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 ⴞ1.2 V to ⴞ6 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 CONNECTION DIAGRAM 8-Lead Plastic Mini-DIP (N) and SOIC (R) Packages 200k⍀ –IN +IN ANALOG GND 2 –VS 3 G = 30 7 G = 100 6 +VS 5 OUT 100k⍀ FILTER 4 G=2 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. PRODUCT DESCRIPTION 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 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. 25 120 100 G = 10, 100 VS = +5V 80 G = 100 VS = ⴞ5V 60 40 G = 10 VS = ⴞ5V 20 1 10 100 1k FREQUENCY – Hz 10k 100k 1M Figure 1. Common-Mode Rejection vs. Frequency INPUT COMMON-MODE RANGE – V 140 COMMON-MODE REJECTION – dB 8 1/6 APPLICATIONS Current Sensing Interface for Pressure Transducers, Position Indicators, Strain Gages, and Other Low Level Signal Sources 0 0.1 200k⍀ 1 20 ⴞVCM FOR SINGLE AND DUAL SUPPLIES 15 10 ⴞVCM FOR DUAL SUPPLIES ONLY 5 0 1 2 3 SUPPLY VOLTAGE – ⴞV 4 5 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.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved. Powered by TCPDF (www.tcpdf.org) IMPORTANT LINKS for the AD626* Last content update 09/10/2013 07:55 pm Newer Alternatives: AD8276 or the AD8278 difference amps for their faster speed, smaller foot print, wider supply voltage range, and lower costs. PARAMETRIC SELECTION TABLES DESIGN COLLABORATION COMMUNITY Find Similar Products By Operating Parameters Collaborate Online with the ADI support team and other designers about select ADI products. DOCUMENTATION AN-282: Fundamentals of Sampled Data Systems AN-244: A User’s Guide to I.C. Instrumentation Amplifiers AN-245: Instrumentation Amplifiers Solve Unusual Design Problems AN-671: Reducing RFI Rectification Errors in In-Amp Circuits AN-589: Ways to Optimize the Performance of a Difference Amplifier A Designer’s Guide to Instrumentation Amplifiers Auto-Zero Amplifiers High-performance Adder Uses Instrumentation Amplifiers Input Filter Prevents Instrumentation-amp RF-Rectification Errors The AD8221 - Setting a New Industry Standard for Instrumentation Amplifiers Applying Instrumentation Amplifiers Effectively: The Importance of an Input Ground Return Leading Inside Advertorials: Applying Instrumentation Amplifiers Effectively—The Importance of an Input Ground Return DESIGN TOOLS, MODELS, DRIVERS & SOFTWARE AD626 SPICE Macro-Model AD626A SPICE Macro-Model AD626B SPICE Macro-Model Follow us on Twitter: www.twitter.com/ADI_News Like us on Facebook: www.facebook.com/AnalogDevicesInc DESIGN SUPPORT Submit your support request here: Linear and Data Converters Embedded Processing and DSP Telephone our Customer Interaction Centers toll free: Americas: Europe: China: India: Russia: 1-800-262-5643 00800-266-822-82 4006-100-006 1800-419-0108 8-800-555-45-90 Quality and Reliability Lead(Pb)-Free Data SAMPLE & BUY AD626 View Price & Packaging Request Evaluation Board Request Samples Check Inventory & Purchase EVALUATION KITS & SYMBOLS & FOOTPRINTS Find Local Distributors Symbols and Footprints * This page was dynamically generated by Analog Devices, Inc. and inserted into this data sheet. Note: Dynamic changes to the content on this page (labeled 'Important Links') does not constitute a change to the revision number of the product data sheet. This content may be frequently modified. AD626–SPECIFICATIONS SINGLE SUPPLY (@+VS = +5 V and TA = 25ⴗC, unless otherwise noted.) 