INA125PG4

INA 125 ® INA125 INA1 25 INSTRUMENTATION AMPLIFIER With Precision Voltage Reference FEATURES APPLICATIONS ● LOW QUIESCENT CURRENT: 460µA ● PRECISION VOLTAGE REFERENCE: 1.24V, 2.5V, 5V or 10V ● SLEEP MODE ● LOW OFFSET VOLTAGE: 250µV max ● PRESSURE AND TEMPERATURE BRIDGE AMPLIFIERS ● LOW OFFSET DRIFT: 2µV/°C max ● LOW INPUT BIAS CURRENT: 20nA max ● HIGH CMR: 100dB min ● BATTERY OPERATED SYSTEMS ● GENERAL PURPOSE INSTRUMENTATION ● INDUSTRIAL PROCESS CONTROL ● FACTORY AUTOMATION ● MULTI-CHANNEL DATA ACQUISITION SLEEP V+ ● LOW NOISE: 38nV/√ Hz at f = 1kHz ● INPUT PROTECTION TO ±40V 1 ● WIDE SUPPLY RANGE Single Supply: 2.7V to 36V Dual Supply: ±1.35V to ±18V 2 INA125 VREFCOM 12 R 13 VREFBG ● 16-PIN DIP AND SO-16 SOIC PACKAGES R 14 VREF2.5 DESCRIPTION 2R The INA125 is a low power, high accuracy instrumentation amplifier with a precision voltage reference. It provides complete bridge excitation and precision differential-input amplification on a single integrated circuit. A single external resistor sets any gain from 4 to 10,000. The INA125 is laser-trimmed for low offset voltage (250µV), low offset drift (2µV/°C), and high common-mode rejection (100dB at G = 100). It operates on single (+2.7V to +36V) or dual (±1.35V to ±18V) supplies. 15 VREF5 4R VREF10 16 4 10V The voltage reference is externally adjustable with pinselectable voltages of 2.5V, 5V, or 10V, allowing use with a variety of transducers. The reference voltage is accurate to ±0.5% (max) with ±35ppm/°C drift (max). Sleep mode allows shutdown and duty cycle operation to save power. The INA125 is available in 16-pin plastic DIP and SO-16 surface-mount packages and is specified for the –40°C to +85°C industrial temperature range. VREFOut Ref Amp Bandgap VREF + VIN 6 10 A1 VO 9 30kΩ RG 11 Sense 10kΩ 10kΩ + –) G VO = (VIN – VIN 8 7 – VIN G = 4 + 60kΩ RG A2 30kΩ IAREF 5 3 V– International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ©1997 Burr-Brown Corporation SBOS060 PDS-1361B Printed in U.S.A., February, 1998 SPECIFICATIONS: VS = ±15V At TA = +25°C, VS = ±15V, IA common = 0V, VREF common = 0V, and RL = 10kΩ, unless otherwise noted. INA125P, U PARAMETER CONDITIONS INPUT Offset Voltage, RTI Initial vs Temperature vs Power Supply Long-Term Stability Impedance, Differential Common-Mode Safe Input Voltage Input Voltage Range Common-Mode Rejection VS = ±1.35V to ±18V, G = 4 INA125PA, UA TYP MAX ±50 ±0.25 ±3 ±0.2 1011 || 2 1011 || 9 ±250 ±2 ±20 MIN TYP MAX UNITS ✻ ✻ ✻ ✻ ✻ ✻ ±500 ±5 ±50 µV µV/°C µV/V µV/mo Ω || pF Ω || pF V ±40 ✻ ✻ See Text VCM = –10.7V to +10.2V G=4 G = 10 G = 100 G = 500 BIAS CURRENT vs Temperature Offset Current vs Temperature VCM = 0V NOISE, RTI Voltage Noise, f = 10Hz f = 100Hz f = 1kHz f = 0.1Hz to 10Hz Current Noise, f = 10Hz f = 1kHz f = 0.1Hz to 10Hz RS = 0Ω GAIN Gain Equation Range of Gain Gain Error MIN 78 86 100 100 84 94 114 114 10 ±60 ±0.5 ±0.5 72 80 90 90 ✻ ✻ ✻ ✻ 25 ±2.5 50 ±5 nA pA/°C nA pA/°C nV/√Hz nV/√Hz nV/√Hz µVp-p fA/√Hz fA/√Hz pAp-p ✻ 4 + 60kΩ/RG VO = –14V to +13.3V G=4 G = 10 G = 100 G = 500 dB dB dB dB ✻ ✻ ✻ ✻ ✻ ✻ ✻ 40 38 38 0.8 170 56 5 4 ✻ ✻ ✻ ✻ 10,000 ✻ V/V V/V ✻ ±0.01 ±0.03 ±0.05 ±0.1 ±0.075 ±0.3 ±0.5 ✻ ✻ ✻ ✻ ±0.1 ±0.5 ±1 % % % % ±1 ±25 ±15 ±100 ✻ ✻ ✻ ✻ ppm/°C ppm/°C ±0.0004 ±0.0004 ±0.001 ±0.002 ±0.002 ±0.002 ±0.01 ✻ ✻ ✻ ✻ ±0.004 ±0.004 ✻ Gain vs Temperature G=4 G > 4(1) VO = –14V to +13.3V G=4 G = 10 G = 100 G = 500 Nonlinearity OUTPUT Voltage: Positive Negative Load