Low Cost, Single-Supply Differential Amplifi er AD626

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1 FEATURES Pin Selectable Gains of and True Single-Supply Operation Single-Supply Range of +. V to + V Dual-Supply Range of. V to 6 V Wide Output Voltage Range of mv to.7 V Optional Low-Pass Filtering Excellent DC Performance Low Input Offset Voltage: V Max Large Common-Mode Range: V to + V Low Power:. mw (V S = + V) Good CMR of 9 db Typ AC Performance Fast Settling Time: s (.%) Includes Input Protection Series Resistive Inputs (R IN = k ) RFI Filters Included Allows V Continuous Overload APPLICATIONS Current Sensing Interface for Pressure Transducers, Position Indicators, Strain Gages, and Other Low Level Signal Sources PROD UCT DE SCRIP TION The AD66 is a low cost, true sin gle-sup ply dif fer en tial am pli fi er de signed for am pli fy ing and low-pass filtering small dif fer en tial voltages from sources having a large common-mode voltage. The AD66 can operate from either a single supply of +. V to + V, or dual supplies of ±. V to ±6 V. The input common-mode Low Cost, Single-Supply Differential Amplifi er AD66 CONNECTION DIAGRAM -Lead Plastic Mini-DIP (N) and SOIC (R) Packages ANALOG GND k AD66 /6 G = G = range of this amplifier is equal to 6 ( V) which pro vides a + V CMR while operating from a + V sup ply. Fur ther more, the AD66 features a CMR of 9 db typ. The amplifier s inputs are protected against continuous overload of up to V, and RFI filters are included in the attenuator network. The output range is +. V to +.9 V using a + V sup ply. The amplifier provides a preset gain of, but gains be tween and can be easily con fig ured with an external re sis tor. Fur ther - more, a gain of is available by connecting the G = pin to analog ground. The AD66 also offers low-pass filter capability by connecting a ca pac i tor between the filter pin and analog ground. The AD66A and AD66B operate over the industrial tem per a ture range of C to + C. The AD66 is available in two -lead packages: a plastic mini-dip and SOIC. 7 6 G = COMMON-MODE REJECTION db 6 G =, V S = +V G = V S = V G = V S = V INPUT COMMON-MODE RANGE V V CM FOR SINGLE AND DUAL SUPPLIES V CM FOR DUAL SUPPLIES ONLY. k FREQUENCY Hz k k M SUPPLY VOLTAGE V Figure. Common-Mode Rejection vs. Frequency Figure. Input Common-Mode Range vs. Supply Information furnished by Analog Devices is be lieved 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 96, Norwood, MA 6-96, U.S.A. Tel: 7/9-7 Fax: 7/6-7 Analog Devices, Inc. All rights reserved.

2 AD66* PRODUCT PAGE QUICK LINKS Last Content Update: //7 COMPARABLE PARTS View a parametric search of comparable parts. DOCUMENTATION Application Notes AN-: A User's Guide to I.C. Instrumentation Amplifiers AN-: Instrumentation Amplifiers Solve Unusual Design Problems AN-: Fundamentals of Sampled Data Systems AN-9: Ways to Optimize the Performance of a Difference Amplifier AN-67: Reducing RFI Rectification Errors in In-Amp Circuits Data Sheet AD66: Low Cost, Single Supply Differential Amplifier Data Sheet Technical Books A Designer's Guide to Instrumentation Amplifiers, rd Edition, 6 TOOLS AND SIMULATIONS AD66 SPICE Macro-Model REFERENCE MATERIALS Technical Articles Auto-Zero Amplifiers High-performance Adder Uses Instrumentation Amplifiers Input Filter Prevents Instrumentation-amp RF- Rectification Errors The AD - Setting a New Industry Standard for Instrumentation Amplifiers DESIGN RESOURCES AD66 Material Declaration PCN-PDN Information Quality And Reliability Symbols and Footprints DISCUSSIONS View all AD66 EngineerZone Discussions. SAMPLE AND BUY Visit the product page to see pricing options. TECHNICAL SUPPORT Submit a technical question or find your regional support number. DOCUMENT FEEDBACK Submit feedback for this data sheet. This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.

