High Common-Mode Voltage, Difference Amplifier AD629 FUNCTIONAL BLOCK DIAGRAM Improved replacement for: INA117P and INA117KU ±270 V common-mode voltage range Input protection to ±500 V common mode ±500 V differential mode Wide power supply range (±2.5 V to ±18 V) ±10 V output swing on ±12 V supply 1 mA maximum power supply current REF(–) 1 –IN 2 +IN 3 –VS 4 380kΩ 21.1kΩ 380kΩ 380kΩ 20kΩ AD629 8 NC 7 +VS 6 OUTPUT 5 REF(+) 00783-001 FEATURES NC = NO CONNECT Figure 1. GENERAL DESCRIPTION HIGH ACCURACY DC PERFORMANCE 3 ppm maximum gain nonlinearity (AD629B) 20 μV/°C maximum offset drift (AD629A) 10 μV/°C maximum offset drift (AD629B) 10 ppm/°C maximum gain drift The AD629 is a difference amplifier with a very high input, common-mode voltage range. It is a precision device that allows the user to accurately measure differential signals in the presence of high common-mode voltages up to ±270 V. The AD629 can replace costly isolation amplifiers in applications that do not require galvanic isolation. The device operates over a ±270 V common-mode voltage range and has inputs that are protected from common-mode or differential mode transients up to ±500 V. EXCELLENT AC SPECIFICATIONS 77 dB minimum CMRR @ 500 Hz (AD629A) 86 dB minimum CMRR @ 500 Hz (AD629B) 500 kHz bandwidth The AD629 has low offset, low offset drift, low gain error drift, low common-mode rejection drift, and excellent CMRR over a wide frequency range. APPLICATIONS High voltage current sensing Battery cell voltage monitors Power supply current monitors Motor controls Isolation The AD629 is available in die and packaged form featuring 8-lead PDIP and 8-lead SOIC packages. For all packages (including die) and grades, performance is guaranteed over the industrial temperature range of −40°C to +85°C. 2mV/DIV 95 OUTPUT ERROR (2mV/DIV) 90 85 80 75 70 65 55 50 20 100 1k FREQUENCY (Hz) 10k 20k 00783-003 60 00783-002 COMMON-MODE REJECTION RATIO (dB) 100 60V/DIV –240 –120 0 120 COMMON-MODE VOLTAGE (V) 240 Figure 2. Common-Mode Rejection Ratio vs. Frequency Figure 3. Error Voltage vs. Input Common-Mode Voltage 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 ©1999-2011 Analog Devices, Inc. All rights reserved. Rev. C AD629 TABLE OF CONTENTS Features .............................................................................................. 1 Basic Connections...................................................................... 11 Applications....................................................................................... 1 Single-Supply Operation ........................................................... 11 Functional Block Diagram .............................................................. 1 System-Level Decoupling and Grounding.............................. 11 General Description ......................................................................... 1 Using a Large Sense Resistor..................................................... 12 Revision History ............................................................................... 2 Output Filtering.......................................................................... 12 Specifications..................................................................................... 3 Output Current and Buffering.................................................. 13 Absolute Maximum Ratings............................................................ 4 A Gain of 19 Differential Amplifier......................................... 13 ESD Caution.................................................................................. 4 Error Budget Analysis Example 1 ............................................ 13 Pin Configuration and Function Descriptions............................. 5 Error Budget Analysis Example 2 ............................................ 