High Resolution, Zero-Drift Current Shunt Monitor AD8217 High common-mode voltage range 4.5 V to 80 V operating 0 V to 85 V survival Buffered output voltage Wide operating temperature range: -40C to +125C Excellent ac and dc performance 100 nV/C typical offset drift 100 V typical offset 5 ppm/C typical gain drift 100 dB typical CMRR at dc FUNCTIONAL BLOCK DIAGRAM R4 AD8217 -IN R1 OUT +IN R2 R3 LDO 09161-001 FEATURES GND Figure 1. APPLICATIONS High side current sensing 48 V telecom Power management Base stations Unidirectional motor control Precision high voltage current sources GENERAL DESCRIPTION The AD8217 is a high voltage, high-resolution current shunt amplifier. It features a set gain of 20 V/V, with a maximum 0.35% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8217 offers excellent common-mode rejection from 4.5 V to 80 V, and includes an internal LDO, which directly powers the device from the high voltage rail. Therefore, no additional supply is necessary, provided that the input common-mode range is 4.5 V to 80 V. The AD8217 performs unidirectional current measurements across a shunt resistor in a variety of industrial and telecom applications including motor control, battery management, and base station power amplifier bias control. The AD8217 offers breakthrough performance throughout the -40C to +125C temperature range. It features a zero-drift core, which leads to a typical offset drift of 100 nV/C throughout the operating temperature and common-mode voltage range. Special attention is devoted to output linearity being maintained throughout the input differential voltage range of 0 mV to 250 mV, regardless of the common-mode voltage present, and the typical input offset voltage is 100 V. The AD8217 is offered in a 8-lead MSOP package and is specified from -40C to +125C. Rev. A 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 (c)2010-2011 Analog Devices, Inc. All rights reserved. AD8217 TABLE OF CONTENTS Features .............................................................................................. 1 Amplifier Core............................................................................ 10 Applications....................................................................................... 1 Internal LDO............................................................................... 10 Functional Block Diagram .............................................................. 1 Application Notes ........................................................................... 11 General Description ......................................................................... 1 Output Linearity......................................................................... 11 Revision History ............................................................................... 2 Applications Information .............................................................. 12 Specifications..................................................................................... 3 High-Side Current Sensing ....................................................... 12 Absolute Maximum Ratings............................................................ 4 Motor Control Current Sensing ............................................... 12 ESD Caution.................................................................................. 4 Outline Dimensions ....................................................................... 13 Pin Configuration and Function Descriptions............................. 5 Ordering Guide .......................................................................... 13 Typical Performance Characteristics ............................................. 