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 Condition Min Total Error @ VOUT ≥ 100 mV dc @ VOUT ≥ 100 mV dc G = 10 G = 100 @ VOUT ≥ 100 mV dc @ VOUT ≥ 100 mV dc RL = 10 k⍀ f = 100 Hz, VCM = +24 V f = 10 kHz, VCM = +6 V f = 100 Hz, VCM = –2 V COMMON-MODE VOLTAGE RANGE +CMV Gain = 10 –CMV Gain = 10 CMR > 85 dB CMR > 85 dB Negative DYNAMIC RESPONSE –3 dB Bandwidth Slew Rate, TMIN to TMAX Settling Time POWER SUPPLY Operating Range Quiescent Current TRANSISTOR COUNT 1.0 1.0 50 150 0.2 0.5 0.6 0.6 30 120 % % ppm/°C ppm/°C 0.014 0.014 0.016 0.02 0.014 0.014 0.016 0.02 % % 1.9 2.5 2.9 6 1.9 2.5 2.9 6 mV mV µV/°C dB dB 66 55 60 90 64 85 80 55 73 90 64 85 dB dB dB +24 –2 +24 –2 V V 200 100 6 (VS – l) 200 100 6 (VS – l) k⍀ k⍀ V 4.90 4.90 V V V V 12 12 mA 2 2 0.25 0.25 2 2 0.25 0.25 µV p-p µV p-p µV/冑Hz µV/冑Hz 100 0.22 0.17 22 kHz V/µs V/µs µs 0.17 0.1 2.4 Number of Transistors Unit 80 66 f = 0.1 Hz–10 Hz f = 0.1 Hz–10 Hz f = 1 kHz f = 1 kHz TA = TMIN to TMAX Gain = 10 Gain = 100 Max 74 64 4.7 4.7 0.03 0.03 VOUT = +1 V dc Gain = 10 Gain = 100 to 0.01%, 1 V Step AD626B Typ 80 66 Short Circuit Current +ISC NOISE Voltage Noise RTI Gain = 10 Gain = 100 Gain = 10 Gain = 100 Min 74 64 INPUT Input Resistance Differential Common-Mode Input Voltage Range (Common-Mode) RL = 10 k⍀ Gain = 10 Gain = 100 Gain = 10 Gain = 100 Max 0.4 0.1 TMIN to TMAX, G = 10 or 100 TMIN to TMAX, G = 10 or 100 COMMON-MODE REJECTION +CMR Gain = 10, 100 ±CMR Gain = 10, 100 –CMR Gain = 10, 100* OUTPUT Output Voltage Swing Positive AD626A Typ 4.90 4.90 4.7 4.7 0.03 0.03 100 0.22 0.17 24 5 0.16 0.23 46 0.17 0.1 12 0.20 0.29 2.4 5 0.16 0.23 10 0.20 0.29 V mA mA 46 *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 (@+VS = ⴞ5 V and TA = 25ⴗC, unless otherwise noted.) Model Parameter GAIN Gain Accuracy Gain = 10 Gain = 100 Over Temperature, TA = TMIN to TMAX Condition Min Total Error RL = 10 k⍀ TMIN to TMAX, G = 10 or 100 TMIN to TMAX, G = 10 or 100 COMMON-MODE REJECTION +CMR Gain = 10, 100 ±CMR Gain = 10, 100 RL = 10 k⍀ f = 100 Hz, VCM = +24 V f = 10 kHz, VCM = 6 V COMMON-MODE VOLTAGE RANGE +CMV Gain = 10 –CMV Gain = 10 CMR > 85 dB CMR > 85 dB RL = 10 k⍀ Gain = 10, 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 0.1 0.15 0.3 0.6 30 80 % % ppm/°C ppm/°C 0.045 0.01 0.055 0.015 0.045 0.01 0.055 0.015 % % 50 500 1.0 50 250 0.5 0.5 µV mV µV/°C dB dB 66 55 90 60 80 55 90 60 dB dB 26.5 32.5 26.5 32.5 V V 200 110 6 (VS – l) 200 110 6 (VS – l) k⍀ k⍀ V 4.90 –2.1 –1.8 V V V 12 0.5 12 0.5 mA mA 2 2 0.25 0.25 2 2 0.25 0.25 µV p-p µV p-p µV/冑Hz µV/冑Hz 100 0.22 0.17 22 kHz V/µs V/µs µs ⫾1.2 4.90 –2.1 –1.8 –3– 4.7 –1.65 –1.45 100 0.22 0.17 24 ⫾5 1.5 1.5 46 Specifications