14 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 15 Theory of Operation ...................................................................... 10 Ordering Guide .......................................................................... 16 Applications..................................................................................... 11 REVISION HISTORY 4/11—Rev. B to Rev. C Changes to General Description Section ...................................... 1 Added Endnote 1 in Table 1............................................................ 3 Added Figure 5; Renumbered Sequentially .................................. 4 Added Table 3; Renumbered Sequentially .................................... 4 Added Pin Configuration and Function Descriptions Section, Figure 6, and Table 4 ........................................................................ 5 Changes to Ordering Guide .......................................................... 16 3/07—Rev. A to Rev. B Updated Format and Layout .............................................Universal Changes to Ordering Guide .......................................................... 15 3/00—Rev. 0 to Rev. A 10/99—Revision 0: Initial Version Rev. C | Page 2 of 16 AD629 SPECIFICATIONS TA = 25°C, VS = ±15 V, unless otherwise noted. Table 1. Parameter GAIN Nominal Gain Gain Error Gain Nonlinearity Gain vs. Temperature OFFSET VOLTAGE Offset Voltage vs. Temperature vs. Supply (PSRR) INPUT Common-Mode Rejection Ratio Operating Voltage Range Input Operating Impedance OUTPUT Operating Voltage Range Output Short-Circuit Current Capacitive Load DYNAMIC RESPONSE Small Signal –3 dB Bandwidth Slew Rate Full Power Bandwidth Settling Time OUTPUT NOISE VOLTAGE 0.01 Hz to 10 Hz Spectral Density, ≥100 Hz 2 POWER SUPPLY Operating Voltage Range Quiescent Current TEMPERATURE RANGE For Specified Performance 1 2 Condition VOUT = ±10 V, RL = 2 kΩ Min RL = 10 kΩ TA = TMIN to TMAX VS = ±5 V TA = TMIN to TMAX VS = ±5 V to ± 15 V 84 VCM = ±250 V dc TA = TMIN to TMAX VCM = 500 V p-p, dc to 500 Hz VCM = 500 V p-p, dc to 1 kHz Common mode Differential Common mode Differential 77 73 77 RL = 10 kΩ RL = 2 kΩ VS = ±12 V, RL = 2 kΩ ±13 ±12.5 ±10 AD629A 1 Typ Max Min 1 0.01 4 1 3 10 1 0.01 4 1 3 0.2 1 0.1 6 100 20 0.05 10 90 88 86 82 86 88 96 ±270 ±13 ±13 ±12.5 ±10 1000 500 2.1 28 15 12 5 1.7 ±2.5 0.9 1.2 −40 ±18 1 ±2.5 +85 −40 Specifications for the AD629 A grade are also valid for the die model (listed in the Ordering Guide as AD629AC-WP). See Figure 21. Rev. C | Page 3 of 16 Unit V/V % ppm ppm ppm/°C mV mV μV/°C dB dB dB dB dB V V kΩ kΩ V V V mA pF ±25 15 550 VOUT = 0 V TMIN to TMAX 0.5 1 10 200 800 1000 VOUT = 20 V p-p 0.01%, VOUT = 10 V step 0.1%, VOUT = 10 V step 0.01%, VCM = 10 V step, VDIFF = 0 V 0.03 10 3 10 90 200 800 1.7 TA = TMIN to TMAX 3 110 ±270 ±13 ±25 Stable operation AD629B Typ Max 500 2.1 28 15 12 5 kHz V/μs kHz μs μs μs 15 550 μV p-p nV/√Hz 0.9 1.2 ±18 1 V mA mA +85 °C AD629 ABSOLUTE MAXIMUM RATINGS Table 2. 1a 1 Rating ±18 V 2 7 See Figure 4 See Figure 4 ±300 V ±500 V Indefinite –VS − 0.3 V to +VS + 0.3 V 150°C −55°C to +125°C −65°C to +150°C 300°C Y 3 4 6b 6a 5a 5b X Specification is for device in free air: 8-Lead PDIP, θJA = 100°C/W; 8-Lead SOIC, θJA = 155°C/W. DIE SIZE: 1655µm (X) by 2465µm (Y) Figure 5. Metallization Photograph 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. 