AD626

Low Cost, Single-Supply Differential Amplifier AD626 FEATURES Pin Selectable Gains of 10 and 100 True Single-Supply Operation Single-Supply Range of +2.4 V to +10 V Dual-Supply Range of 1.2 V to 6 V Wide Output Voltage Range of 30 mV to 4.7 V Optional Low-Pass Filtering Excellent DC Performance Low Input Offset Voltage: 500 V Max Large Common-Mode Range: 0 V to +54 V Low Power: 1.2 mW (VS = +5 V) Good CMR of 90 dB Typ AC Performance Fast Settling Time: 24 s (0.01%) Includes Input Protection Series Resistive Inputs (RIN = 200 k ) RFI Filters Included Allows 50 V Continuous Overload APPLICATIONS Current Sensing Interface for Pressure Transducers, Position Indicators, Strain Gages, and Other Low Level Signal Sources PRODUCT DESCRIPTION CONNECTION DIAGRAM 8-Lead Plastic Mini-DIP (N) and SOIC (R) Packages 200k –IN ANALOG GND –VS 1 1/6 2 G = 30 7 G = 100 200k 8 +IN 3 100k 6 +VS FILTER 4 G=2 5 OUT AD626 range of this amplifier is equal to 6 (+VS – 1 V) which provides a +24 V CMR while operating from a +5 V supply. Fur thermore, the AD626 features a CMR of 90 dB typ. The amplifier’s inputs are protected against continuous overload of up to 50 V, and RFI filters are included in the attenuator network. The output range is +0.03 V to +4.9 V using a +5 V supply. The amplifier provides a preset gain of 10, but gains between 10 and 100 can be easily configured with an external resistor. Furthermore, a gain of 100 is available by connecting the G = 100 pin to analog ground. The AD626 also offers low-pass filter capability by connecting a capacitor between the filter pin and analog ground. The AD626A and AD626B operate over the industrial temperature range of –40°C to +85°C. The AD626 is available in two 8-lead packages: a plastic mini-DIP and SOIC. 25 The AD626 is a low cost, true single-supply differential amplifier designed for amplifying and low-pass filtering small differential voltages from sources having a large common-mode voltage. The AD626 can operate from either a single supply of +2.4 V to +10 V, or dual supplies of ±1.2 V to ±6 V. The input common-mode 140 INPUT COMMON-MODE RANGE – V COMMON-MODE REJECTION – dB 120 20 100 80 60 40 20 0 0.1 G = 10, 100 VS = +5V G = 100 VS = 5V 15 VCM FOR SINGLE AND DUAL SUPPLIES 10 G = 10 VS = 5V 5 VCM FOR DUAL SUPPLIES ONLY 1 10 100 1k FREQUENCY – Hz 10k 100k 1M 0 1 2 3 SUPPLY VOLTAGE – 4 V 5 Figure 1. Common-Mode Rejection vs. Frequency Figure 2. Input Common-Mode Range vs. Supply REV. D 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. 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 companies. One Technology Way, P Box 9106, Norwood, MA 02062-9106, U.S.A. .O. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved. AD626–SPECIFICATIONS SINGLE SUPPLY Model Parameter GAIN Gain Accuracy Gain = 10 Gain = 100 Over Temperature, TA = TMIN to TMAX Gain Linearity Gain = 10 Gain = 100 OFFSET VOLTAGE Input Offset Voltage vs. Temperature vs. Temperature vs. Supply Voltage (PSR) +PSR –PSR COMMON-MODE REJECTION +CMR Gain = 10, 100 ±CMR Gain = 10, 100 –CMR Gain = 10, 100* COMMON-MODE VOLTAGE RANGE +CMV Gain = 10 –CMV Gain = 10 INPUT Input Resistance Differential Common-Mode Input Voltage Range (Common-Mode) OUTPUT