subject to change without notice. REV. D 0.5 1.0 50 100 80 66 0.17 0.1 Number of Transistors Unit 74 64 f = 0.1 Hz–10 Hz f = 0.1 Hz–10 Hz f = 1 kHz f = 1 kHz TA = TMIN to TMAX Gain = 10 Gain = 100 Max 80 66 4.7 –1.65 –1.45 VOUT = +1 V dc Gain = 10 Gain = 100 to 0.01%, 1 V Step AD626B Typ 74 64 Short Circuit Current +ISC –ISC NOISE Voltage Noise RTI Gain = 10 Gain = 100 Gain = 10 Gain = 100 Min 1.0 INPUT Input Resistance Differential Common-Mode Input Voltage Range (Common-Mode) OUTPUT Output Voltage Swing Positive Negative Max 0.2 0.25 G = 10 G = 100 Gain Linearity Gain = 10 Gain = 100 OFFSET VOLTAGE Input Offset Voltage vs. Temperature vs. Temperature vs. Supply Voltage (PSR) +PSR –PSR AD626A Typ 0.17 0.1 ⫾6 2 2 ⫾1.2 ⫾5 1.5 1.5 46 ⫾6 2 2 V mA mA AD626 ABSOLUTE MAXIMUM RATINGS1 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. 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 ORDERING GUIDE Model Temperature Range Package Description Package Option AD626AN AD626AR AD626BN AD626AR-REEL AD626AR-REEL7 –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 Plastic DIP Small Outline IC Plastic DIP 13" Tape and Reel 7" Tape and Reel 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 6 VS = ⴞ5V GAIN = 10, 100 5 POSITIVE OUTPUT VOLTAGE – V INPUT COMMON-MODE RANGE – V 25 20 ⴞVCM FOR SINGLE AND DUAL SUPPLIES 15 10 ⴞVCM FOR DUAL SUPPLIES ONLY 5 0 4 3 2 1 0 –1 1 2 3 4 5 10 100 1k LOAD RESISTANCE – ⍀ SUPPLY VOLTAGE – ⴞV TPC 1. Input Common-Mode Range vs. Supply TPC 4. Positive Output Voltage Swing vs. Resistive Load –6 TA = 25ⴗC NEGATIVE OUTPUT VOLTAGE – V POSITIVE OUTPUT VOLTAGE SWING – V 5 4 SINGLE AND DUAL SUPPLY 3 2 DUAL SUPPLY ONLY 1 –5 –4 –3 GAIN = 10 –2 GAIN = 100 –1 0 0 0 1 2 3 SUPPLY VOLTAGE – V 4 1 100 5 TPC 2. Positive Output Voltage Swing vs. Supply Voltage 1k 10k LOAD RESISTANCE – ⍀ 100k TPC 5. Negative Output Voltage Swing vs. Resistive Load –5 30 TA = 25ⴗC CHANGE IN OFFSET VOLTAGE – V NEGATIVE OUTPUT VOLTAGE SWING – V 10k –4 –3 DUAL SUPPLY ONLY –2 –1 0 0 1 2 3 SUPPLY VOLTAGE – V 4 20 10 0 5 0 1 2 3 4 5 WARM-UP TIME – Minutes TPC 3. Negative Output Voltage Swing vs. Supply Voltage REV. D TPC 6. Change in Input Offset Voltage vs. Warm-Up Time –5– AD626 100 COMMON-MODE REJECTION – dB 1000 VS = ⴞ5V DUAL SUPPLY CLOSED-LOOP GAIN GAIN = 100 100 VS = +5V SINGLE SUPPLY GAIN = 10 10 VS = ⴞ5V DUAL SUPPLY 0 10 100 90 85 80 VS = ⴞ5 75 70 1k 10k FREQUENCY – Hz 100k 65 20 1M TPC 7. Closed-Loop Gain vs. Frequency 22 24 26 28 INPUT COMMON-MODE VOLTAGE – V 30 TPC 10. Common-Mode Rejection vs. Input Common- Mode Voltage for Dual-Supply Operation 100 140 COMMON-MODE REJECTION – dB 120 COMMON-MODE REJECTION – dB 95 100 G = 10, 100 VS = +5 80 G = 100 VS = ⴞ5 60 40 G = 10 VS = ⴞ5 G = 10, 100 90 80 70 20 0 0.1 60 1 10 100 1k FREQUENCY – Hz 10k 100k 1M 0 TPC 8. Common-Mode Rejection vs. Frequency 60 80 0.7 G = 10, 100 95 CURVE APPLIES TO ALL SUPPLY VOLTAGES AND GAINS BETWEEN 10 AND 100 0.6 ADDITIONAL GAIN ERROR – % COMMON-MODE REJECTION – dB 40 TPC 11. Common-Mode Rejection vs. Input