Single Supply, MicroPower INSTRUMENTATION AMPLIFIER

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1 Single Supply, MicroPower INSTRUMENTATION AMPLIFIER FEATURES LOW QUIESCENT CURRENT: µa WIDE POWER SUPPLY RANGE Single Supply:. to Dual Supply:.9/. to ± COMMON-MODE RANGE TO (). RAIL-TO-RAIL OUTPUT SWING LOW OFFSET OLTAGE: µ max LOW OFFSET DRIFT: µ/ C max LOW NOISE: n/ Hz LOW INPUT BIAS CURRENT: na max -PIN DIP AND SO- SURFACE-MOUNT IN IN kω kω kω kω O k G = O = ( IN IN ) G APPLICATIONS PORTABLE, BATTERY OPERATED SYSTEMS INDUSTRIAL SENSOR AMPLIFIER: Bridge, RTD, Thermocouple PHYSIOLOGICAL AMPLIFIER: ECG, EEG, EMG MULTI-CHANNEL DATA ACQUISITION DESCRIPTION The is a precision instrumentation amplifier for accurate, low noise differential signal acquisition. Its two-op-amp design provides excellent performance with very low quiescent current, and is ideal for portable instrumentation and data acquisition systems. The can be operated with single power supplies from. to and quiescent current is a mere µa. It can also be operated from dual supplies. By utilizing an input level-shift network, input commonmode range extends to. below negative rail (single supply ground). A single external resistor sets gain from / to /. Laser trimming provides very low offset voltage (µ max), offset voltage drift (µ/ C max) and excellent common-mode rejection. Package options include -pin plastic DIP and SO- surface-mount packages. Both are specified for the C to C extended industrial temperature range. International Airport Industrial Park Mailing Address: PO Box, Tucson, AZ Street Address: S. Tucson Blvd., Tucson, AZ Tel: () - Twx: 9-9- Internet: FAXLine: () - (US/Canada Only) Cable: BBRCORP Telex: -9 FAX: () 9- Immediate Product Info: () - 99 Burr-Brown Corporation PDS-B Printed in U.S.A. October, 99

2 SPECIFICATIONS At T A = C, S =, R L = kω connected to S /, unless otherwise noted. P, U PA, UA PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS INPUT Offset oltage, RTI ± ± ± ± µ vs Temperature ± ± ± µ/ C vs Power Supply (PSRR) S =. to µ/ Input Impedance Ω pf Safe Input oltage R S = (). (). R S = kω () () Common-Mode oltage Range. Common-Mode Rejection CM = to. 9 9 db INPUT BIAS CURRENT na vs Temperature ± pa/ C Offset Current ± ± ± na vs Temperature ± pa/ C GAIN G = to k / Gain Equation G = kω/ / Gain Error G = ±. ±. ±. % vs Temperature G = ppm/ C Gain Error G = ±. ±. ± % vs Temperature G = ± ± ppm/ C Nonlinearity G =, O =. to.9 ±. ±. ±. % NOISE (RTI) oltage Noise, f = khz n/ Hz f = Hz n/ Hz f = Hz n/ Hz f B =.Hz to Hz µp-p Current Noise, f = khz fa/ Hz f B =.Hz to Hz pap-p OUTPUT oltage, Positive S = ± (). (). Negative S = ± (). (). Short-Circuit Current Short-Circuit to Ground / ma Capacitive Load Drive nf FREQUENCY RESPONSE Bandwidth, db G = khz G = khz G =.9 khz Slew Rate./. /µs Settling Time,.% G = µs G = µs G =. ms Overload Recovery % Input Overload µs POWER SUPPLY oltage Range, Single Supply. Dual Supplies.9/. ± Current I O = µa TEMPERATURE RANGE Specification C Operation C Storage C Thermal Resistance, θ JA -Pin DIP C/W SO- Surface-Mount C/W Specification same as P, U. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.

3 PIN CONFIGURATION Top iew -Pin DIP, SO- ELECTROSTATIC DISCHARGE SENSITIITY IN IN O This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ABSOLUTE MAXIMUM RATINGS () Supply oltage, to... Signal Input Terminals, oltage ()... (). to (). Current ()... ma Output Short Circuit... Continuous Operating Temperature... C to C Storage Temperature... C to C Lead Temperature (soldering, s)... C NOTES: () Stresses above these ratings may cause permanent damage. () Input terminals are internally diode-clamped to the power supply rails. Input signals that can exceed the supply rails by more than. should be current-limited to ma or less. PACKAGE INFORMATION PACKAGE DRAWING PRODUCT PACKAGE NUMBER () PA -Pin DIP P -Pin DIP UA SO- Surface Mount U SO- Surface Mount NOTE: () For detailed drawing and dimension table, see end of data sheet, or Appendix C of Burr-Brown IC Data Book.

