8418A R4 –IN R1 – OUT + +IN R2 VREF 1 R3 VS AD8418A 11883-028 VREF 2 GND R4 –IN R1 – Figure 33. Split Supply OUT SPLITTING AN EXTERNAL REFERENCE + +IN R2 VREF 1 R3 2.5V GND 11883-027 VREF 2 Use the internal reference resistors to divide an external reference by 2 with an accuracy of approximately 0.5%. Split an external reference by connecting one VREFx pin to ground and the other VREFx pin to the reference (see Figure 34). VS Figure 32. External Referenced Output SPLITTING THE SUPPLY AD8418A R4 –IN R1 – + +IN Rev. E | Page 13 of 18 OUT R2 VREF 1 R3 VREF 2 GND Figure 34. Split External Reference 5V 11883-029 By tying one reference pin to VS and the other to the ground pin, the output is set at half of the supply when there is no differential input (see Figure 33). The benefit of this configuration is that an external reference is not required to offset the output for bidirectional current measurement. Tying one reference pin to VS and the other to the ground pin creates a midscale offset that is ratiometric to the supply, which means that if the supply increases or decreases, 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 increases to 2.75 V. AD8418A Data Sheet APPLICATIONS INFORMATION MOTOR CONTROL 3-Phase Motor Control The AD8418A is ideally suited for monitoring current in 3-phase motor applications. The 250 kHz typical bandwidth of the AD8418A provides instantaneous current monitoring. Additionally, the typical low offset drift of 0.1 μV/°C means that the measurement error between the two motor phases is at a minimum over temperature. The AD8418A rejects PWM input common-mode voltages in the −2 V to +70 V (with a 5 V supply) range. Monitoring the current on the motor phase allows sampling of the current at any point and provides diagnostic information, such as a short to GND and battery. Refer to Figure 36 for the typical phase current measurement setup with the AD8418A. amp because ground is not typically a stable reference voltage in this type of application. The instability of the ground reference causes inaccuracies in the measurements that can be made with a simple ground referenced op amp. The AD8418A measures current in both directions as the H-bridge switches and the motor changes direction. The output of the AD8418A is configured in an external referenced bidirectional mode (see the Bidirectional Operation section). CONTROLLER 5V MOTOR VS +IN VREF 1 –IN GND VREF 2 OUT AD8418A SHUNT NC 5V 2.5V 11883-030 H-Bridge Motor Control Another typical application for the AD8418A is to form part of the control loop in H-bridge motor control. In this case, place the shunt resistor in the middle of the H-bridge to accurately measure current in both directions by using the shunt available at the motor (see Figure 35). Using an amplifier and shunt in this location is a better solution than a ground referenced op Figure 35. H-Bridge Motor Control V+ M IU IV IW V– 5V OPTIONAL DEVICE FOR OVERCURRENT PROTECTION AND FAST (DIRECT) SHUTDOWN OF POWER STAGE INTERFACE CIRCUIT AD8418A 5V AD8418A CONTROLLER BIDIRECTIONAL CURRENT MEASUREMENT REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–2V TO +70V) AMPLIFICATION HIGH OUTPUT DRIVE Figure 36. 3-Phase Motor Control Rev. E | Page 14 of 18 11883-031 AD8214 Data Sheet AD8418A 6 OUT OUTPUT 5 – AD8418A 3 6 +IN 5 4 NC 3 VREF2 2 –IN 1 NC = NO CONNECT. Figure 38. High-Side Switch High Rail Current Sensing 4 –IN 2 INDUCTIVE LOAD NC 1 –IN SWITCH VREF 2 SHUNT CLAMP DIODE 7 6 OVERCURRENT DETECTION (