Source Resistance Mismatch 100 90 85 80 VS = +5 75 70 65 –5 20 INPUT SOURCE RESISTANCE MISMATCH – ⍀ 0.5 TOTAL GAIN ERROR = GAIN ACCURACY (FROM SPEC TABLE) + ADDITIONAL GAIN ERROR 0.4 0.3 0.2 0.1 0 5 10 15 20 INPUT COMMON-MODE VOLTAGE – V 0.0 25 10 TPC 9. Common-Mode Rejection vs. Input CommonMode Voltage for Single-Supply Operation 100 SOURCE RESISTANCE MISMATCH – ⍀ 1k TPC 12. Additional Gain Error vs. Source Resistance Mismatch –6– REV. D AD626 2V PER VERTICAL DIVISION QUIESCENT CURRENT – mA 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 = 100 100 80 1.5 CLOSED-LOOP GAIN QUIESCENT CURRENT – mA 2.0 1.0 FOR VS = ⴞ5V AND +5V 60 40 0.5 20 0 ⴞ1 ⴞ2 ⴞ3 SUPPLY VOLTAGE – V ⴞ4 0 ⴞ5 1 TPC 14. Quiescent Supply Current vs. Supply Voltage for Dual-Supply Operation POWER SUPPLY REJECTION – dB Hz VOLTAGE NSD – V/ 100k 1M 140 1.0 GAIN = 10, 100 0.1 VS = ⴞ5V DUAL SUPPLY 1 10 100 1k FREQUENCY – Hz 10k ALL CURVES FOR GAINS OF 10 OR 100 120 100 SINGLE AND DUAL –PSRR 80 60 SINGLE +PSRR 40 20 0.1 100k TPC 15. Noise Voltage Spectral Density vs. Frequency REV. D 100 1k 10k VALUE OF RESISTOR RG – ⍀ TPC 17. Closed-Loop Gain vs. RG 10 0.01 10 DUAL DUAL +PSRR +PSRR 1 10 100 1k FREQUENCY – Hz 10k 100k 1M TPC 18. Power Supply Rejection vs. Frequency –7– AD626 100 100 90 90 10 10 0% 0% TPC 19. Large Signal Pulse Response. VS = ±5 V, G = 10 TPC 22. Large Signal Pulse Response. VS = +5 V, G = 100 100 100 90 90 10 10 0% 0% TPC 20. Large Signal Pulse Response. VS = ±5 V, G = 100 TPC 23. Settling Time. VS = ±5 V, G = 10 500mV 100 100 90 90 10 10 0% 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 100 100 90 90 10 10 0% 0% TPC 25. Settling Time. VS = +5 V, G = 10 TPC 26. Settling Time. VS = +5 V, G = 100 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). ERROR OUT 10k⍀ 10k⍀ 2k⍀ +VS INPUT 20V p–p 10k⍀ AD626 1k⍀ –VS Figure 3. Settling Time Test Circuit 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. THEORY OF OPERATION The AD626 is a differential amplifier consisting of a precision balanced attenuator, a very low drift preamplifier (A1), and an output buffer amplifier (A2). It has been designed so that small differential signals can be accurately amplified and filtered in the presence of large common-mode voltages (VCM), without the use of any other active components. 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 (<1 k⍀)—this is +VS R1 200k⍀ FILTER C1 5pF AD626 R12 100k⍀ +IN A1 A2 –IN R2 200k⍀ R3 41k⍀ R11 10k⍀ R6 500⍀ R4 41k⍀ R5 4.2k⍀ R7 500⍀ R17 95k⍀ R15 10k⍀ R9 10k⍀ R8 10k⍀ R10 10k⍀ R14 555⍀ GAIN = 100 GND Figure 4. Simplified Schematic REV. D OUT C2 5pF –9– R13 10k⍀ –VS AD626 necessary to minimize gain error. Also, any mismatch between the total source resistance at each input will affect gain accuracy and common-mode rejection (CMR). For example: when operating at a gain of 10, an 80 ⍀ mismatch in the source resistance between the inputs will degrade CMR to 68 dB. +INPUT –INPUT 200k⍀ –IN 200k⍀ +IN 2 –VS 3 ANALOG GND G = 100 7 G = 30 –VS +VS +VS 6 100k⍀ 0.1F The output of amplifier