Capacitance Stability Short-Circuit Current VOLTAGE REFERENCE Accuracy vs Temperature vs Power Supply, V+ vs Load Dropout Voltage, (V+) – VREF(2) Bandgap Voltage Reference Accuracy vs Temperature (V+)–1.7 (V–)+1 VREF = +2.5V, +5V, +10V IL = 0 IL = 0 V+ = (VREF + 1.25V) to +36V IL = 0 to 5mA Ref Load = 2kΩ 1.25 IL = 0 IL = 0 ✻ ✻ (V+)–0.9 (V–)+0.4 1000 –9/+12 ±0.15 ±18 ±20 3 1 1.24 ±0.5 ±18 ±0.5 ±35 ±50 75 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ % % % % of of of of FS FS FS FS V V pF mA ±1 ±100 ±100 ✻ % ppm/°C ppm/V ppm/mA V V % ppm/°C 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. ® INA125 2 SPECIFICATIONS: VS = ±15V (CONT) At TA = +25°C, VS = ±15V, IA common = 0V, VREF common = 0V, and RL = 10kΩ, unless otherwise noted. INA125P, U PARAMETER CONDITIONS FREQUENCY RESPONSE Bandwidth, –3dB Slew Rate Settling Time, 0.01% Overload Recovery POWER SUPPLY Specified Operating Voltage Specified Voltage Range Quiescent Current, Positive Negative Reference Ground Current(3) Sleep Current (VSLEEP ≤ 100mV) MIN G=4 G = 10 G = 100 G = 500 G = 4, 10V Step G = 4, 10V Step G = 10, 10V Step G = 100, 10V Step G = 500, 10V Step 50% Overdrive INA125PA, UA MAX MIN IO = IREF = 0mA IO = IREF = 0mA ±15 460 –280 180 ±1 RL = 10kΩ, Ref Load = 2kΩ +2.7 0 ✻ ✻ ✻ ✻ ✻ ±25 V+ +0.1 –40 –55 –55 MAX ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ V V µA µA µs ✻ ✻ ✻ °C °C °C °C/W °C/W ✻ ✻ 80 100 V V µA µA µA µA ✻ ✻ ✻ ✻ ✻ +85 +125 +125 UNITS kHz kHz kHz kHz V/µs µs µs µs µs µs ✻ ±18 525 –325 15 0 150 TEMPERATURE RANGE Specification Range Operation Range Storage Range Thermal Resistance, θJA 16-Pin DIP SO-16 Surface-Mount TYP ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ 150 45 4.5 0.9 0.2 60 83 375 1700 5 ±1.35 SLEEP MODE PIN(4) VIH (Logic high input voltage) VIL (Logic low input voltage) IIH (Logic high input current) IIL (Logic low input current) Wake-up Time(5) TYP ✻ Specification same as INA125P, U. NOTES: (1) Temperature coefficient of the "Internal Resistor" in the gain equation. Does not include TCR of gain-setting resistor, RG. (2) Dropout voltage is the positive supply voltage minus the reference voltage that produces a 1% decrease in reference voltage. (3) VREFCOM pin. (4) Voltage measured with respect to Reference Common. Logic low input selects Sleep mode. (5) IA and Reference, see Typical Performance Curves. SPECIFICATIONS: VS = +5V At TA = +25°C, VS = +5V, IA common at VS /2, VREF common = VS /2, VCM = VS/2, and RL = 10kΩ to VS/2, unless otherwise noted. INA125P, U PARAMETER INPUT Offset Voltage, RTI Initial vs Temperature vs Power Supply Input Voltage Range Common-Mode Rejection GAIN Gain Error CONDITIONS VS = +2.7V to +36V VCM = +1.1V to +3.6V G=4 G = 10 G = 100 G = 500 78 86 100 100 VO = +0.3V to +3.8V G=4 OUTPUT Voltage, Positive Negative POWER SUPPLY Specified Operating Voltage Operating Voltage Range Quiescent Current Sleep Current (VSLEEP ≤ 100mV) MIN INA125PA, UA TYP MAX ±75 ±0.25 3 See Text ±500 MIN 20 84 94 114 114 72 80 90 90 ±0.01 (V+)–1.2 (V–)+0.3 ✻ ✻ (V+)–0.8 (V–)+0.15 IO = IREF = 0mA RL = 10kΩ, Ref Load = 2kΩ 460 ±1 MAX UNITS ✻ ✻ ✻ ✻ ±750 µV µV/°C µV/V 50 ✻ ✻ ✻ ✻ dB dB dB dB ✻ % ✻ ✻ V V ✻ +5 +2.7 TYP +36 525 ±25 ✻ ✻ ✻ ✻ ✻ ✻ V V µA µA ✻ Specification same as INA125P, U. ® 3 INA125 ABSOLUTE MAXIMUM RATINGS(1) PIN CONFIGURATION Top View 16-Pin DIP, SO-16 V+ 1 16 VREF10 SLEEP 2 15 VREF5 V– 3 14 VREF2.5 VREFOUT 4 13 VREFBG IAREF 5 12 VREFCOM + VIN 6 11 Sense – VIN 7 10 VO RG 8 9 Power Supply Voltage, V+ to V– ........................................................ 