Output Voltage Swing Positive Negative Short Circuit Current +ISC NOISE Voltage Noise RTI Gain = 10 Gain = 100 Gain = 10 Gain = 100 DYNAMIC RESPONSE –3 dB Bandwidth Slew Rate, TMIN to TMAX Settling Time POWER SUPPLY Operating Range Quiescent Current TRANSISTOR COUNT RL = 10 k Gain = 10 Gain = 100 Gain = 10 Gain = 100 (@+VS = +5 V and TA = 25 C, unless otherwise noted.) Condition Total Error @ VOUT ≥ 100 mV dc @ VOUT ≥ 100 mV dc G = 10 G = 100 @ VOUT ≥ 100 mV dc @ VOUT ≥ 100 mV dc Min AD626A Typ Max Min AD626B Typ Max Unit 0.4 0.1 1.0 1.0 50 150 0.016 0.02 2.5 2.9 6 74 64 80 55 73 0.2 0.5 0.6 0.6 30 120 0.016 0.02 2.5 2.9 6 % % ppm/°C ppm/°C % % mV mV µV/°C dB dB dB dB dB V V 0.014 0.014 1.9 0.014 0.014 1.9 TMIN to TMAX, G = 10 or 100 TMIN to TMAX, G = 10 or 100 74 64 RL = 10 k f = 100 Hz, VCM = +24 V f = 10 kHz, VCM = +6 V f = 100 Hz, VCM = –2 V CMR > 85 dB CMR > 85 dB 66 55 60 80 66 90 64 85 +24 –2 80 66 90 64 85 +24 –2 200 100 6 (VS – l) 200 100 6 (VS – l) k k V 4.7 4.7 0.03 0.03 4.90 4.90 4.7 4.7 0.03 0.03 4.90 4.90 V V V V mA 12 12 f = 0.1 Hz–10 Hz f = 0.1 Hz–10 Hz f = 1 kHz f = 1 kHz VOUT = +1 V dc Gain = 10 Gain = 100 to 0.01%, 1 V Step TA = TMIN to TMAX Gain = 10 Gain = 100 Number of Transistors 2 2 0.25 0.25 100 0.22 0.17 24 5 0.16 0.23 46 12 0.20 0.29 2 2 0.25 0.25 100 0.22 0.17 22 5 0.16 0.23 46 10 0.20 0.29 µV p-p µV p-p µV/ Hz µV/ Hz kHz V/µs V/µs µs V mA mA 0.17 0.1 0.17 0.1 2.4 2.4 *At temperatures above 25°C, –CMV degrades at the rate of 12 mV/°C; i.e., @ 25°C CMV = –2 V, @ 85°C CMV = –1.28 V. Specifications subject to change without notice. –2– REV. D AD626 DUAL SUPPLY Model Parameter GAIN Gain Accuracy Gain = 10 Gain = 100 Over Temperature, TA = TMIN to TMAX Gain Linearity Gain = 10 Gain = 100 OFFSET VOLTAGE Input Offset Voltage vs. Temperature vs. Temperature vs. Supply Voltage (PSR) +PSR –PSR COMMON-MODE REJECTION +CMR Gain = 10, 100 ±CMR Gain = 10, 100 COMMON-MODE VOLTAGE RANGE +CMV Gain = 10 –CMV Gain = 10 INPUT Input Resistance Differential Common-Mode Input Voltage Range (Common-Mode) OUTPUT Output Voltage Swing Positive Negative Short Circuit Current +ISC –ISC NOISE Voltage Noise RTI Gain = 10 Gain = 100 Gain = 10 Gain = 100 DYNAMIC RESPONSE –3 dB Bandwidth Slew Rate, TMIN to TMAX Settling Time POWER SUPPLY Operating Range Quiescent Current TRANSISTOR COUNT Specifications subject to change without notice. (@+VS = 5 V and TA = 25 C, unless otherwise noted.) Condition Total Error RL = 10 k G = 10 G = 100 0.045 0.01 50 TMIN to TMAX, G = 10 or 100 TMIN to TMAX, G = 10 or 100 74 64 RL = 10 k f = 100 Hz, VCM = +24 V f = 10 kHz, VCM = 6 V CMR > 85 dB CMR > 85 dB 66 55 1.0 80 66 90 60 26.5 32.5 74 64 80 55 Min AD626A Typ Max Min AD626B Typ Max Unit 0.2 0.25 0.5 1.0 50 100 0.055 0.015 500 1.0 0.1 0.15 0.3 0.6 30 80 0.055 0.015 250 0.5 % % ppm/°C ppm/°C % % µV mV µV/°C dB dB dB dB V V 0.045 0.01 50 0.5 80 66 90 60 26.5 32.5 200 110 6 (VS – l) RL = 10 k Gain = 10, 100 Gain = 10 Gain = 100 200 110 6 (VS – l) k k V 4.7 –1.65 –1.45 4.90 –2.1 –1.8 12 0.5 4.7 –1.65 –1.45 4.90 –2.1 –1.8 12 0.5 V V V mA mA f = 0.1 Hz–10 Hz f = 0.1 Hz–10 Hz f = 1 kHz f = 1 kHz VOUT = +1 V dc Gain = 10 Gain = 100 to 0.01%, 1 V Step TA = TMIN to