4 TYPICAL PERFORMANCE CURES At T A = C and S = ±, unless otherwise noted. Gain (db) GAIN vs FREQUENCY G = G = G = G = k k k M Common-Mode Rejection (db) COMMON-MODE REJECTION vs FREQUENCY 9 G = G = G = k k k POSITIE POWER SUPPLY REJECTION vs FREQUENCY G = NEGATIE POWER SUPPLY REJECTION vs FREQUENCY Power Supply Rejection (db) G = G = Power Supply Rejection (db) G = G = G = k k k M k k k INPUT COMMON-MODE RANGE vs OUTPUT OLTAGE, S = ±, G = INPUT COMMON-MODE OLTAGE vs OUTPUT OLTAGE, S = ±, G = Common-Mode oltage () D/ D/ CM O Limited by A output swing see text Input Common-Mode oltage () S = ± Limited by A output swing see text S = / REF =. REF = Output oltage () Output oltage ()

5 TYPICAL PERFORMANCE CURES (CONT) At T A = C and S = ±, unless otherwise noted. OLTAGE and CURRENT NOISE DENSITY vs FREQUENCY (RTI) SETTLING TIME vs GAIN oltage Noise (n/ Hz) Current Noise (fa/ Hz) N I N Settling Time (ms) Step.%.% k k. k Gain (/) Offset oltage Change (µ) INPUT-REFERRED OFFSET OLTAGE WARM-UP Turn-on time ms. Settling time to final value depends on Gain see settling time. 9 Time After Turn-On (ms) (Noise) Quiescent Current (µa) QUIESCENT CURRENT vs TEMPERATURE Temperature ( C) TOTAL HARMONIC DISTORTIONNOISE vs FREQUENCY OUTPUT OLTAGE SWING vs OUTPUT CURRENT () Sourcing Current THDN (%).. G = G = R L = R L = kω Output oltage () () () () Sinking Current. k k Output Current (ma)

6 TYPICAL PERFORMANCE CURES (CONT) At T A = C and S = ±, unless otherwise noted. SMALL-SIGNAL STEP RESPONSE G = SMALL-SIGNAL STEP RESPONSE G = m/div m/div µs/div µs/div LARGE-SIGNAL STEP RESPONSE G = INPUT-REFERRED NOISE OLTAGE.Hz to Hz /div µ/div µs/div ms/div

7 APPLICATION INFORMATION Figure shows the basic connections required for operation of the. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins. The output is referred to the output reference () terminal which is normally grounded. This must be a low-impedance connection to ensure good common-mode rejection. A resistance of Ω in series with the pin will cause a typical device to degrade to approximately db CMR. SETTING THE GAIN Gain of the is set by connecting a single external resistor,, as shown: kω () G = Commonly used gains and resistor values are shown in Figure. The kω term in equation comes from the internal metal film resistors which are laser trimmed to accurate absolute values. The accuracy and temperature coefficient of these resistors are included in the gain accuracy and drift specifications of the. The stability and temperature drift of the external gain setting resistor,, also affects gain. s contribution to gain accuracy and drift can be directly inferred from the gain equation (). OFFSET TRIMMING The is laser trimmed for low offset voltage and offset voltage drift. Most applications require no external offset adjustment. Figure shows an optional circuit for trimming the output offset voltage. The voltage applied to the terminal is added to the output signal. An op amp buffer is used to provide low impedance at the terminal to preserve good common-mode rejection. IN IN FIGURE. Optional Trimming of Output Offset oltage. INPUT BIAS CURRENT RETURN PATH The input impedance of the is extremely high approximately Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is approximately na (current flows out of the input terminals). High input impedance means that this input bias current changes very little with varying input voltage. O OPA ±m Adjustment Range kω µa / REF Ω Ω µa / REF DESIRED GAIN NEAREST % (/) (Ω) ALUE NC NC k.k.k.k.. IN.µF A kω kω kω Load G = kω O = ( IN IN ) G O NC: No Connection. Also drawn in simplified form: A IN kω IN IN O Single Supply.µF Dual Supply FIGURE. Basic Connections.