36V Input Signal Voltage .......................................................................... ±40V Output Short Circuit ................................................................. Continuous Operating Temperature ................................................. –55°C to +125°C Storage Temperature ..................................................... –55°C to +125°C Lead Temperature (soldering, 10s) ............................................... +300°C NOTE: Stresses above these ratings may cause permanent damage. PACKAGE INFORMATION RG PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) INA125PA INA125P 16-Pin Plastic DIP 16-Pin Plastic DIP 180 180 INA125UA INA125U SO-16 Surface-Mount SO-16 Surface-Mount 265 265 NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ELECTROSTATIC DISCHARGE SENSITIVITY 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. ® INA125 4 TYPICAL PERFORMANCE CURVES At TA = +25°C and VS = ±15V, unless otherwise noted. COMMON-MODE REJECTION vs FREQUENCY GAIN vs FREQUENCY 60 120 G = 500 Common-Mode Rejection (dB) G = 100, 500 50 G = 100 Gain (dB) 40 30 G = 10 20 G=4 10 80 G = 10 60 G = 500 G=4 40 G = 100 20 0 0 1 10 100 1k 10k 100k 1M 1 10 100 1k 10k 100k Frequency (Hz) Frequency (Hz) POSITIVE POWER SUPPLY REJECTION vs FREQUENCY NEGATIVE POWER SUPPLY REJECTION vs FREQUENCY 140 1M 120 120 Power Supply Rejection (dB) Power Supply Rejection (dB) 100 G = 500 100 G = 100 80 G=4 60 G = 10 40 100 G = 100 80 G = 500 60 40 G = 10 20 G=4 20 0 10 100 1k 10k 1M 1 100 1k 10k 100k INPUT COMMON-MODE VOLTAGE vs OUTPUT VOLTAGE, VS = ±15V INPUT COMMON-MODE VOLTAGE vs OUTPUT VOLTAGE, VS = ±5V 10 5 VD/2 0 – + VD/2 VO IAREF – + VCM –5 +15V + –15V –10 tput swing—see Limited by A2 ou text IAREF = 0V 4 –5 0 5 10 15 2 text VS = +5V 1 0 –1 VS = ±5V –2 –3 –4 tput swing—see Limited by A2 ou –5 Output Voltage (V) tput swing—see Limited by A2 ou 3 –5 –10 1M 5 text tput swing—see Limited by A2 ou –15 –15 10 Frequency (Hz) 15 Input Common-Mode Voltage (V) 100k Frequency (Hz) Input Common-Mode Voltage (V) 1 –4 –3 –2 –1 0 1 2 text 3 4 5 Output Voltage (V) ® 5 INA125 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C and VS = ±15V, unless otherwise noted. SETTLING TIME vs GAIN 10k 1k Current Noise 100 100 Voltage Noise 10 10 1 1 10 100 1k Settling Time (µs) 1k Input Bias Current Noise (fA/√Hz) Input-Referred Voltage Noise (nV/√Hz) INPUT-REFERRED VOLTAGE AND CURRENT NOISE vs FREQUENCY 1 1k INPUT-REFERRED OFFSET VOLTAGE vs SLEEP TURN-ON TIME QUIESCENT CURRENT AND SLEEP CURRENT vs TEMPERATURE 60 Quiescent and Sleep Current (µA) Offset Voltage Change (µV) 100 Gain (V/V) 80 G = 100 40 20 0 –20 –40 –60 –80 –100 50 100 150 200 550 500 450 400 350 +IQ 300 250 200 150 100 50 0 –50 250 ±ISLEEP –IQ VSLEEP = 100mV +ISLEEP VSLEEP = 0V –ISLEEP –75 –50 –25 0 25 50 75 Time From Turn-On (µs) Temperature (°C) SLEW RATE vs TEMPERATURE INPUT BIAS AND OFFSET CURRENT vs TEMPERATURE 0.30 100 125 100 125 Input Bias and Offset Current (nA) 16 0.25 Slew Rate (V/µs) 10 Frequency (Hz) 100 0 0.1% 100 10 1 100k 10k 0.01% 1k 0.20 0.15 0.10 0.05 0 14 12 10 8 IB 6 4 IOS 2 0 –75 –50 –25 0 25 50 75 100 125 –75 Temperature (°C) –25 0 25 50 Temperature (°C) ® INA125 –50 6 75 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C and VS = ±15V, unless otherwise noted. LARGE-SIGNAL RESPONSE SMALL-SIGNAL