2.0 TJ = 150°C 8-LEAD PDIP 1.5 Table 3. Pin Pad Coordinates Coordinates1 X Y −677 +1082 −534 +1084 Pad 1a 1b Pin REF(−) 2 3 4 5a 5b −IN +IN −VS REF(+) −661 −661 +680 +396 +538 +939 −658 −800 −1084 −1084 6a 6b OUTPUT +681 +681 −950 −807 7 +VS +680 +612 1.0 8-LEAD SOIC 0.5 0 –50 –40 –30 –20 –10 0 10 20 30 40 50 60 AMBIENT TEMPERATURE (°C) 00783-004 MAXIMUM POWER DISSIPATION (W) 1b 00783-041 Parameter Supply Voltage, VS Internal Power Dissipation1 8-Lead PDIP (N) 8-Lead SOIC (R) Input Voltage Range, Continuous Common-Mode and Differential, 10 sec Output Short-Circuit Duration Pin 1 and Pin 5 Maximum Junction Temperature Operating Temperature Range Storage Temperature Range Lead Temperature (Soldering 60 sec) 70 80 90 1 Figure 4. Maximum Power Dissipation vs. Temperature for SOIC and PDIP Description For the die model, either pad can be bonded because 1a and 1b are internally shorted. For the die model, either pad can be bonded because 5a and 5b are internally shorted. For the die model, both pads must be bonded because 6a and 6b are not internally shorted. All coordinates are with respect to the center of the die. ESD CAUTION Rev. C | Page 4 of 16 AD629 REF(–) 1 8 NC –IN 2 AD629 7 +VS +IN 3 TOP VIEW (Not to Scale) 6 OUTPUT 5 REF(+) –VS 4 NC = NO CONNECT Figure 6. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic REF(−) −IN +IN −VS REF(+) OUTPUT +VS NC Description Negative Reference Voltage Input. Inverting Input. Noninverting Input. Negative Supply Voltage. Positive Reference Voltage Input. Output. Positive Supply Voltage. No Connect. Do not connect to this pin. Rev. C | Page 5 of 16 00783-040 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS AD629 TYPICAL PERFORMANCE CHARACTERISTICS 100 400 90 360 80 320 COMMON-MODE VOLTAGE (±V) 60 50 40 30 10 0 100 1k 10k 100k FREQUENCY (Hz) 1M 120 80 0 10M 2 4 6 8 10 12 14 16 POWER SUPPLY VOLTAGE (±V) 18 20 RL = 2kΩ VS = ±18V OUTPUT ERROR (2mV/DIV) VS = ±15V 4V/DIV VS = ±10V –8 –4 0 4 VOUT (V) 8 12 16 VS = ±15V VS = ±12V 00783-007 VS = ±12V –12 0 Figure 10. Common-Mode Operating Range vs. Power Supply Voltage VS = ±18V OUTPUT ERROR (2mV/DIV) 160 RL = 10kΩ 2mV/DIV –16 TA = –40°C 200 40 Figure 7. Common-Mode Rejection Ratio vs. Frequency –20 TA = +85°C 240 00783-006 20 280 00783-009 70 TA = +25°C VS = ±10V –20 20 Figure 8. Typical Gain Error Normalized @ VOUT = 0 V and Output Voltage Operating Range vs. Supply Voltage, RL = 10 kΩ (Curves Offset for Clarity) –16 –12 –8 –4 4V/DIV 0 4 VOUT (V) 8 12 16 00783-010 COMMON-MODE REJECTION RATIO (dB) TA = 25°C, VS = ±15 V, unless otherwise noted. 20 Figure 11. Typical Gain Error Normalized @ VOUT = 0 V and Output Voltage Operating Range vs. Supply Voltage, RL = 2 kΩ (Curves Offset for Clarity) RL = 1kΩ VS = ±5V, RL = 10kΩ OUTPUT ERROR (2mV/DIV) VS = ±15V VS = ±10V –20 –16 –12 –8 –4 4V/DIV 0 4 VOUT (V) 8 12 16 VS = ±5V, RL = 1kΩ 00783-008 VS = ±12V VS = ±5V, RL = 2kΩ 1V/DIV VS = ±2.5V, RL = 1kΩ –20 20 Figure 9. Typical Gain Error Normalized @ VOUT = 0 V and Output Voltage Operating Range vs. Supply Voltage, RL = 1 kΩ (Curves Offset for Clarity) –16 –12 –8 –4 0 4 VOUT (V) 8 12 16 00783-011 OUTPUT ERROR (2mV/DIV) VS = ±18V 20 Figure 12. Typical Gain Error Normalized @ VOUT = 0 V and Output Voltage Operating Range vs. Supply Voltage (Curves Offset for Clarity) Rev. C | Page 6 of 16 AD629 20µV/DIV 40µV/DIV VS = ±15V RL = 2kΩ 2.5V/DIV –10 –5 0 VOUT (V) 5 00783-015 00783-012 ERROR (2ppm/DIV) ERROR (0.8ppm/DIV) VS = ±15V RL = 10kΩ 2V/DIV 10 –10 Figure 13. Gain Nonlinearity; VS = ±15 V, RL = 10 kΩ –8 –6 –4 –2 0 2 VOUT (V) 4 6 8 10 Figure 16. Gain Nonlinearity; VS = ±15 V, RL = 2kΩ 14.0 –40°C VS = ±12V RL = 10kΩ 13.0 –40°C ERROR (1ppm/DIV) OUTPUT VOLTAGE (V) 12.0 11.0 VS= ±15V –10 –8 –6 –4 –2 0 2 VOUT (V) 4 6 8 9.0 –11.5 –12.0 –40°C 00783-013 –13.0 –13.5 10 +25°C +85°C 0 2 4 6 8 10 12 14 OUTPUT CURRENT (mA) 16 11.5 VS = ±5V RL = 1kΩ –40°C –40°C OUTPUT VOLTAGE (V) ERROR (6.67ppm/DIV) 9.5 8.5 VS= ±12V +25°C 7.5 +85°C 6.5 –9.0 –9.5 –40°C –1.8 –1.2 –0.6 0 0.6 VOUT (V) 1.2 1.8 2.4 Figure 15. Gain Nonlinearity; VS = ±5 V, RL = 1 kΩ +25°C –10.5 –11.0 3.0 00783-017 00783-014 0.6V/DIV –2.4 20 +85°C 10.5 –10.0 –3.0 18 Figure 17. Output Voltage Operating Range vs. Output Current; VS = ±15 V Figure 14. Gain Nonlinearity; VS = ±12 V, RL =10 kΩ 40µV/DIV +25°C 10.0 –12.5 2V/DIV +85°C 00783-016 20µV/DIV +85°C 0 2 4 6 8 10 12 14 OUTPUT CURRENT (mA) 16 18 20 Figure 18. Output Voltage Operating Range vs. Output Current; VS = ±12 V Rev. C | Page 7 of 16 AD629 4.5 +85°C –40°C 3.5 +85°C 1.5 0.5 VS= ±5V +25°C +85°C –2.0 –2.5 –40°C –3.0 –4.0 +85°C +25°C 0 2 4 6 8 10 12 14 OUTPUT CURRENT (mA) 16 18 25mV/DIV Figure 19. Output Voltage Operating Range vs. Output Current; VS = ±5 V 110 100 G = +1 RL = 2kΩ CL = 1000pF –VS 90 80 70 60 50 30 1.0 10 100 FREQUENCY (Hz) 1k 25mV/DIV 4µs/DIV 10k Figure 20. Power Supply Rejection Ratio vs. Frequency 00783-022 40 0.1 Figure 23. Small Signal Pulse Response 5.0 4.5 G = +1 RL = 2kΩ CL = 1000pF 4.0 3.5 3.0 2.5 2.0 1.5 1.0 00783-020 VOLTAGE NOISE SPECTRAL DENSITY (µV/ Hz) Figure 22. Small Signal Pulse Response +VS 00783-019 POWER SUPPLY REJECTION RATIO (dB) 120 4µs/DIV 20 00783-021 00783-018 +25°C –3.5 0.5 0.01 0.1 1.0 10 100 FREQUENCY (Hz) 1k 10k 5V/DIV 5µs/DIV 100k Figure 21. Voltage Noise Spectral Density vs. Frequency Figure 24. Large Signal Pulse Response Rev. C | Page 8 of 16 00783-023 OUTPUT VOLTAGE (V) G = +1 RL = 2kΩ CL = 1000pF –40°C 2.5 AD629 5V/DIV 5V/DIV 0V +10V VOUT VOUT –10V OUTPUT ERROR OUTPUT ERROR 1mV/DIV 10µs/DIV 00783-024 1mV = 0.01% 1mV/DIV Figure 25. Settling Time to 0.01%, for 0 V to 10 V Output Step; G = −1, RL = 2 kΩ 300 200 150 100 150 100 0 150 –900 –600 –300 0 300 OFFSET VOLTAGE (µV) 600 900 Figure 29. Typical Distribution of Offset Voltage; Package Option N-8 400 400 N = 2180 n ≈ 200 PCS. FROM 10 ASSEMBLY LOTS 350 N = 2180 n ≈ 200 PCS. FROM 10 ASSEMBLY LOTS 300 250 200 150 250 200 150 100 50 50 00783-026 100 –400 –200 0 200 –1 GAIN ERROR (ppm) 400 0 –600 600 00783-029 NUMBER OF UNITS 300 0 –600 00783-028 00783-025 –100 –50 0 50 100 COMMON-MODE REJECTION RATIO (ppm) Figure 26. Typical Distribution of Common-Mode Rejection; Package Option N-8 NUMBER OF UNITS 200 50 50 350 N = 2180 n ≈ 200 PCS. FROM 10 ASSEMBLY LOTS 250 NUMBER OF UNITS NUMBER OF UNITS N = 2180 n ≈ 200 PCS. FROM 10 ASSEMBLY LOTS 250 0 –150 10µs/DIV Figure 28. Settling Time to 0.01% for 0 V to −10 V Output Step; G = −1, RL = 2kΩ 350 300 1mV = 0.01% 00783-027 0V –400 –200 0 200 +1 GAIN ERROR (ppm) 400 600 Figure 30. Typical Distribution of +1 Gain Error; Package Option N-8 Figure 27. Typical Distribution of −1 Gain Error; Package Option N-8 Rev. C | Page 9 of 16 AD629 THEORY OF OPERATION To achieve high common-mode voltage range, an internal resistor divider (Pin 3 or Pin 5) attenuates the noninverting signal by a factor of 20. Other internal resistors (Pin 1, Pin 2, and the feedback resistor) restore the gain to provide a differential gain of unity. The complete transfer function equals To reduce output drift, the op amp uses super beta transistors in its input stage. The input offset current and its associated temperature coefficient contribute no appreciable output voltage offset or drift, which has the added benefit of reducing voltage noise because the corner where 1/f noise becomes dominant is below 5 Hz. To reduce the dependence of gain accuracy on the op amp, the open-loop voltage gain of the op amp exceeds 20 million, and the PSRR exceeds 140 dB. REF(–) 1 VOUT = V (+IN) − V (−IN) –IN 2 Laser wafer trimming provides resistor matching so that common-mode signals are rejected while differential input signals are amplified. +IN 3 –VS 4 21.1kΩ 380kΩ 380kΩ 380kΩ 20kΩ AD629 8 NC 7 +VS 6 OUTPUT 5 REF(+) NC = NO CONNECT Figure 31. Functional Block Diagram Rev. C | Page 10 of 16 00783-001 The AD629 is a unity gain, differential-to-single-ended amplifier (diff amp) that can reject extremely high commonmode signals (in excess of 270 V with 15 V supplies). It consists of an operational amplifier (op amp) and a resistor network. AD629 APPLICATIONS BASIC CONNECTIONS