A2 relies on a 10 k⍀ resistor to –VS for “pull-down.” For single-supply operation, (–VS = “GND”), A2 can drive a 10 k⍀ ground referenced load to at least +4.7 V. The minimum, nominally “zero,” output voltage will be 30 mV. For dual-supply operation (±5 V), the positive output voltage swing will be the same as for a single supply. The negative swing will be to –2.5 V, at G = 100, limited by the ratio: 4 0.1F OUT FILTER G=2 OUTPUT 5 AD626 Figure 6. AD626 Configured for a Gain of 100 +INPUT R15 + R14 R13 + R14 + R15 –INPUT 1 200k⍀ –IN 200k⍀ +IN 8 1/6 The negative range can be extended to –3.3 V (G = 100) and –4 V (G = 10) by adding an external 10 k⍀ pull-down from the output to –VS. This will add 0.5 mA to the AD626’s quiescent current, bringing the total to 2 mA. 2 –VS 3 ANALOG GND CF FILTER (OPTIONAL) RH G = 100 7 +VS +VS 6 100k⍀ 4 RG G = 30 –VS 0.1F The AD626’s 100 kHz bandwidth at G = 10 and 100 (a 10 MHz gain bandwidth) is much higher than can be obtained with low power op amps in discrete differential amplifier circuits. Fur thermore, the AD626 is stable driving capacitive loads up to 50 pF (G10) or 200 pF (G100). Capacitive load drive can be increased to 200 pF (G10) by connecting a 100 ⍀ resistor in series with the AD626’s output and the load. 0.1F FILTER OUT G=2 OUTPUT 5 AD626 CORNER FREQUENCY OF FILTER = 1 2CF (100k⍀) RESISTOR VALUES FOR GAIN ADJUSTMENT GAIN RANGE ADJUSTING THE GAIN OF THE AD626 11 – 20 20 – 40 40 – 80 80 – 100 The AD626 is easily configured for gains of 10 or 100. Figure 5 shows that for a gain of 10, Pin 7 is simply left unconnected; similarly, for a gain of 100, Pin 7 is grounded, as shown in Figure 6. Gains between 10 and 100 are easily set by connecting a variable resistance between Pin 7 and Analog GND, as shown in Figure 7. Because the on-chip resistors have an absolute tolerance of ±20% (although they are ratio matched to within 0.1%), at least a 20% adjustment range must be provided. The values shown in the table in Figure 7 provide a good trade-off between gain set range and resolution, for gains from 11 to 90. 8 1/6 The output buffer, A2, operates at a gain of 2 or 20, thus setting the overall, precalibrated gain of the AD626 (with no external components) at 10 or 100. The gain is set by the feedback network around amplifier A2. –VS × 1 RG(⍀) RH(⍀) 100k 10k 1k 100 4.99k 802 80 2 Figure 7. Recommended Circuit for Gain Adjustment SINGLE-POLE LOW-PASS FILTERING A low-pass filter can be easily implemented by using the features provided by the AD626. By simply connecting a capacitor between Pin 4 and ground, a single-pole low-pass filter is created, as shown in Figure 8. +INPUT +INPUT –INPUT 1 200k⍀ –IN 200k⍀ +IN 8 –INPUT 1 200k⍀ –IN 200k⍀ +IN 8 1/6 2 –VS 3 ANALOG GND G = 10 7 G = 30 –VS +VS 6 100k⍀ 0.1F 4 FILTER NOT CONNECTED 1/6 2 OUT G = 100 7 G = 30 +VS 3 0.1F G=2 ANALOG GND –VS +VS 6 100k⍀ 5 OUTPUT 4 AD626 CF Figure 5. AD626 Configured for a Gain of 10 FILTER +10V 0.1F OUT G=2 5 OUTPUT AD626 CORNER FREQUENCY OF FILTER = 1 2CF (100k⍀) Figure 