3 AD66 SPECIFICATIONS SINGLE SUPPLY = + V and T A = C, un less oth er wise noted.) Model AD66A AD66B Parameter Condition Min Typ Max Min Typ Max Unit GAIN Gain Accuracy Total Error Gain V mv dc....6 % Gain V mv dc....6 % Over Temperature, T A = T MIN to T MAX G = ppm/ C G = ppm/ C Gain Linearity Gain V mv dc % Gain V mv dc.... % OFFSET VOLTAGE Input Offset Voltage mv vs. Temperature T MIN to T MAX, G = or.9.9 mv vs. Temperature T MIN to T MAX, G = or 6 6 µv/ C vs. Supply Voltage (PSR) +PSR 7 7 db PSR db COMMON-MODE REJECTION R L = k +CMR Gain =, f = Hz, V CM = + V db ±CMR Gain =, f = khz, V CM = +6 V 6 6 db CMR Gain =, * f = Hz, V CM = V 6 7 db COMMON-MODE VOLTAGE RANGE +CMV Gain = CMR > db + + V CMV Gain = CMR > db V INPUT Input Resistance Differential k Common-Mode k Input Voltage Range (Common-Mode) 6 (V S l) 6 (V S l) V PUT Output Voltage Swing R L = k Positive Gain = V Gain = V Negative Gain =.. V Gain =.. V Short Circuit Current +I SC ma NOISE Voltage Noise RTI Gain = f =. Hz Hz µv p-p Gain = f =. Hz Hz µv p-p Gain = f = khz.. µv/ Hz Gain = f = khz.. µv/ Hz DYNAMIC RESPONSE db Bandwidth V = + V dc khz Slew Rate, T MIN to T MAX Gain = V/µs Gain = V/µs Settling Time to.%, V Step µs POWER SUPPLY Operating Range T A = T MIN to T MAX.. V Quiescent Current Gain = ma Gain = ma TRANSISTOR COUNT Number of Transistors 6 6 *At temperatures above C, CMV degrades at the rate of mv/ C; C CMV = C CMV =. V. Specifications subject to change without notice.

4 DUAL SUPPLY = V and T A = C, un less oth er wise noted.) AD66 Model AD66A AD66B Parameter Condition Min Typ Max Min Typ Max Unit GAIN Gain Accuracy Total Error Gain = R L = k.... % Gain =....6 % Over Temperature, T A = T MIN to T MAX G = ppm/ C G = ppm/ C Gain Linearity Gain =.... % Gain =.... % OFFSET VOLTAGE Input Offset Voltage µv vs. Temperature T MIN to T MAX, G = or.. mv vs. Temperature T MIN to T MAX, G = or.. µv/ C vs. Supply Voltage (PSR) +PSR 7 7 db PSR db COMMON-MODE REJECTION R L = k +CMR Gain =, f = Hz, V CM = + V db ±CMR Gain =, f = khz, V CM = 6 V 6 6 db COMMON-MODE VOLTAGE RANGE +CMV Gain = CMR > db V CMV Gain = CMR > db.. V INPUT Input Resistance Differential k Common-Mode k Input Voltage Range (Common-Mode) 6 (V S l) 6 (V S l) V PUT Output Voltage Swing R L = k Positive Gain =, V Negative Gain = V Gain =.... V Short Circuit Current +I SC ma I SC.. ma NOISE Voltage Noise RTI Gain = f =. Hz Hz µv p-p Gain = f =. Hz Hz µv p-p Gain = f = khz.. µv/ Hz Gain = f = khz.. µv/ Hz DYNAMIC RESPONSE db Bandwidth V = + V dc khz Slew Rate, T MIN to T MAX Gain = V/µs Gain = V/µs Settling Time to.%, V Step µs POWER SUPPLY Operating Range T A = T MIN to T MAX V Quiescent Current Gain =.. ma Gain =.. ma TRANSISTOR COUNT Number of Transistors 6 6 Specifications subject to change without notice.