REF (–) 1 +VS REF (–) 1 –IN RSHUNT 2 +IN 3 –VS (SEE TEXT) AD629 380kΩ 380kΩ +3V TO +18V 8 380kΩ 7 NC +VS 6 20kΩ 4 5 0.1µF (SEE TEXT) VOUT = ISHUNT × RSHUNT REF (+) 0.1µF NC = NO CONNECT –VS –3V TO –18V 00783-030 ISHUNT 21.1kΩ –IN ISHUNT RSHUNT 2 +IN 3 AD629 380kΩ 380kΩ VX 380kΩ VY –VS +VS 8 7 NC +VS 0.1µF 6 20kΩ 4 5 REF (+) OUTPUT = VOUT – VREF NC = NO CONNECT VREF 00783-031 Figure 32 shows the basic connections for operating the AD629 with a dual supply. A supply voltage of between ±3 V and ±18 V is applied between Pin 7 and Pin 4. Both supplies should be decoupled close to the pins using 0.1 μF capacitors. Electrolytic capacitors of 10 μF, also located close to the supply pins, may be required if low frequency noise is present on the power supply. While multiple amplifiers can be decoupled by a single set of 10 μF capacitors, each in amp should have its own set of 0.1 μF capacitors so that the decoupling point can be located right at the IC’s power pins. 21.1kΩ Figure 33. Operation with a Single Supply Applying a reference voltage to REF(+) and REF(–) and operating on a single supply reduces the input common-mode range of the AD629. The new input common-mode range depends upon the voltage at the inverting and noninverting inputs of the internal operational amplifier, labeled VX and VY in Figure 33. These nodes can swing to within 1 V of either rail. Therefore, for a (single) supply voltage of 10 V, VX and VY can range between 1 V and 9 V. If VREF is set to 5 V, the permissible common-mode range is +85 V to –75 V. The common-mode voltage ranges can be calculated by Figure 32. Basic Connections VCM (±) = 20 VX/VY(±) − 19 VREF The differential input signal, which typically results from a load current flowing through a small shunt resistor, is applied to Pin 2 and Pin 3 with the polarity shown to obtain a positive gain. The common-mode range on the differential input signal can range from −270 V to +270 V, and the maximum differential range is ±13 V. When configured as shown in Figure 32, the device operates as a simple gain-of-1, differential-to-singleended amplifier; the output voltage being the shunt resistance times the shunt current. The output is measured with respect to Pin 1 and Pin 5. Pin 1 and Pin 5 (REF(–) and REF(+)) should be grounded for a gain of unity and should be connected to the same low impedance ground plane. Failure to do this results in degraded commonmode rejection. Pin 8 is a no connect pin and should be left open. SINGLE-SUPPLY OPERATION Figure 33 shows the connections for operating the AD629 with a single supply. Because the output can swing to within only about 2 V of either rail, it is necessary to apply an offset to the output. This can be conveniently done by connecting REF(+) and REF(–) to a low impedance reference voltage (some ADCs provide this voltage as an output), which is capable of sinking current. Therefore, for a single supply of 10 V, VREF may be set to 5 V for a bipolar input signal. This allows the output to swing ±3 V around the central 5 V reference voltage. Alternatively, for unipolar input signals, VREF can be set to about 2 V, allowing the output to swing from 2 V (for a 0 V input) to within 2 V of the positive rail. SYSTEM-LEVEL DECOUPLING AND GROUNDING The use of ground planes is recommended to minimize the impedance of ground returns (and therefore the size of dc errors). Figure 34 shows how to work with grounding in a mixed-signal environment, that is, with digital and analog signals present. To isolate low level analog signals from a noisy digital environment, many data acquisition components have separate analog and digital ground returns. All ground pins from mixed-signal components, such as ADCs, should return through a low impedance analog ground plane. Digital ground lines of mixed-signal