RESPONSE G=4 5V/div 200mV/div G=4 G = 100 G = 100 100µs/div 100µs/div INPUT BIAS CURRENT vs INPUT OVERLOAD VOLTAGE INPUT-REFERRED NOISE, 0.1Hz to 10Hz 200 200nV/div Input Bias Current (µA) 160 All Gains 120 80 40 0 –40 –80 –120 –160 –200 –40 1µs/div 0 40 Overload Voltage (V) OUTPUT VOLTAGE SWING vs OUTPUT CURRENT DELTA VOS vs REFERENCE CURRENT 25 +75°C 20 +25°C +125°C (V+)–3 (V+)–4 (V+)–5 Delta VOS, RTI (µV) Output Voltage (V) V+ (V+)–1 (V+)–2 –55°C (V–)+5 (V–)+4 +75°C (V–)+3 (V–)+2 (V–)+1 –55°C Sinking 15 10 5 Sourcing 0 +125°C +25°C V– –5 0 ±2 ±4 ±6 ±8 –8 ±10 Output Current (mA) –6 –4 –2 0 2 4 6 8 Reference Current (mA) ® 7 INA125 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C and VS = ±15V, unless otherwise noted. INPUT-REFERRED OFFSET VOLTAGE PRODUCTION DISTRIBUTION, VS = ±15V INPUT-REFERRED OFFSET VOLTAGE PRODUCTION DISTRIBUTION, VS = +5V 30 35 Typical production distribution of packaged units. 20 15 10 0.1% 5 0.02% 25 20 15 10 0.02% 0.1% 0.05% 0 –500 –450 –400 –350 –300 –250 –200 –150 –100 –50 0 50 100 150 200 250 300 350 400 450 500 –750 –675 –600 –525 –450 –375 –300 –225 –150 –75 0 75 150 225 300 375 450 525 600 675 750 0 Input-Referred Offset Voltage (µV) Input-Referred Offset Voltage (µV) VOLTAGE REFERENCE DRIFT PRODUCTION DISTRIBUTION INPUT-REFERRED OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION 100 40 30 0.2% 100 0.05% 10 ±4.00 ±3.75 ±3.50 ±3.25 ±3.00 ±2.75 ±2.50 ±2.25 ±2.00 ±1.75 ±1.50 ±1.25 0 ±1.00 0 ±0.75 10 ±0.50 10 ±0.25 0.3% 20 90 20 50 80 30 60 50 40 70 40 VS = ±15V or +5V 30 60 80 20 70 50 Typical production distribution of packaged units. 90 Percent of Amplifiers (%) 80 70 Typical production distribution of packaged units. 60 90 Percent of Amplifiers (%) 0.1% 5 0.1% 0.02% Typical production distribution of packaged units. 30 Percent of Amplifiers (%) Percent of Amplifiers (%) 25 Voltage Reference Drift (ppm/°C) Input-Referred Offset Voltage Drift (µV/°C) REFERENCE VOLTAGE DEVIATION vs TEMPERATURE REFERENCE TURN-ON SETTLING TIME 50 Reference Voltage Deviation (ppm) 15 12 Reference Error (%) 9 6 4 0 –3 VREF = 10V –6 VREF = 5V –9 –12 VREF = 2.5V 10 20 30 40 50 –100 –150 –50 –25 0 25 50 Temperature (°C) Time From Power Supply Turn-On (µs) ® INA125 –50 –200 –75 –15 0 VREF = VBG, 2.5V, 5V, or 10V 0 8 75 100 125 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C and V S = ±15V, unless otherwise noted. 0.1Hz to 10Hz REFERENCE NOISE VREF = 2.5V, CL = 100pF 1mA/div REFERENCE TRANSIENT RESPONSE VREF = 2.5V, CL = 100pF +1mA 0mA 50mV/div Reference Output 2µV/div –1mA 1µs/div 10µs/div NEGATIVE REFERENCE AC LINE REJECTION vs FREQUENCY POSITIVE REFERENCE AC LINE REJECTION vs FREQUENCY 120 VREF = 2.5V 100 VREF = 5V Negative AC Line Rejection (dB) Positive AC Line Rejection (dB) 120 80 VREF = 10V C = 0.01µF 60 C = 0.1µF 40 Capacitor connected between VREFOUT and VREFCOM. 20 VREF = 2.5V 100 VREF = 5V 80 VREF = 10V 60 40 20 0 0 1 10 100 1k 10k 100k 1 1M 10 100 1k 10k 100k 1M Frequency (Hz) Frequency (Hz) ® 9 INA125 APPLICATION INFORMATION For example, in Figure 1 VREFOUT is connected to VREF10 thus supplying 10V to the bridge. It is recommended that VREFOUT be connected to one of the reference voltage pins even when the reference is not being utilized to avoid saturating the reference amplifier. Driving the SLEEP pin LOW puts the INA125 in a shutdown mode. Figure 1 shows the basic connections required for operation of the INA125. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins as shown. The output is referred to the instrumentation amplifier reference (IAREF) terminal which is normally grounded. This must be a low impedance connection to assure good common-mode rejection. A resistance of 12Ω in series with the IAREF pin will cause a typical device to degrade to approximately 80dB CMR (G = 4). SETTING THE GAIN Gain of the INA125 is set by connecting a single external resistor, RG, between pins 8 and 9: G =4+ Connecting VREFOUT (pin 4) to one of the four available reference voltage pins (VREFBG, VREF2.5, VREF5, or VREF10) provides an accurate voltage source for bridge applications. 60kΩ RG (1) Commonly used gains and RG resistor values are shown in Figure 1. V+ SLEEP(1) 0.1µF 2 1 DESIRED GAIN (V/V) RG (Ω) NEAREST 1% RG VALUE (Ω) 4 5 10 20 50 100 200 500 1000 2000 10000 NC 60k 10k 3750 1304 625 306 121 60 30 6 NC 60.4k 10k 3740 1300 619 309 121 60.4 30.1 6.04 INA125 VREFCOM 12 R(2) 13 VREFBG R 14 VREF2.5 2R 15 VREF5 4R VREF10 16 NC: No Connection. 4 10V VREFOut Ref Amp Bandgap VREF + – V –) G VO = (VIN IN G = 4 + 60kΩ RG + VIN 6 10 A1 9 30kΩ Sense 10kΩ RG 11 + 10kΩ Load 8 7 – VIN A2 30kΩ IAREF 5 NOTE: (1) SLEEP pin should be connected to V+ if shutdown function is not being used. (2) Nominal value of R is 21kΩ, ±25%. 3 0.1µF V– FIGURE 1. Basic Connections. ® INA125 10 VO – INPUT COMMON-MODE RANGE The 60kΩ term in equation 1 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 INA125. The input common-mode range of the INA125 is shown in the typical performance curves. The common-mode range is limited on the negative side by the output voltage swing of A2, an internal circuit node that cannot be measured on an external pin. The output voltage of A2 can be expressed as: V = 1.3V – – (V + – V – ) (10kΩ/R ) The stability and temperature drift of the external gain setting resistor, RG, also affects gain. RG’s contribution to gain accuracy and drift can be directly inferred from the gain equation (1). Low resistor values required for high gain can make wiring resistance important. Sockets add to the wiring resistance, which will contribute additional gain error (possibly an unstable gain error) in gains of approximately 100 or greater. 02 V+ The on-board precision voltage reference provides an accurate voltage source for bridge and other transducer applications or ratiometric conversion with analog-to-digital converters. A reference output of 2.5V, 5V or 10V is available by connecting VREFOUT (pin 4) to one of the VREF pins (VREF2.5, VREF5, or VREF10). Reference voltages are lasertrimmed for low inital error and low temperature drift. Connecting VREFOUT to VREFBG (pin 13) produces the bandgap reference voltage (1.24V ±0.5%) at the reference output. 100µA 1/2 REF200 IAREF IN OPA237 10kΩ G PRECISION VOLTAGE REFERENCE V+ VO INA125 IN The internal op amp A2 is identical to A1. Its output swing is limited to approximately 0.8V from the positive supply and 0.25V from the negative supply. When the input common-mode range is exceeded (A2’s output is saturated), A1 can still be in linear operation, responding to changes in the non-inverting input voltage. The output voltage, however, will be invalid. The INA125 is laser trimmed for low offset voltage and offset voltage drift. Most applications require no external offset adjustment. Figure 2 shows an optional circuit for trimming the output offset voltage. The voltage applied to the IAREF terminal