AD8219

Zero Drift, Unidirectional Current Shunt Monitor AD8219 FEATURES High common-mode voltage range 4 V to 80 V operating −0.3 V to +85 V survival Buffered output voltage Gain = 60 V/V Wide operating temperature range: −40°C to +125°C Excellent ac and dc performance ±100 nV/°C typical offset drift ±50 µV/°C typical offset ±5 ppm/°C typical gain drift 110 dB typical CMRR at dc FUNCTIONAL BLOCK DIAGRAM VS R4 LDO –IN +IN R2 R3 09415-001 R1 OUT AD8219 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 AD8219 is a high voltage, high resolution, current shunt amplifier. It features a set gain of 60 V/V, with a maximum ±0.3% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8219 offers excellent input common-mode rejection from 4 V to 80 V. The AD8219 performs unidirectional current measurements across a shunt resistor in a variety of industrial and telecom applications including motor control, power management, and base station power amplifier bias control. The AD8219 offers breakthrough performance throughout the −40°C to +125°C 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, regardless of the common-mode voltage present, while the typical input offset voltage is ±50 µV. The AD8219 is offered in a 8-lead MSOP package. 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 ©2011 Analog Devices, Inc. All rights reserved. AD8219 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 Amplifier Core ............................................................................ 10 Supply Connections ................................................................... 10 Output Clamping ....................................................................... 10 Application Information ................................................................ 11 Output Linearity ......................................................................... 11 Applications Information .............................................................. 12 High-Side Current Sensing ....................................................... 12 Motor Control Current Sensing ............................................... 12 Outline Dimensions ....................................................................... 13 Ordering Guide .......................................................................... 13 REVISION HISTORY 1/11—Revision 0: Initial Version Rev. 0 | Page 2 of 16 AD8219 SPECIFICATIONS TOPR = −40°C to +125°C, TA = 25°C, RL = 25 kΩ, input common-mode voltage (VCM) = 4 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 (RTI1) Offset Drift INPUT Bias Current2 Common-Mode Input Voltage Range Differential Input Voltage Range3 Common-Mode Rejection (CMRR) OUTPUT Output Voltage Range Low4 Output Voltage Range High4 Output Impedance DYNAMIC RESPONSE Small Signal −3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, (RTI1) Spectral Density, 1 kHz, (RTI1) POWER SUPPLY Operating Range Quiescent Current Over Temperature5 Power Supply Rejection Ratio (PSRR) TEMPERATURE RANGE For Specified Performance 1 2 Min Typ 60 ±0.1 Max Unit V/V % % ppm/°C µV µV nV/°C µA µA V mV dB V V Ω kHz V/µs µV p-p nV/√Hz Test Conditions/Comments ±0.3 ±5 ±200 ±300 ±100 130 4 0 94 0.01 VS − 0.1 2 500 1 2.3 110 4 100 −40 110 +125 80 800 220 80 83 110 VO ≥ 0.1 V dc, TA TOPR TOPR 25°C TOPR TOPR TA, input common mode = 4 V, VS = 4 V TOPR Common-mode continuous Differential input voltage TOPR TA TA V µA dB °C VS input range 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 83 mV maximum because the output is internally clamped to 5.6 V. See the Output Clamping section. 4 See Figure 19 and Figure 20 for further information on the output range of the AD8219 with various loads. The AD8219 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 (VS − 100 mV). 5 VS (Pin 2) can be connected to a separate supply ranging from 4 V to 80 V, or it can be connected to the positive input pin (+IN) of the AD8219. In this mode, the current drawn varies with increasing voltage. See Figure 9. Rev. 0 | Page 3 of 16 AD8219 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Maximum Input Voltage ( +IN, −IN to GND) Differential Input Voltage (+IN to –IN) Human Body Model (HBM) ESD Rating Operating Temperature Range (TOPR) Storage Temperature Range Output Short-Circuit Duration Rating −0.3 V to +85 V ±5 V ±1000 V −40°C to +125°C −65°C to +150°C 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. 