converters should also be connected to the analog ground plane. Typically, analog and digital grounds should be separated; however, it is also a requirement to minimize the voltage difference between digital and analog grounds on a converter, to keep them as small as possible (typically <0.3 V). The increased noise, caused by the converter’s digital return currents flowing through the analog ground plane, is typically negligible. Maximum isolation between analog and digital is achieved by connecting the ground planes back at the supplies. Note that Figure 34 suggests a “star” ground system for the analog circuitry, with all ground lines being connected, in this case, to the ADC’s analog ground. However, when ground planes are used, it is sufficient to connect ground pins to the nearest point on the low impedance ground plane. Rev. C | Page 11 of 16 AD629 Table 5 shows some sample error voltages generated by a common-mode voltage of 200 V dc with shunt resistors from 20 Ω to 2000 Ω. Assuming that the shunt resistor is selected to use the full ±10 V output swing of the AD629, the error voltage becomes quite significant as RSHUNT increases. DIGITAL POWER SUPPLY GND +5V 0.1µF 0.1µF 7 –IN 2 AD629 OUTPUT 6 REF(–) REF(+) 1 14 VDD AGND DGND +VS –VS 3 6 4 VIN1 3 VIN2 AD7892-2 Table 5. Error Resulting from Large Values of RSHUNT (Uncompensated Circuit) VDD GND 12 MICROPROCESSOR RS (Ω) 20 1000 2000 00783-032 4 +IN 1 5 Figure 34. Optimal Grounding Practice for a Bipolar Supply Environment with Separate Analog and Digital Supplies POWER SUPPLY GND +5V 0.1µF 0.1µF –IN 2 +VS AD629 VDD –VS VIN1 OUTPUT 6 VIN2 REF(–) REF(+) 1 REF (–) AGND DGND VDD ADC 1 GND MICROPROCESSOR 00783-033 +IN 3 4 Error Indicated (mA) 0.5 0.498 0.5 To measure low current or current near zero in a high commonmode environment, an external resistor equal to the shunt resistor value can be added to the low impedance side of the shunt resistor, as shown in Figure 36. 0.1µF 7 Error VOUT (V) 0.01 0.498 1 5 ISHUNT RCOMP –IN RSHUNT +IN 2 21.1kΩ AD629 380kΩ 380kΩ 380kΩ 3 Figure 35. Optimal Ground Practice in a Single-Supply Environment –VS If there is only a single power supply available, it must be shared by both digital and analog circuitry. Figure 35 shows how to minimize interference between the digital and analog circuitry. In this example, the ADC’s reference is used to drive Pin REF(+) and Pin REF(–). This means that the reference must be capable of sourcing and sinking a current equal to VCM/200 kΩ. As in the previous case, separate analog and digital ground planes should be used (reasonably thick traces can be used as an alternative to a digital ground plane). These ground planes should connect at the power supply’s ground pin. Separate traces (or power planes) should run from the power supply to the supply pins of the digital and analog circuits. Ideally, each device should have its own power supply trace, but these can be shared by a number of devices, as long as a single trace is not used to route current to both digital and analog circuitry. 7 6 20kΩ 4 0.1µF –VS +VS 8 5 NC 0.1µF +VS VOUT REF (+) NC = NO CONNECT Figure 36. Compensating for Large Sense Resistors OUTPUT FILTERING A simple 2-pole, low-pass Butterworth filter can be implemented using the OP177 after the AD629 to limit noise at the output, as shown in Figure 37. Table 6 gives recommended component values for various corner frequencies, along with the peak-topeak output noise for each case. REF (–) 1 USING A LARGE SENSE RESISTOR –IN 2 +IN 3 AD629 380kΩ 380kΩ +VS 8 380kΩ 7 +VS C1 0.1µF +VS R1 6 4 0.1µF NC 0.1µF R2 OP177 0.1µF VOUT C2 20kΩ –VS Insertion of a large value shunt resistance across the input pins, Pin 2 and Pin 3, will imbalance the input resistor network, introducing a common-mode error. The magnitude of the error will depend on the common-mode voltage and the magnitude of RSHUNT. 