8. A One-Pole Low-Pass Filter Circuit Which Operates from a Single +10 V Supply –10– REV. D AD626 CURRENT SENSOR INTERFACE BRIDGE APPLICATION A typical current sensing application, making use of the large common-mode range of the AD626, is shown in Figure 9. The current being measured is sensed across resistor RS. The value of RS should be less than 1 k⍀ and should be selected so that the average differential voltage across this resistor is typically 100 mV. Figure 10 shows the AD626 in a typical bridge application. Here, the AD626 is set to operate at a gain of 100, using dual-supply voltages and offering the option of low-pass filtering. +VS To produce a full-scale output of +4 V, a gain of 40 is used adjustable by ±20% to absorb the tolerance in the sense resistor. Note that there is sufficient headroom to allow at least a 10% overrange (to +4.4 V). 1 200k⍀ –IN CURRENT OUT –5V RS 1 200k⍀ –IN 200k⍀ +IN 2 ANALOG GND –VS 3 CF OPTIONAL LOW-PASS FILTER 7 G = 30 –VS +VS 6 100k⍀ 0.1F 4 FILTER CF OPTIONAL LOW-PASS FILTER RG 5 OUTPUT AD626 Figure 9. Current Sensor Interface REV. D 7 –VS +VS 6 4 FILTER +5V 0.1F OUT G=2 5 AD626 Figure 10. A Typical Bridge Application +VS 0.1F OUT G=2 G = 100 G = 30 100k⍀ 8 RH G = 100 3 0.1F 1/6 ANALOG GND 8 1/6 2 CURRENT IN CURRENT SENSOR 200k⍀ +IN –11– OUTPUT AD626 OUTLINE DIMENSIONS 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) C00781–0–1/03(D) Dimensions shown in millimeters and (inches) 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 8 5 1 4 6.20 (0.2440) 5.80 (0.2284) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY SEATING 0.10 PLANE 0.50 (0.0196) ⴛ45ⴗ 0.25 (0.0099) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.33 (0.0130) 8ⴗ 0.25 (0.0098) 0ⴗ 1.27 (0.0500) 0.41 (0.0160) 0.19 (0.0075) COMPLIANT TO JEDEC STANDARDS MS-012AA 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 8-Lead Plastic Dual-In Line Package [PDIP] (N-8) Dimensions shown in inches and (millimeters) 0.375 (9.53) 0.365 (9.27) 0.355 (9.02) 8 5 1 4 0.295 (7.49) 0.285 (7.24) 0.275 (6.98) 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.100 (2.54) BSC 0.180 (4.57) MAX 0.150 (3.81) 0.130 (3.30) 0.110 (2.79) 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.015 (0.38) MIN SEATING PLANE 0.060 (1.52) 0.050 (1.27) 0.045 (1.14) 0.150 (3.81) 0.135 (3.43) 0.120 (3.05) 0.015 (0.38) 0.010 (0.25) 0.008 (0.20) Revision History Location Page 1/03—Data Sheet changed from REV. C to REV. D. Renumbered Figures and TPCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Universal Edits to Figure 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Edits to SPECIFICATIONS, Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Edit to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Update to standard CAUTION/ESD Warning note and diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Edits to TPC 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 –12– REV. D PRINTED IN U.S.A. COMPLIANT TO JEDEC STANDARDS MO-095AA 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