6 Theory of Operation ...................................................................... 10 REVISION HISTORY 3/11--Rev. 0 to Rev. A Changes to Features.......................................................................... 1 Changes to Figure 18........................................................................ 8 7/10--Revision 0: Initial Version Rev. A | Page 2 of 16 AD8217 SPECIFICATIONS TOPR = -40C to +125C, TA = 25C, RL = 25 k, input common-mode voltage (VCM = 4.5 V) (RL is the output load resistor), unless otherwise noted. Table 1. Parameter GAIN Initial Accuracy Accuracy over Temperature Gain vs. Temperature VOLTAGE OFFSET Offset Voltage (RTI) 1 Over Temperature (RTI)1 Offset Drift INPUT Bias Current 2 Common-Mode Input Voltage Range Differential Input Voltage Range 3 Common-Mode Rejection (CMRR) OUTPUT Output Voltage Range Low Output Voltage Range High Output Impedance DYNAMIC RESPONSE Small Signal -3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, (RTI)1 Spectral Density, 1 kHz, (RTI)1 POWER SUPPLY Operating Range Quiescent Current Over Temperature Power Supply Rejection Ratio (PSRR) TEMPERATURE RANGE For Specified Performance Min Typ Max Unit Test Conditions/Comments V/V % % ppm/C VO 0.1 V dc, TA TOPR TOPR V V nV/C 25C TOPR TOPR 250 100 A A V mV dB TA TOPR Common-mode continuous Differential input voltage TOPR TA 4 TA4 2 V V 500 1 kHz V/s 2.3 110 V p-p nV/Hz 20 0.1 0.35 5 250 300 100 500 800 80 4.5 90 0.01 5 4.5 90 -40 80 800 V A dB +125 C 110 1 Power regulated from common mode Throughout input common mode TOPR RTI = referred to input. Refer to Figure 8 for further information on the input bias current. This current varies based on the input common-mode voltage. Additionally, the input bias current flowing to the +IN pin is also the supply current to the internal LDO. 3 The differential input voltage is specified as 250 mV typical because the output is internally clamped to 5 V. This ensures the output voltage does not exceed 5 V and can interface and not cause damage to any typical converter, regardless of the high voltage present at the inputs of the AD8217 (up to 80 V). 4 See Figure 17 and Figure 18 for further information on the output range of the AD8217 with various loads. The AD8217 output clamps to a maximum voltage of 5.6 V when the voltage at pin +IN is greater than 5.6 V. When the voltage at +IN is less than 5.6 V, the output reaches a maximum value of (V+IN - 100 mV). 2 Rev. A | Page 3 of 16 AD8217 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Maximum Input Voltage ( +IN, -IN to GND) Differential Input Voltage (+IN to -IN) HBM (Human Body Model) ESD Rating Operating Temperature Range (TOPR) Storage Temperature Range Output Short-Circuit Duration Rating 0 V to 85 V 1 V 2000 V -40C to +125C -65C to +150C Indefinite Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION Rev. A | Page 4 of 16 AD8217 +IN 1 NC 2 AD8217 NC 3 TOP VIEW (Not to Scale) GND 4 8 -IN 7 NC 6 NC 5 OUT NC = NO CONNECT 09161-002 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic +IN NC NC GND OUT NC NC -IN Description Noninverting Input. Supply pin to the internal LDO. No Connect. No internal connection to pin. No Connect. No internal connection to pin. Ground. Output. No Connect. No internal connection to pin. No Connect. No internal connection to pin. Inverting Input. Rev. A | Page 5 of 16 AD8217 TYPICAL PERFORMANCE CHARACTERISTICS 30 40 27 38 24 36 MAGNITUDE (dB) 21 VOSI (V) 34 32 30 18 15 12 9 28 6 26 0 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 1k Figure 3. Typical Input Offset vs. Temperature 10k 100k FREQUENCY (Hz) 1M 09161-006 3 09161-003 24 -40 Figure 6. Typical Small-Signal Bandwidth (VOUT = 200 mV p-p) 10 140 9 130 8 TOTAL OUTPUT ERROR (%) 120 CMRR (dB) 110 100 90 -40C +25C +125C 80 