21.1kΩ 5 REF (+) –VS 00783-035 0.1µF 0.1µF 00783-034 ANALOG POWER SUPPLY –5V +5V GND NC = NO CONNECT Figure 37. Filtering of Output Noise Using a 2-Pole Butterworth Filter Table 6. Recommended Values for 2-Pole Butterworth Filter Corner Frequency R1 R2 C1 C2 Output Noise (p-p) No Filter 50 kHz 5 kHz 500 Hz 50 Hz 2.94 kΩ ± 1% 2.94 kΩ ± 1% 2.94 kΩ ± 1% 2.7 kΩ ± 10% 1.58 kΩ ± 1% 1.58 kΩ ± 1% 1.58 kΩ ± 1% 1.5 kΩ ± 10% 2.2 nF ± 10% 22 nF ± 10% 220 nF ± 10% 2.2 μF ± 20% 1 nF ± 10% 10 nF ± 10% 0.1 μF ± 10% 1 μF ± 20% 3.2 mV 1 mV 0.32 mV 100 μV 32 μV Rev. C | Page 12 of 16 AD629 OUTPUT CURRENT AND BUFFERING ERROR BUDGET ANALYSIS EXAMPLE 1 The AD629 is designed to drive loads of 2 kΩ to within 2 V of the rails but can deliver higher output currents at lower output voltages (see Figure 17). If higher output current is required, the output of the AD629 should be buffered with a precision op amp, such as the OP113, as shown in Figure 38. This op amp can swing to within 1 V of either rail while driving a load as small as 600 Ω. In the dc application that follows, the 10 A output current from a device with a high common-mode voltage (such as a power supply or current-mode amplifier) is sensed across a 1 Ω shunt resistor (see Figure 40). The common-mode voltage is 200 V, and the resistor terminals are connected through a long pair of lead wires located in a high noise environment, for example, 50 Hz/60 Hz, 440 V ac power lines. The calculations in Table 7 assume an induced noise level of 1 V at 60 Hz on the leads, in addition to a full-scale dc differential voltage of 10 V. The error budget table quantifies the contribution of each error source. Note that the dominant error source in this example is due to the dc common-mode voltage. 1 –IN +IN 2 3 21.1kΩ AD629 380kΩ 380kΩ +VS 8 380kΩ NC 0.1µF 7 0.1µF 6 VOUT OP113 0.1µF 4 5 0.1µF REF (+) –VS NC = NO CONNECT OUTPUT CURRENT 00783-036 –VS 20kΩ Figure 38. Output Buffering Application –IN 2 +IN 3 VREF AD629 380kΩ 380kΩ 380kΩ 380kΩ 8 NC +VS 7 0.1µF +IN 60Hz POWER LINE –VS 380kΩ 6 20kΩ 4 5 VOUT REF (+) 0.1µF NC = NO CONNECT Figure 40. Error Budget Analysis Example 1: VIN = 10 V Full-Scale, VCM = 200 V DC, RSHUNT = 1 Ω, 1 V p-p, 60 Hz Power-Line Interference 7 NC +VS 0.1µF VOUT 6 20kΩ 4 AD629 +VS 8 380kΩ 2 21.1kΩ 5 REF (+) 00783-037 THERMOCOUPLE 21.1kΩ –IN 3 While low level signals can be connected directly to the –IN and +IN inputs of the AD629, differential input signals can also be connected, as shown in Figure 39, to give a precise gain of 19. However, large common-mode voltages are no longer permissible. Cold junction compensation can be implemented using a temperature sensor, such as the AD590. 1 1 1Ω SHUNT A GAIN OF 19 DIFFERENTIAL AMPLIFIER REF (–) REF (–) 10 AMPS 200V CMDC TO GROUND 00783-038 REF (–) NC = NO CONNECT Figure 39. A Gain of 19 Thermocouple Amplifier Table 7. AD629 vs. INA117 Error Budget Analysis Example 1 (VCM = 200 V dc) Error Source ACCURACY, TA = 25°C Initial Gain Error Offset Voltage DC CMR (Over Temperature) AD629 INA117 Error, ppm of FS AD629 INA117 (0.0005 × 10)/10 V × 106 (0.001 V/10 V) × 106 (224 × 10-6 × 200 V)/10 V × 106 (0.0005 × 10)/10 V × 106 (0.002 V/10 V) × 106 (500 × 10-6 × 200 V)/10 V × 106 Total Accuracy Error 500 100 4480 5080 500 200 10,000 10,700 TEMPERATURE DRIFT (85°C) Gain Offset Voltage 10 ppm/°C × 60°C (20 μV/°C × 60°C) × 106/10 V 10 ppm/°C × 60°C (40 μV/°C × 60°C) × 106/10 V Total Drift Error 600 120 720 600 240 840 RESOLUTION Noise, Typical, 0.01 Hz to 10 Hz, μV p-p CMR, 60 Hz Nonlinearity 15 μV/10 V × 106 (141 × 10-6 × 1 V)/10 V × 106 (10-5 × 10 V)/10 V × 106 25 μV/10 V × 106 (500 × 10-6 × 1 V)/10 V × 106 (10-5 × 10 V)/10 V × 106 Total Resolution Error Total Error 2 14 10 26 5826 3 50 10 63 11,603 Rev. C | Page 13 