0 | Page 4 of 16 AD8219 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS +IN 1 VS 2 NC 3 GND 4 8 –IN NC NC OUT 09415-002 AD8219 TOP VIEW (Not to Scale) 7 6 5 NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic +IN VS NC GND OUT NC NC −IN Description Noninverting Input. Supply Pin. Bypass with a standard 0.1 μF capacitor. Do Not Connect to This Pin. Ground. Output. Do Not Connect to This Pin. Do Not Connect to This Pin. Inverting Input. Rev. 0 | Page 5 of 16 AD8219 TYPICAL PERFORMANCE CHARACTERISTICS –19.0 –19.5 –20.0 20 –20.5 40 30 MAGNITUDE (dB) 09415-121 VOS (µV) –21.0 –21.5 –22.0 –22.5 10 0 –10 –20 –23.0 –23.5 –24.0 –40 –30 –40 1k –20 0 20 40 60 80 100 120 140 10k 100k FREQUENCY (Hz) 1M 10M TEMPERATURE (°C) Figure 3. Typical Input Offset vs. Temperature Figure 6. Typical Small Signal Bandwidth (VOUT = 200 mV p-p) 120 110 7 6 TYPICAL OUTPUT ERROR (%) 5 4 3 2 1 0 –1 100 CMRR (dB) 90 80 70 60 50 100 1k 10k FREQUENCY (Hz) 100k 1M 09415-104 0 1 2 3 4 5 6 7 8 9 10 DIFFERENTIAL INPUT VOLTAGE (mV) Figure 4. Typical CMRR vs. Frequency Figure 7. Typical Output Error vs. Differential Input Voltage 0 –50 –100 300 250 INPUT BIAS CURRENT (µA) GAIN ERROR (ppm) –150 –200 –250 –300 –350 –400 –450 09415-120 +IN 200 150 100 50 –IN –20 0 20 40 60 80 100 120 140 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 INPUT COMMON-MODE VOLTAGE (V) TEMPERATURE (°C) Figure 5. Typical Gain Error vs. Temperature Figure 8. Input Bias Current vs. Input Common-Mode Voltage (Differential Input Voltage = 5 mV) (VS = 5 V) Rev. 0 | Page 6 of 16 09415-101 –500 –40 0 09415-128 –2 09415-105 AD8219 550 500 SUPPLY CURRENT (µA) VCM = 5V 450 VCM = 80V 400 INPUT 50mV/DIV 350 OUTPUT 2V/DIV 09415-110 09415-112 09415-111 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 SUPPLY VOLTAGE (V) 09415-102 300 5µs/DIV Figure 9. Typical Supply Current vs. Supply Voltage (VS Connected to +IN) 550 500 Figure 12. Rise Time (Differential Input = 50 mV) SUPPLY CURRENT (µA) 450 400 350 300 250 200 –40 INPUT 5mV/DIV OUTPUT 200mV/DIV –20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) 09415-103 1µs/DIV Figure 10. Typical Supply Current Change over Temperature (VS = 5 V) Figure 13. Fall Time (Differential Input = 5 mV) INPUT 50mV/DIV INPUT 5mV/DIV OUTPUT 2V/DIV OUTPUT 200mV/DIV 09415-109 1µs/DIV 5µs/DIV Figure 11. Rise Time (Differential Input = 5 mV) Figure 14. Fall Time (Differential Input = 50 mV) Rev. 0 | Page 7 of 16 AD8219 7.0 INPUT 100mV/DIV MAXIMUM OUTPUT SOURCE CURRENT (mA) 09415-113 6.5 6.0 OUTPUT 2V/DIV 5.5 5.0 4.5 –20 0 20 40 60 80 100 120 5µs/DIV TEMPERATURE (°C) Figure 15. Differential Overload Recovery, Falling Figure 18. Maximum Output Source Current vs. Temperature 5.0 4.8 4.5 4.3 4.0 3.8 3.5 3.3 09415-114 +125°C +25°C –40°C INPUT 100mV/DIV OUTPUT 2V/DIV OUTPUT VOLTAGE FROM RAIL (V) 0 0.5 1.0 1.5 2.0 2.5 3.0 5µs/DIV SOURCE CURRENT (mA) Figure 16. Differential Overload Recovery, Rising 12 Figure 19. Output Voltage Range vs. Output Source Current (VS = 5 V) 0.40 MAXIMUM OUTPUT SINK CURRENT (mA) OUTPUT VOLTAGE FROM GROUND (V) 11 10 9 8 7 6 5 –40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 0 0.5 1.0 1.5 2.0 2.5 3.0 +125°C +25°C –40°C 09415-107 –20 0 20 40 60 80 100 120 3.5 4.0 TEMPERATURE (°C) SINK CURRENT (mA) Figure 17. Maximum Output Sink Current vs. Temperature Figure 20. Output Voltage Range From Ground vs. Output Sink Current (VS = 5 V) Rev. 0 | Page 8 of 16 09415-129 09415-106 3.0 09415-108 4.0 –40 AD8219 70 60 50 INPUT COMMON MODE 50V/DIV COUNT OUTPUT 200mV/DIV 40 30 20 10 0 –6 09415-115 –4 –2 0 2 4 6 2µs/DIV GAIN DRIFT (ppm/°C) Figure 21. Common-Mode Step Response (Falling) 35 30 25 INPUT COMMON MODE 50V/DIV Figure 24. Gain Drift Distribution COUNT 20 15 10 OUTPUT 200mV/DIV 5 0 –0.6 09415-116 –0.4 –0.2 0 0.2 0.4 0.6 1µs/DIV OFFSET DRIFT (µV/°C) Figure 22. Common-Mode Step Response (Rising) Figure 25. Input Offset Drift Distribution 50 40 COUNT 30 20 10 –100 –50 0 VOSI (µV) 50 100 150 Figure 23. Input Offset Distribution 09415-118 0 –150 Rev. 0 | Page 9 of 16 09415-117 09415-119 AD8219 THEORY OF OPERATION AMPLIFIER CORE In typical applications, the AD8219 amplifies a small differential input voltage generated by the load current flowing through a shunt resistor. The AD8219 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 26 shows a simplified schematic of the AD8219. 