5 AD66 ABSOLUTE MAXIMUM RATINGS Supply Voltage V Internal Power Dissipation Peak Input Voltage V Maximum Reversed Supply Voltage Limit V Output Short Circuit Duration Indefinite Storage Temperature Range (N, R) C to + C Operating Temperature Range AD66A/AD66B C to + C Lead Temperature Range (Soldering 6 sec) C NOTES Stresses above those listed under Absolute Max i mum Ratings may cause per ma nent 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 ab so lute maximum rating con di tions for extended periods may affect device re li abil i ty. -Lead Plastic Package: JA = C/W; JC = C/W. -Lead SOIC Package: JA = C/W; JC = C/W. ORDERING GUIDE Temperature Package Package Model Range Description Option AD66AN C to + C Plastic DIP N- AD66AR C to + C Small Outline IC R- AD66BN C to + C Plastic DIP N- AD66AR-REEL C to + C " Tape and Reel AD66AR-REEL7 C to + C 7" Tape and Reel METALLIZATION PHOTOGRAPH Dimensions shown in inches and (mm). CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as V readily ac cu mu late on the human body and test equipment and can discharge without detection. Although the AD66 features proprietary ESD pro tec tion circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD pre cau tions are rec om mend ed to avoid per for mance deg ra da tion or loss of functionality.

6 Typical Performance Characteristics AD66 6 INPUT COMMON-MODE RANGE V V CM FOR SINGLE AND DUAL SUPPLIES V CM FOR DUAL SUPPLIES ONLY POSITIVE PUT VOLTAGE V V S = V GAIN =, SUPPLY VOLTAGE V k k LOAD RESISTANCE TPC. Input Common-Mode Range vs. Supply TPC. Positive Output Voltage Swing vs. Resistive Load 6 POSITIVE PUT VOLTAGE SWING V T A = C SINGLE AND DUAL SUPPLY DUAL SUPPLY ONLY NEGATIVE PUT VOLTAGE V GAIN = GAIN = SUPPLY VOLTAGE V k k k LOAD RESISTANCE TPC. Positive Output Voltage Swing vs. Supply Voltage TPC. Negative Output Voltage Swing vs. Resistive Load NEGATIVE PUT VOLTAGE SWING V T A = C DUAL SUPPLY ONLY CHANGE IN OFFSET VOLTAGE V SUPPLY VOLTAGE V WARM-UP TIME Minutes TPC. Negative Output Voltage Swing vs. Supply Voltage TPC 6. Change in Input Offset Voltage vs. Warm-Up Time

7 AD66 CLOSED-LOOP GAIN GAIN = GAIN = V S = +V SINGLE SUPPLY V S = V DUAL SUPPLY V S = V DUAL SUPPLY COMMON-MODE REJECTION db V S = k k k M FREQUENCY Hz 6 6 INPUT COMMON-MODE VOLTAGE V TPC 7. Closed-Loop Gain vs. Frequency TPC. Common-Mode Rejection vs. Input Common- Mode Voltage for Dual-Supply Operation COMMON-MODE REJECTION db 6 G =, V S = + G = V S = G = V S = COMMON-MODE REJECTION db 9 7 G =,. k FREQUENCY Hz k k M 6 6 INPUT SOURCE RESISTANCE MISMATCH TPC. Common-Mode Rejection vs. Frequency TPC. Common-Mode Rejection vs. Input Source Resistance Mismatch COMMON-MODE REJECTION db G =, V S = + ADDITIONAL GAIN ERROR % CURVE APPLIES TO ALL SUPPLY VOLTAGES AND GAINS BETWEEN AND TOTAL GAIN ERROR = GAIN ACCURACY (FROM SPEC TABLE) + ADDITIONAL GAIN ERROR 6 INPUT COMMON-MODE VOLTAGE V. k SOURCE RESISTANCE MISMATCH TPC 9. Common-Mode Rejection vs. Input Common- Mode Voltage for Single-Supply Operation TPC. Additional Gain Error vs. Source Resistance Mismatch 6