70 7 6 5 4 3 2 1 0 -1 -2 -3 60 -5 10k 100k 1M FREQUENCY (Hz) 0 09161-004 1000 Figure 4. Typical CMRR vs. Frequency 450 700 INPUT BIAS CURRENT (A) 800 400 350 300 250 200 15 20 25 30 35 DIFFERENTIAL INPUT (mV) 40 45 50 +IN 600 500 400 300 200 100 150 -20 0 20 40 60 TEMPERATURE (C) 80 100 120 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 INPUT COMMON-MODE VOLTAGE (V) Figure 5. Typical Gain Error vs. Temperature Figure 8. Input Bias Current vs. Input Common-Mode Voltage (Differential Input Voltage = 5 mV) Rev. A | Page 6 of 16 09161-008 -IN 0 09161-005 GAIN ERROR (ppm) 10 Figure 7. Total Output Error vs. Differential Input Voltage 500 100 -40 5 09161-007 -4 50 100 AD8217 INPUT 100mV/DIV INPUT 5mV/DIV OUTPUT 2V/DIV 1s/DIV 5s/DIV Figure 9. Rise Time (Differential Input = 5 mV) 09161-012 100mV/DIV 09161-009 OUTPUT Figure 12. Fall Time (Differential Input = 200 mV) INPUT 200mV/DIV INPUT OUTPUT 2V/DIV 2V/DIV 5s/DIV 09161-010 OUTPUT 5s/DIV Figure 10. Rise Time (Differential Input = 200 mV) 09161-013 100mV/DIV Figure 13. Differential Overload Recovery, Rising INPUT INPUT 5mV/DIV 200mV/DIV OUTPUT OUTPUT 100mV/DIV 5s/DIV Figure 11. Fall Time (Differential Input = 5 mV) Figure 14. Differential Overload Recovery, Falling Rev. A | Page 7 of 16 09161-014 1s/DIV 09161-011 2V/DIV AD8217 250 MAXIMUM OUTPUT SINK CURRENT (mA) 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 0 10 20 30 40 50 60 70 80 90 100 110 120 TEMPERATURE (C) 150 100 50 0 09161-015 5.0 -40 -30 -20 -10 200 0 Figure 15. Maximum Output Sink Current vs. Temperature 0.5 1.0 1.5 2.0 2.5 3.0 3.5 OUTPUT SINK CURRENT (mA) 4.0 4.5 5.0 Figure 18. Output Voltage Range From GND vs. Output Sink Current 9.0 8.5 INPUT 8.0 50V/DIV 7.5 7.0 6.5 OUTPUT 6.0 1V/DIV 5.5 5.0 4.5 150 TEMPERATURE (C) 500ns/DIV 09161-016 140 130 110 120 90 100 80 70 60 50 40 30 20 0 10 -10 -20 -30 -40 4.0 09161-019 MAXIMUM OUTPUT SOURCE CURRENT (mA) 9.5 Figure 19. Common-Mode Step Response, Rising Figure 16. Maximum Output Source Current vs. Temperature 5.000 4.990 INPUT 4.980 50V/DIV 4.970 OUTPUT 4.960 1V/DIV 4.950 4.940 4.930 4.910 4.900 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT SOURCE CURRENT (mA) 4.5 5.0 Figure 17. Output Voltage Range vs. Output Source Current 1s/DIV Figure 20. Common-Mode Step Response (Falling) Rev. A | Page 8 of 16 09161-020 4.920 09161-017 OUTPUT VOLTAGE SWING FROM RAIL (V) 5.010 0 09161-018 OUTPUT VOLTAGE RANGE FROM GND (mV) 12.0 AD8217 1200 700 1000 600 500 800 COUNT COUNT 800 600 400 300 400 200 -150 -100 -50 0 50 100 150 100 0 200 VOSI (V) 600 400 200 09161-022 COUNT 800 0 GAIN DRIFT (ppm/C) -0.2 0 0.2 Figure 23. Input Offset Drift Distribution 1000 -5 -0.4 OFFSET DRIFT (V/C) Figure 21. Input Offset Distribution 0 -10 09161-023 0 -200 09161-021 200 5 10 Figure 22. Gain Drift Distribution Rev. A | Page 9 of 16 0.4 AD8217 THEORY OF OPERATION AMPLIFIER CORE In typical applications, the AD8217 amplifies a small differential input voltage generated by the load current flowing through a shunt resistor. The AD8217 rejects high common-mode voltages (up to 80 V) and provides a ground-referenced, buffered output that interfaces with an analog-to-digital converter (ADC). Figure 24 shows a simplified schematic of the AD8217. R4 AD8217 ILOAD -IN R1 V2 SHUNT +IN V1 4.5V TO 80V OUT R2 R3 LDO GND Figure 24. Simplified Schematic The AD8217 is configured as a difference amplifier. The transfer function is OUT = (R4/R1) x (V1 - V2) Resistors R4 and R1 are matched to within 0.01% and have values of 1.5 M and 75 k, respectively, meaning an input to output total gain of 20 V/V for the AD8217. 