4V TO 80V VS GND R4 ILOAD V2 LOAD V1 4V TO 80V SHUNT –IN +IN R2 R3 09415-024 The AD8219 accurately amplifies the input differential signal, rejecting high voltage common modes ranging from 4 V to 80 V. The main amplifier uses a novel zero drift architecture, providing the end user with breakthrough temperature stability. The offset drift is typically less than ±100 nV/°C. This performance leads to optimal accuracy and dynamic range. SUPPLY CONNECTIONS The AD8219 includes an internal LDO, which allows the user to connect the VS pin to the inputs, or use a separate supply at Pin 2 (VS) to power the device. The input range of the supply pin is equivalent to the input common-mode range of 4 V to 80 V. The user must ensure that VS is always connected to the +IN pin or a separate low impedance supply, which can range from 4 V to 80 V. The VS pin should not be floating. LDO R1 OUT AD8219 GND OUTPUT CLAMPING When the input common-mode voltage in the application is above 5.6 V, the internal LDO output of the AD8219 also reaches its maximum value of 5.6 V, which is the maximum output range of the AD8219. Because in typical applications the output interfaces with a converter, clamping the AD8219 output voltage to 5.6 V ensures the ADC input is not damaged due to excessive overvoltage. Figure 26. Simplified Schematic The AD8219 is configured as a difference amplifier. The transfer function is OUT = (R4/R1) × (V1 − V2) Resistors R4 and R1 are matched to within 0.01% and have values of 1.5 MΩ and 25 kΩ, respectively, meaning an input to output total gain of 60 V/V for the AD8219, while the difference at V1 and V2 is the voltage across the shunt resistor or VIN. Therefore, the input-to-output transfer function for the AD8219 is OUT = (20) × (VIN) Rev. 0 | Page 10 of 16 AD8219 APPLICATION INFORMATION 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 AD8219 maintains a very high input-to-output linearity even when the differential input voltage is very small. 0.7 0.6 Regardless of the common mode, the AD8219 provides a correct output voltage when the input differential is at least 1 mV. The ability of the AD8219 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. OUTPUT VOLTAGE (V) 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 6 7 8 9 10 DIFFERENTIAL INPUT VOLTAGE (mV) Figure 27. Typical Gain Linearity at Small Differential Inputs (VCM = 4 V to 80 V) 09415-127 Rev. 0 | Page 11 of 16 AD8219 APPLICATIONS INFORMATION HIGH-SIDE CURRENT SENSING In this configuration, the shunt resistor is referenced to the battery (see Figure 28). High voltage is present at the inputs of the current sense amplifier. When the shunt is battery referenced, the AD8219 produces a linear ground referenced analog output. ILOAD 4V TO 80V SHUNT +IN –IN MOTOR CONTROL CURRENT SENSING The AD8219 is a practical, accurate solution for high-side current sensing in motor control applications. In cases where the shunt resistor is referenced to a battery and the current flowing is unidirectional (as shown in Figure 30), the AD8219 monitors the current with no additional supply pin necessary provided the battery voltage in the following circuit is in the 4 V to 80 V range. BATTERY IMOTOR LOAD AD8219 VS GND OUT 09415-026 +IN –IN MOTOR AD8219 VS GND OUT 09415-027 Figure 28. Battery Referenced Shunt Resistor Figure 28 shows the supply pin, VS, connected directly to the positive input (+IN) pin. In this mode, the internal LDO powers the AD8219 as long as the common-mode voltage at the input pins is 4 V to 80 V. Additionally, VS can also be connected to a standalone supply that can vary from 4 V to 80 V as shown in Figure 29. ILOAD 4V TO 80V SHUNT +IN –IN Figure 30. High-Side Current Sensing in Motor Control LOAD AD8219 09415-029 4V TO 80V VS GND OUT Figure 29. Standalone Supply Operation Rev. 0 | Page 12 of 16 AD8219 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 5 3.20 3.00 2.80 PIN 1 IDENTIFIER 1 5.15 4.90 4.65 4 0.65 BSC 0.95 0.85 0.75 0.15 0.05 COPLANARITY 0.10 0.40 0.25 15° MAX 1.10 MAX 0.80 0.55 0.40 10-07-2009-B 6° 0° 0.23 0.09 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 31. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model1 AD8219BRMZ AD8219BRMZ-RL 1 Temperature Range −40°C to +125°C −40°C to +125°C Package Description 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP] Package Option RM-8 RM-8 Branding Y3S Y3S Z = RoHS Compliant Part. Rev. 0 | Page 13 of 16 AD8219 NOTES Rev. 0 | Page 14 of 16 AD8219 NOTES Rev. 0 | Page 15 of 16 AD8219 NOTES ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09415-0-1/11(0) Rev. 0 | Page 16 of 16