8 AD66.6 QUIESCENT CURRENT ma... G = V PER VERTICAL DIVISION. SUPPLY VOLTAGE V TPC. Quiescent Supply Current vs. Supply Voltage for Single-Supply Operation SECONDS PER HORIZONTAL DIVISION TPC 6.. Hz to Hz RTI Voltage Noise. V S = ± V, Gain =. QUIESCENT CURRENT ma... CLOSED-LOOP GAIN 6 FOR V S = V AND +V SUPPLY VOLTAGE V TPC. Quiescent Supply Current vs. Supply Voltage for Dual-Supply Operation k k k M VALUE OF RESISTOR R G TPC 7. Closed-Loop Gain vs. R G VOLTAGE NSD V/ Hz.. GAIN =, V S = V DUAL SUPPLY POWER SUPPLY REJECTION db 6 SINGLE +PSRR ALL CURVES FOR GAINS OF OR SINGLE AND DUAL PSRR DUAL +PSRR. k k k FREQUENCY Hz. k FREQUENCY Hz k k M TPC. Noise Voltage Spectral Density vs. Frequency TPC. Power Supply Rejection vs. Frequency 7

9 AD % % TPC 9. Large Signal Pulse Response. V S = ± V, G = TPC. Large Signal Pulse Response. V S = + V, G = 9 9 % % TPC. Large Signal Pulse Response. V S = ± V, G = TPC. Settling Time. V S = ± V, G = mv 9 9 % % TPC. Large Signal Pulse Response. V S = + V, G = TPC. Settling Time. V S = ± V, G =

10 AD % % TPC. Settling Time. V S = + V, G = TPC 6. Settling Time. V S = + V, G = INPUT V p p k k k k AD66 k Figure. Settling Time Test Circuit ERROR THEORY OF OPERATION The AD66 is a differential amplifier con sist ing of a precision bal anced attenuator, a very low drift preamplifier (A), and an out put buffer amplifier (A). It has been designed so that small differential signals can be accurately am pli fied and filtered in the presence of large common -mode voltages (V CM ), without the use of any other active components. Figure shows the main elements of the AD66. The signal in puts at Pins and are first applied to dual resistive at ten u a tors R through R whose purpose is to reduce the peak com mon-mode voltage at the input to the preamplifier a feed back stage based on the very low drift op amp A. This allows the dif feren tial input voltage to be accurately amplified in the pres ence of large common-mode volt ag es six times greater than that which can be tol er at ed by the actual input to A. As a re sult, the in put CMR ex tends to six times the quantity (V S V). The over all common - mode error is min i mized by precise laser-trimming of R and R, thus giving the AD66 a common-mode re jec tion ra tio (CMRR) of at least,: ( db). To minimize the effect of spurious RF signals at the inputs due to rectification at the input to A, small filter capacitors C and C are included. The output of A is connected to the in put of A via a k (R) resistor to facilitate the low-pass filtering of the sig nal of in ter est (see Low-Pass Filtering section). The k input impedance of the AD66 requires that the source re sis tance driving this amplifier be low in val ue (< k ) this is R R C pf R k C pf R k A R9 k R k R7 9k AD66 A R k R k R6 R.k R7 R k R k R R k GND GAIN = Figure. Simplified Schematic 9