is added to the output signal. The op amp buffer is used to provide low impedance at the IAREF terminal to preserve good common-mode rejection. RG IN (voltages referred to IAREF terminal, pin 5) OFFSET TRIMMING – VIN IN Positive supply voltage must be 1.25V above the desired reference voltage. For example, with V+ = 2.7V, only the 1.24V reference (VREFBG) can be used. If using dual supplies VREFCOM can be connected to V–, increasing the 100Ω ±10mV Adjustment Range 100Ω 100µA 1/2 REF200 Microphone, Hydrophone etc. INA125 V– FIGURE 2. Optional Trimming of Output Offset Voltage. 47kΩ 47kΩ INPUT BIAS CURRENT RETURN The input impedance of the INA125 is extremely high— approximately 1011Ω. However, a path must be provided for the input bias current of both inputs. This input bias current flows out of the device and is approximately 10nA. High input impedance means that this input bias current changes very little with varying input voltage. Thermocouple INA125 10kΩ Input circuitry must provide a path for this input bias current for proper operation. Figure 3 shows various provisions for an input bias current path. Without a bias current path, the inputs will float to a potential which exceeds the commonmode range, and the input amplifiers will saturate. INA125 If the differential source resistance is low, the bias current return path can be connected to one input (see the thermocouple example in Figure 3). 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. Center-tap provides bias current return. FIGURE 3. Providing an Input Common-Mode Current Path. ® 11 INA125 A transition region exists when VSLEEP is between 400mV and 2.7V (with respect to VREFCOM) where the output is unpredictable. Operation in this region is not recommended. The INA125 achieves high accuracy quickly following wakeup (VSLEEP ≥ 2.7V). See the typical performance curve “Input-Referred Offset Voltage vs Sleep Turn-on Time.” If shutdown is not being used, connect the SLEEP pin to V+. amount of supply voltage headroom available to the reference. Approximately 180µA flows out of the VREFCOM terminal, therefore, it is recommended that it be connected through a low impedance path to sensor common to avoid possible ground loop problems. Reference noise is proportional to the reference voltage selected. With VREF = 2.5V, 0.1Hz to 10Hz peak-to-peak noise is approximately 9µVp-p. Noise increases to 36µVp-p for the 10V reference. Output drive capability of the voltage reference is improved by connecting a transistor as shown in Figure 4. The external transistor also serves to remove power from the INA125. LOW VOLTAGE OPERATION The INA125 can be operated on power supplies as low as ±1.35V. Performance remains excellent with power supplies ranging from ±1.35V to ±18V. 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. See “Input Common-Mode Voltage Range.” As previously mentioned, when using the on-board reference with low supply voltages, it may be necessary to connect VREFCOM to V– to ensure VS – VREF ≥ 1.25V. Internal resistors that set the voltage reference output are ratio-trimmed for accurate output voltages (±0.5% max). The absolute resistance values, however, may vary ±25%. Adjustment of the reference output voltage with an external resistor is not recommended because the required resistor value is uncertain. VREFCOM INA125 SINGLE SUPPLY OPERATION 12 The INA125 can be used on single power supplies of +2.7V to +36V. Figure 5 shows a basic single supply circuit. The IAREF, VREFCOM, and V– terminals are connected to ground. Zero differential input voltage will demand an output voltage of 0V (ground). When the load is referred to ground as shown, actual output voltage swing is limited to approximately 150mV above ground. The typical performance curve “Output Voltage Swing vs Output Current” shows how the output swing varies with output current. 