09161-024 LOAD The AD8217 accurately amplifies the input differential signal, rejecting high voltage common modes ranging from 4.5 V to 80 V. The main amplifier uses a novel zero-drift architecture, providing the end user with an extremely stable part over temperature. The offset drift is typically less than 100 nV/C. This performance leads to optimal accuracy and dynamic range. INTERNAL LDO The AD8217 includes an internal LDO, which allows the device to power directly from the common-mode voltage at the inputs. No additional standalone supply is necessary, provided that the common-mode voltage at the +IN pin is at least 4.5 V and up to 80 V. Once the common-mode voltage is above 5.6 V, the LDO output reaches its maximum value, that is 5.6 V. This is also the maximum output voltage range of the AD8217. Because the AD8217 output typically interfaces with a converter, the 5.6 V maximum output range ensures the ADC input is not damaged due to excessive overvoltage. The input bias current flowing through Pin +IN powers the internal LDO and, therefore, doubles as the supply current for the AD8217. This current varies depending on the input common-mode voltage. See Figure 8 for additional information. Rev. A | Page 10 of 16 AD8217 APPLICATION NOTES OUTPUT LINEARITY In all current sensing applications where the common-mode voltage can vary significantly, it is important that the current sensor maintain the specified output linearity, regardless of the input differential or common-mode voltage. The AD8217 maintains a very high input-to-output linearity even when the differential input voltage is very small. Regardless of the common mode, the AD8217 provides a correct output voltage when the input differential is at least 1 mV. The ability of the AD8217 to work with very small differential inputs, regardless of the common-mode voltage, allows for optimal dynamic range, accuracy, and flexibility in any current sensing application. 200 180 160 OUTPUT (mV) 140 120 100 80 60 40 0 0 1 2 3 4 5 6 7 DIFFERENTIAL INPUT (mV) 8 9 10 09161-025 20 Figure 25. Gain Linearity at Small Differential Inputs (VCM = 4.5 V to 80 V) Rev. A | Page 11 of 16 AD8217 APPLICATIONS INFORMATION HIGH-SIDE CURRENT SENSING MOTOR CONTROL CURRENT SENSING In this configuration, the shunt resistor is referenced to the battery (see Figure 26). High voltage is present at the inputs of the current sense amplifier. When the shunt is battery referenced, the AD8217 produces a linear ground-referenced analog output. The AD8217 includes an internal LDO, which allows the part to be powered from the high voltage rail, with no need for an additional standalone supply. The AD8217 is a practical, accurate solution for high-side current sensing in motor control applications. In cases where the shunt resistor is referenced to battery and the current flowing is unidirectional (as shown in Figure 27), the AD8217 monitors the current with no additional supply pin necessary. BATTERY IMOTOR ILOAD 4.5V TO 80V SHUNT ADC -IN +IN MOTOR -IN +IN AD8217 AD8217 09161-026 GND GND 09161-027 OUT OUT Figure 27. High-Side Current Sensing in Motor Control Figure 26. Battery-Referenced Shunt Resistor Rev. A | Page 12 of 16 AD8217 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15 MAX 1.10 MAX 0.40 0.25 6 0 0.23 0.09 0.80 0.55 0.40 COMPLIANT TO JEDEC STANDARDS MO-187-AA 100709-B 0.15 0.05 COPLANARITY 0.10 Figure 28. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD8217BRMZ AD8217BRMZ-RL AD8217BRMZ-R7 1 Temperature Range -40C to +125C -40C to +125C -40C to +125C Package Description 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) Z = RoHS Compliant Part. Rev. A | Page 13 of 16 Package Option RM-8 RM-8 RM-8 Branding Y2L Y2L Y2L AD8217 NOTES Rev. A | Page 14 of 16 AD8217 NOTES Rev. A | Page 15 of 16 AD8217 NOTES (c)2010-2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09161-0-3/11(A) Rev. A | Page 16 of 16