8 Input circuitry must provide a path for this input bias current for proper operation. Figure shows various provisions for an input bias current path. Without a bias current path, the inputs will float to a potential which exceeds the common-mode range of the and the input amplifiers will saturate. If the differential source resistance is low, the bias current return path can be connected to one input (see the thermocouple example in Figure ). With higher source impedance, using two equal resistors provides a balanced input with possible advantages of lower input offset voltage due to bias current and better high-frequency common-mode rejection. Microphone, Hydrophone etc. Thermocouple kω kω kω Center-tap provides bias current return. FIGURE. Providing an Input Common-Mode Current Path. INPUT PROTECTION The inputs of the are protected with internal diodes connected to the power supply rails (Figure ). These diodes will clamp the applied signal to prevent it from damaging the input circuitry. If the input signal voltage can exceed the power supplies by more than., the input signal current should be limited to less than ma to protect the internal clamp diodes. This can generally be done with a series input resistor. Some signal sources are inherently current-limited and do not require limiting resistors. INPUT COMMON-MODE RANGE The common-mode range for some common operating conditions is shown in the typical performance curves. The can operate over a wide range of power supply and REF configurations, making it impractical to provide a comprehensive guide to common-mode range limits for all possible conditions. The most commonly overlooked overload condition occurs by attempting to exceed the output swing of A, an internal circuit node that cannot be measured. Calculating the expected voltages at A s output (see equation in Figure ) provides a check for the most common overload conditions. The design of A and A are identical and their outputs can swing to within approximately m of the power supply rails, depending on load conditions. When A s output is saturated, A can still be in linear operation, responding to changes in the non-inverting input voltage. This may give the appearance of linear operation but the output voltage is invalid. A single supply instrumentation amplifier has special design considerations. Using commonly available single-supply op amps to implement the two-op amp topology will not yield equivalent performance. For example, consider the condition where both inputs of common single-supply op amps are IN. IN () () A kω O kω kω O =. IN ( IN kω IN ). () (oltages are referred to REF ) A (). (). IN () IN. kω FIGURE. Simplified Circuit Diagram.

9 equal to. The outputs of both A and A must be. But any small positive voltage applied to IN requires that A s output must swing below, which is clearly impossible without a negative power supply. To achieve common-mode range that extends to singlesupply ground, the uses precision level-shifting buffers on its inputs. This shifts both inputs by approximately., and through the feedback network, shifts A s output by approximately.. With both inputs and REF at single-supply, A s output is well within its linear range. A positive IN causes A s output to swing below.. As a result of this input level-shifting, the voltages at pin and pin are not equal to their respective input terminal voltages (pins and ). For most applications, this is not important since only the gain-setting resistor connects to these pins. LOW OLTAGE OPERATION The can be operated on a single power supply as low as. (or a total of. on dual supplies). Performance remains excellent throughout the power supply range up to (or ±). Most parameters vary only slightly throughout this supply voltage range see typical performance curves. Operation at very low supply voltage requires careful attention to ensure that the common-mode voltage remains within its linear range. LOW QUIESCENT CURRENT OPERATION The maintains its low quiescent current (µa) while the output is within linear operation (up to m from the supply rails). When the input creates a condition that overdrives the output into saturation, quiescent current increases. With O overdriven into the positive rail, the quiescent current increases to approximately µa. Likewise, with O overdriven into the negative rail (single supply ground) the quiescent current increases to approximately µa. OUTPUT CURRENT RANGE Output sourcing and sinking current values versus the output voltage ranges are shown in the typical performance curves. The positive and negative current limits are not equal. Positive output current sourcing will drive moderate to high load impedances. Battery operation normally requires the careful management of power consumption to keep load impedances very high throughout the design. CM m REF µa kω m IN O =. to.9 O IN (µa) () NOTE: () To accomodate bipolar input signals, REF can be offset to a positive voltage. Output voltage is then referred to the voltage applied to. FIGURE. Micropower Single Supply Bridge Amplifier. Load Shunt R S.Ω I L.A m IN IN G = kω.µf REF IN IN ADS -Bit A/D D CS CLK Serial Data Chip Select Clock Differential measurement avoids ground loop errors. FIGURE. Single-Supply Current Shunt Measurement. 9

10 This datasheet has been downloaded from: Datasheets for electronic components.

Precision INSTRUMENTATION AMPLIFIER

Precision INSTRUMENTATION AMPLIFIER FEATURES LOW OFFSET VOLTAGE: µv max LOW DRIFT:.µV/ C max LOW INPUT BIAS CURRENT: na max HIGH COMMON-MODE REJECTION: db min INPUT OVER-VOLTAGE PROTECTION: ±V WIDE SUPPLY