of 16 AD629 ERROR BUDGET ANALYSIS EXAMPLE 2 OUTPUT CURRENT REF (–) 10 AMPS ±100V AC CM TO GROUND 1 –IN 2 21.1kΩ AD629 380kΩ 380kΩ 8 NC +VS 7 0.1µF 1Ω SHUNT +IN 3 60Hz POWER LINE 380kΩ 6 20kΩ –VS 4 5 VOUT REF (+) 00783-039 This application is similar to the previous example except that the sensed load current is from an amplifier with an ac common-mode component of ±100 V (frequency = 500 Hz) present on the shunt (see Figure 41). All other conditions are the same as before. Note that the same kind of power-line interference can happen as detailed in Example 1. However, the ac common-mode component of 200 V p-p coming from the shunt is much larger than the interference of 1 V p-p; therefore, this interference component can be neglected. 0.1µF NC = NO CONNECT Figure 41. Error Budget Analysis Example 2: VIN = 10 V Full-Scale, VCM = ±100 V at 500 Hz, RSHUNT =1 Ω Table 8. AD629 vs. INA117 AC Error Budget Example 2 (VCM = ±100 V @ 500 Hz) Error Source ACCURACY, TA = 25°C Initial Gain Error Offset Voltage AD629 INA117 Error, ppm of FS AD629 INA117 (0.0005 × 10)/10 V × 106 (0.001 V/10 V) × 106 (0.0005 × 10)/10 V × 106 (0.002 V/10 V) × 106 Total Accuracy Error 500 100 600 500 200 700 TEMPERATURE DRIFT (85°C) Gain Offset Voltage 10 ppm/°C × 60°C (20 μV/°C × 60°C) × 106/10 V 10 ppm/°C × 60°C (40 μV/°C × 60°C) × 106/10 V Total Drift Error 600 120 720 600 240 840 RESOLUTION Noise, Typical, 0.01 Hz to 10 Hz, μV p-p CMR, 60 Hz Nonlinearity AC CMR @ 500 Hz 15 μV/10 V × 106 (141 × 10-6 × 1 V)/10 V × 106 (10-5 × 10 V)/10 V × 106 (141 × 10-6 × 200 V)/10 V × 106 25 μV/10 V × 106 (500 × 10-6 × 1 V)/10 V × 106 (10-5 × 10 V)/10 V × 106 (500 × 10-6 × 200 V)/10 V × 106 Total Resolution Error Total Error 2 14 10 2820 2846 4166 3 50 10 10,000 10,063 11,603 Rev. C | Page 14 of 16 AD629 OUTLINE DIMENSIONS 0.400 (10.16) 0.365 (9.27) 0.355 (9.02) 8 5 1 4 0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 0.100 (2.54) BSC 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.060 (1.52) MAX 0.210 (5.33) MAX 0.015 (0.38) MIN 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) SEATING PLANE 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.195 (4.95) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) GAUGE PLANE 0.430 (10.92) MAX 0.005 (0.13) MIN 0.014 (0.36) 0.010 (0.25) 0.008 (0.20) 0.070 (1.78) 0.060 (1.52) 0.045 (1.14) 070606-A COMPLIANT TO JEDEC STANDARDS MS-001 CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS. Figure 42. 8-Lead Plastic Dual In-Line Package [PDIP] (N-8) Dimensions shown in inches and (millimeters) 5.00 (0.1968) 4.80 (0.1890) 8 1 5 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 6.20 (0.2441) 5.80 (0.2284) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 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 43. 8-Lead Standard Small Outline Package [SOIC_N] (R-8) Dimensions shown in millimeters and (inches) Rev. C | Page 15 of 16 012407-A 4.00 (0.1574) 3.80 (0.1497) AD629 ORDERING GUIDE Model 1 AD629AN AD629ANZ AD629AR AD629AR-REEL AD629AR-REEL7 AD629ARZ AD629ARZ-RL AD629ARZ-R7 AD629BNZ AD629BR AD629BR-REEL AD629BR-REEL7 AD629BRZ AD629BRZ-RL AD629BRZ-R7 AD629AC-WP 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C Package Description 8-Lead PDIP 8-Lead PDIP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N, 13-Inch Tape and Reel, 2,500 pieces 8-Lead SOIC_N, 7-Inch Tape and Reel, 1,000 pieces 8-Lead PDIP 8-Lead SOIC_N 8-Lead SOIC_N, 13-Inch Tape and Reel, 2,500 pieces 8-Lead SOIC_N, 7-Inch Tape and Reel, 1,000 pieces 8-Lead SOIC_N 8-Lead SOIC_N, 13-Inch Tape and Reel, 2,500 pieces 8-Lead SOIC_N, 7-Inch Tape and Reel, 1,000 pieces Die Z = RoHS Compliant Part. ©1999-2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00783-0-4/11(C) Rev. C | Page 16 of 16 Package Option N-8 N-8 R-8 R-8 R-8 R-8 R-8 R-8 N-8 R-8 R-8 R-8 R-8 R-8 R-8