TMAX Gain = 10 Gain = 100 Number of Transistors 2 2 0.25 0.25 100 0.22 0.17 24 5 1.5 1.5 46 6 2 2 2 2 0.25 0.25 100 0.22 0.17 22 5 1.5 1.5 46 6 2 2 µV p-p µV p-p µV/ Hz µV/ Hz kHz V/µs V/µs µs V mA mA 0.17 0.1 0.17 0.1 1.2 1.2 REV. D –3– AD626 ABSOLUTE MAXIMUM RATINGS1 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +36V Internal Power Dissipation2 Peak Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +60 V Maximum Reversed Supply Voltage Limit . . . . . . . . . . . . . –34V Output Short Circuit Duration . . . . . . . . . . . . . . . . . . Indefinite Storage Temperature Range (N, R) . . . . . . . . . –65°C to +125°C Operating Temperature Range AD626A/AD626B . . . . . . . . . . . . . . . . . . . . –40°C to +85°C Lead Temperature Range (Soldering 60 sec) . . . . . . . . . +300°C NOTES 1 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 8-Lead Plastic Package: JA = 100°C/W; JC = 50°C/W. 8-Lead SOIC Package: JA = 155°C/W; JC = 40°C/W. ORDERING GUIDE Model AD626AN AD626AR AD626BN AD626AR-REEL AD626AR-REEL7 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 Package Description Plastic DIP Small Outline IC Plastic DIP 13" Tape and Reel 7" Tape and Reel Package Option N-8 R-8 N-8 METALLIZATION PHOTOGRAPH Dimensions shown in inches and (mm). CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD626 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. –4– REV. D Typical Performance Characteristics–AD626 25 6 VS = 5V GAIN = 10, 100 INPUT COMMON-MODE RANGE – V 5 20 POSITIVE OUTPUT VOLTAGE – V 4 V 5 4 3 15 VCM FOR SINGLE AND DUAL SUPPLIES 10 2 1 5 VCM FOR DUAL SUPPLIES ONLY 0 –1 0 1 2 3 SUPPLY VOLTAGE – 10 100 1k LOAD RESISTANCE – 10k TPC 1. Input Common-Mode Range vs. Supply TPC 4. Positive Output Voltage Swing vs. Resistive Load 5 POSITIVE OUTPUT VOLTAGE SWING – V TA = 25 C 4 SINGLE AND DUAL SUPPLY 3 NEGATIVE OUTPUT VOLTAGE – V –6 –5 –4 –3 GAIN = 10 2 DUAL SUPPLY ONLY 1 –2 GAIN = 100 –1 0 1 100 0 0 1 2 3 SUPPLY VOLTAGE – V 4 5 1k 10k LOAD RESISTANCE – 100k TPC 2. Positive Output Voltage Swing vs. Supply Voltage TPC 5. Negative Output Voltage Swing vs. Resistive Load –5 NEGATIVE OUTPUT VOLTAGE SWING – V TA = 25 C –4 CHANGE IN OFFSET VOLTAGE – V 4 5 30 –3 20 DUAL SUPPLY ONLY –2 10 –1 0 0 1 2 3 SUPPLY VOLTAGE – V 0 0 1 2 3 4 5 WARM-UP TIME – Minutes TPC 3. Negative Output Voltage Swing vs. Supply Voltage TPC 6. Change in Input Offset Voltage vs. Warm-Up Time REV. D –5– AD626 1000 100 VS = 5V DUAL SUPPLY CLOSED-LOOP GAIN GAIN = 100 100 COMMON-MODE REJECTION – dB 95 90 85 VS = +5V SINGLE SUPPLY GAIN = 10 10 VS = 5V DUAL SUPPLY 80 VS = 75 70 65 20 5 0 10 100 1k 10k FREQUENCY – Hz 100k 1M 22 24 26 28 INPUT COMMON-MODE VOLTAGE – V 30 TPC 7. Closed-Loop Gain vs. Frequency TPC 10. Common-Mode Rejection vs. Input Common- Mode Voltage for Dual-Supply Operation 140 100 COMMON-MODE REJECTION – dB COMMON-MODE REJECTION – dB 120 G = 10, 100 90 100 G = 10, 100 VS = +5 80 60 40 G = 10 VS = 5 20 0 0.1 G = 100 VS = 5 80 70 60 1 10 100 1k FREQUENCY – Hz 10k 100k 1M 0 20 40 60 80 INPUT SOURCE RESISTANCE MISMATCH – TPC 8. Common-Mode Rejection vs. Frequency TPC 11. Common-Mode Rejection vs. Input Source Resistance Mismatch 100 G = 10, 100 COMMON-MODE REJECTION – dB 95 90 ADDITIONAL GAIN ERROR – % 0.7 CURVE APPLIES TO ALL SUPPLY VOLTAGES AND GAINS BETWEEN 10 AND 100 0.6 0.5 0.4 0.3 85 80 VS = +5 75 70 65 –5 TOTAL GAIN ERROR = GAIN ACCURACY (FROM SPEC TABLE) + ADDITIONAL GAIN ERROR 0.2 0.1 0.0 10 100 SOURCE RESISTANCE MISMATCH – 1k 0 5 10 15 20 INPUT COMMON-MODE VOLTAGE – V 25 TPC 9. Common-Mode Rejection vs. Input CommonMode Voltage for Single-Supply Operation TPC 12. Additional Gain Error vs. Source Resistance Mismatch –6– REV. D AD626 0.16 0.15 G = 10 0.14 0.13 0.12 1 2 3 SUPPLY VOLTAGE – V 4 5 5 SECONDS PER HORIZONTAL DIVISION TPC 13. Quiescent Supply Current vs. Supply Voltage for Single-Supply Operation TPC 16. 0.1 Hz to 10 Hz RTI Voltage Noise. VS = ±5 V, Gain = 100 2.0 100 QUIESCENT CURRENT – mA 1.5 CLOSED-LOOP GAIN FOR VS = 60 5V AND +5V 1.0 0.5 20 0 1 2 3 SUPPLY VOLTAGE – V 4 5 2 V PER VERTICAL DIVISION 80 40 0 1 10 100 1k 10k VALUE OF RESISTOR RG – 100k 1M TPC 14. Quiescent Supply Current vs. Supply Voltage for Dual-Supply Operation QUIESCENT CURRENT – mA TPC 17. Closed-Loop Gain vs. RG 10 140 ALL CURVES FOR GAINS OF 10 OR 100 120 POWER SUPPLY REJECTION – dB Hz VOLTAGE NSD – V/ 1.0 GAIN = 10, 100 100 SINGLE AND DUAL –PSRR 80 0.1 VS = 5V DUAL SUPPLY 60 SINGLE +PSRR 40 DUAL DUAL +PSRR +PSRR 0.01 1 10 100 1k FREQUENCY – Hz 10k 100k 20 0.1 1 10 100 1k FREQUENCY – Hz 10k 100k 1M TPC 15. Noise Voltage Spectral Density vs. Frequency TPC 18. Power Supply Rejection vs. Frequency REV. D –7– AD626 100 90 100 90 10 0% 10 0% TPC 19. Large Signal Pulse Response. VS = ±5 V, G = 10 TPC 22. Large Signal Pulse Response. VS = +5 V, G = 100 100 90 100 90 10 0% 10 0% TPC 20. Large Signal Pulse Response. VS = ±5 V, G = 100 TPC 23. Settling Time. VS = ±5 V, G = 10 500mV 100 90 100 90 10 0% 10 0% TPC 21. Large Signal Pulse Response. VS = +5 V, G = 10 TPC 24. Settling Time. VS = ±5 V, G = 100 –8– REV. D AD626 100 90 100 90 10 0% 10 0% TPC 25. Settling Time. VS = +5 V, G = 10 TPC 26. Settling Time. VS = +5 V, G = 100 ERROR OUT 10k 2k +VS INPUT 20V p–p 10k 1k 10k AD626 –VS Figure 4 shows the main elements of the AD626. The signal inputs at Pins 1 and 8 are first applied to dual resistive attenuators R1 through R4 whose purpose is to reduce the peak common-mode voltage at the input to the preamplifier—a feedback stage based on the very low drift op amp A1. This allows the differential input voltage to be accurately amplified in the presence of large common-mode voltages six times greater than that which can be tolerated by the actual input to A1. As a result, the input CMR extends to six times the quantity (VS – 1 V). The overall commonmode error is minimized by precise laser-trimming of R3 and R4, thus giving the AD626 a common-mode rejection ratio (CMRR) of at least 10,000:1 (80 dB). To minimize the effect of spurious RF signals at the inputs due to rectification at the input to A1, small filter capacitors C1 and C2 are included. The output of A1 is connected to the input of A2 via a 100 k (R12) resistor to facilitate the low-pass filtering of the signal of interest (see Low-Pass Filtering section). The 200 k input impedance of the AD626 requires that the source resistance driving this amplifier be low in value (