11 AD66 necessary to min i mize gain error. Also, any mis match be tween the total source re sis tance at each input will af fect gain ac cu ra cy and common -mode rejection (CMR). For ex am ple: when operating at a gain of, an mismatch in the source re sis tance between the inputs will degrade CMR to 6 db. The output buffer, A, operates at a gain of or, thus setting the overall, precalibrated gain of the AD66 (with no ex ter nal com po nents) at or. The gain is set by the feedback net work around amplifier A. The output of amplifier A relies on a k resistor to for pull-down. For single-supply operation, ( = GND ), A can drive a k ground ref er enced load to at least +.7 V. The min i mum, nominally zero, output voltage will be mv. For dual-supply op er a tion (± V), the positive output voltage swing will be the same as for a single supply. The negative swing will be to. V, at G =, limited by the ratio: R R VS + R + R + R The negative range can be extended to. V (G = ) and V (G = ) by add ing an external k pull-down from the out put to. This will add. ma to the AD66 s qui es cent cur rent, bringing the total to ma. The AD66 s khz bandwidth at G = and (a MHz gain bandwidth) is much higher than can be obtained with low power op amps in discrete dif fer en tial amplifier circuits. Fur ther - more, the AD66 is stable driving capacitive loads up to pf (G) or pf (G). Capacitive load drive can be increased to pf (G) by connecting a resistor in series with the AD66 s output and the load. ADJUSTING THE GAIN OF THE AD66 The AD66 is easily configured for gains of or. Figure shows that for a gain of, Pin 7 is simply left un con nect ed; similarly, for a gain of, Pin 7 is grounded, as shown in Fig ure 6. Gains between and are easily set by connecting a vari able resistance between Pin 7 and Analog GND, as shown in Fig ure 7. Because the on-chip resistors have an absolute tol er ance of ±% (although they are ratio matched to within.%), at least a % adjustment range must be provided. The values shown in the table in Figure 7 provide a good trade-off be tween gain set range and resolution, for gains from to 9. PUT PUT PUT PUT PUT. F ANALOG GND k AD66 /6 G = G = G = 7 6. F Figure 6. AD66 Configured for a Gain of. F CF (OPTIONAL) ANALOG GND k AD66 /6 G = R H CORNER FREQUENCY OF = CF (k ) GAIN RANGE R G ( ) R H ( ) G = k k k G = RESISTOR VALUES FOR GAIN ADJUSTMENT.99k 7 6 PUT R G. F PUT Figure 7. Recommended Circuit for Gain Adjustment SINGLE-POLE LOW-PASS ING A low-pass filter can be easily implemented by using the fea tures provided by the AD66. By simply connecting a capacitor between Pin and ground, a single-pole low-pass filter is created, as shown in Figure. PUT PUT ANALOG GND /6 G = G = 7 NOT CONNECTED PUT ANALOG GND /6 G = G = 7. F k AD66 G = 6. F PUT CF k AD66 G = 6. F +V PUT Figure. AD66 Configured for a Gain of CORNER FREQUENCY OF = CF (k ) Figure. A One-Pole Low-Pass Filter Circuit Which Operates from a Single + V Supply

12 AD66 CURRENT SENSOR INTERFACE A typical current sensing application, making use of the large common-mode range of the AD66, is shown in Figure 9. The cur rent being measured is sensed across resistor R S. The value of R S should be less than k and should be selected so that the average differential voltage across this resistor is typically mv. To produce a full-scale output of + V, a gain of is used adjustable by ±% to absorb the tolerance in the sense re sis tor. Note that there is sufficient headroom to allow at least a % over range (to +. V). CURRENT IN BRIDGE APPLICATION Figure shows the AD66 in a typical bridge application. Here, the AD66 is set to operate at a gain of, using dual-sup ply voltages and offering the option of low-pass filtering. ANALOG GND /6 G = G = 7 CURRENT CURRENT SENSOR R S ANALOG GND /6 G = G = 7 R H R G V. F CF OPTIONAL LOW-PASS k AD66 G = 6 +V. F PUT 6 Figure. A Typical Bridge Application. F CF OPTIONAL LOW-PASS k AD66 G =. F PUT Figure 9. Current Sensor Interface

13 AD66 LINE DIMENSIONS -Lead Standard Small Outline Package [SOIC] Narrow Body (R-) Dimensions shown in millimeters and (inches). (.7). (.97). (.96). (.9) 6. (.). (.) C7 /(D). (.9). (.) COPLANARITY..7 (.) BSC SEATING PLANE.7 (.6). (.). (.). (.). (.9).9 (.7). (.96). (.99).7 (.). (.6) COMPLIANT TO JEDEC STANDARDS MS-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 -Lead Plastic Dual-In Line Package [PDIP] (N-) Dimensions shown in inches and (millimeters).7 (9.).6 (9.7). (9.). (.7) MAX.9 (7.9). (7.).7 (6.9). (.) BSC. (.) MIN. (.). (.) SEATING PLANE. (.79).6 (.). (.6). (.7). (.6). (.). (.6). (.6). (7.7). (7.6). (.). (.). (.). (.). (.). (.) COMPLIANT TO JEDEC STANDARDS MO-9AA 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 Revision History Location Page / Data Sheet changed from REV. C to. Renumbered Figures and TPCs Universal Edits to Figure Edits to SPECIFICATIONS, Output Edit to ORDERING GUIDE Update to standard CAUTION/ESD Warning note and diagram Edits to TPC Updated LINE DIMENSIONS PRINTED IN U.S.A.

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