13 VREFBG VREF2.5 VREF5 VREF10 14 15 With single supply operation, careful attention should be paid to input common-mode range, output voltage swing of both op amps, and the voltage applied to the IAREF terminal. VIN+ and VIN– must both be 1V above ground for linear operation. You cannot, for instance, connect the inverting input to ground and measure a voltage connected to the noninverting input. 16 V+ 4 TIP29C VREFOut Ref Amp Bandgap VREF 10V to load (transducer) +3V +3V FIGURE 4. Reference Current Boost. 1.5V – ∆V SHUTDOWN 1000Ω The INA125 has a shutdown option. When the SLEEP pin is LOW (100mV or less), the supply current drops to approximately 1µA and output impedance becomes approximately 80kΩ. Best performance is achieved with CMOS logic. To maintain low sleep current at high temperatures, VSLEEP should be as close to 0V as possible. This should not be a problem if using CMOS logic unless the CMOS gate is driving other currents. Refer to the typical performance curve, “Sleep Current vs Temperature.” 1.5V + ∆V 12 VO INA125 12 5 3 FIGURE 5. Single Supply Bridge Amplifier. ® INA125 RG RL INPUT PROTECTION The inputs of the INA125 are individually protected for voltage up to ±40V. For example, a condition of –40V on one input and +40V on the other input will not cause damage. Internal circuitry on each input provides low series impedance under normal signal conditions. To provide equivalent protection, series input resistors would contribute excessive noise. If the input is overloaded, the protection circuitry limits the input current to a safe value of approximately 120µA to 190µA. The typical performance curve “Input Bias Current vs Input Overload Voltage” shows this input current limit behavior. The inputs are protected even if the power supplies are disconnected or turned off. SLEEP +5V 2 1 INA125 VREFCOM 12 VREFBG VREF2.5 VREF5 13 14 15 16 VREF10 4 Ref Amp Bandgap VREF 2.5V + VIN 6 10 A1 9 30kΩ Sense 10kΩ RG 11 + 10kΩ Load 8 7 – VIN + – VO = +2.5V + [(VIN – VIN ) (4 + 60kΩ )] RG A2 30kΩ IAREF – 5 3 2.5V(1) (Psuedoground) NOTE: (1) “Psuedoground” is at +2.5V above actual ground. This provides a precision reference voltage for succeeding single-supply op amp stages. FIGURE 6. Psuedoground Bridge Measurement, 5V Single Supply. ® 13 INA125 PACKAGE OPTION ADDENDUM www.ti.com 7-Oct-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) INA125P ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type -40 to 85 INA125P INA125PA ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type INA125P A INA125PAG4 ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type INA125P A INA125U ACTIVE SOIC D 16 40 RoHS & Green Call TI Level-3-260C-168 HR INA125U A INA125U/2K5 ACTIVE SOIC D 16 2500 RoHS & Green Call TI Level-3-260C-168 HR INA125U A INA125UA ACTIVE SOIC D 16 40 RoHS & Green Call TI Level-3-260C-168 HR INA125U A INA125UA/2K5 ACTIVE SOIC D 16 2500 RoHS & Green Call TI Level-3-260C-168 HR INA125U A (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of