INA (R) INA2128 212 INA 8 212 8 Dual, Low Power INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION LOW OFFSET VOLTAGE: 50V max The INA2128 is a dual, low power, general purpose instrumentation amplifier offering excellent accuracy. Its versatile 3-op amp design and small size make it ideal for a wide range of applications. Current-feedback input circuitry provides wide bandwidth even at high gain (200kHz at G = 100). LOW DRIFT: 0.5V/C max LOW INPUT BIAS CURRENT: 5nA max HIGH CMR: 120dB min INPUTS PROTECTED TO 40V WIDE SUPPLY RANGE: 2.25V to 18V A single external resistor sets any gain from 1 to 10,000. Internal input protection can withstand up to 40V without damage. LOW QUIESCENT CURRENT: 700A / IA 16-PIN PLASTIC DIP, SOL-16 The INA2128 is laser trimmed for very low offset voltage (50V), drift (0.5V/C) and high commonmode rejection (120dB at G 100). It operates with power supplies as low as 2.25V, and quiescent current is only 700A per IA--ideal for battery operated and multiple-channel systems. APPLICATIONS SENSOR AMPLIFIER THERMOCOUPLE, RTD, BRIDGE MEDICAL INSTRUMENTATION MULTIPLE-CHANNEL SYSTEMS The INA2128 is available in 16-pin plastic DIP, and SOL-16 surface-mount packages, specified for the -40C to +85C temperature range. BATTERY OPERATED EQUIPMENT V+ 9 - VINA 1 Over-Voltage Protection INA2128 7 A1A 40k 3 40k 25k A3A RGA 4 2 Over-Voltage Protection - 16 Over-Voltage Protection VINB 14 5 A2A 40k 40k 40k 40k 13 15 GB = 1 + 25k A3B + RefA 10 A1B RGB VINB VOA 25k + VINA 6 GA = 1 + 50k RGA 11 50k RGB VOB 25k Over-Voltage Protection 12 A2B 40k RefB 40k 8 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 (c) 1994 Burr-Brown Corporation PDS-1243C Printed in U.S.A. January, 1996 SPECIFICATIONS At TA = +25C, VS = 15V, RL = 10k, unless otherwise noted. INA2128P, U PARAMETER CONDITIONS INPUT Offset Voltage, RTI Initial TA = +25C vs Temperature TA = TMIN to TMAX vs Power Supply VS = 2.25V to 18V Long-Term Stability Impedance, Differential Common-Mode VO = 0V Common-Mode Voltage Range(1) Safe Input Voltage Common-Mode Rejection VCM = 13V, RS = 1k G=1 G=10 G=100 G=1000 TYP MAX 50 500/G 0.5 20/G 1 100/G (V+) - 2 (V-) + 2 10 100/G 0.2 2/G 0.2 20/G 0.1 3/G 1010 || 2 1011 || 9 (V+) - 1.4 (V-) + 1.7 80 100 120 120 86 106 125 130 2 30 1 30 BIAS CURRENT vs Temperature Offset Current vs Temperature NOISE VOLTAGE, RTI f = 10Hz f = 100Hz f = 1kHz fB = 0.1Hz to 10Hz Noise Current f=10Hz f=1kHz fB = 0.1Hz to 10Hz INA2128PA, UA MIN 40 73 93 110 110 5 5 G=1 G=10 G=100 G=1000 G=1 VO = 13.6V, G=1 G=10 G=100 G=1000 OUTPUT Voltage: Positive Negative Load Capacitance Stability Short-Circuit Current RL = 10k RL = 10k (V+) - 1.4 (V-) + 1.4 MAX 25 100/G 125 1000/G 0.2 5/G 1 20/G 2 200/G UNITS V V/C V/V V/mo || pF || pF V V V dB dB dB dB 10 10 nA pA/C nA pA/C 10 8 8 0.2 nV/Hz nV/Hz nV/Hz Vp-p 0.9 0.3 30 pA/Hz pA/Hz pAp-p 1 + (50k/RG) 1 TYP G = 1000, RS = 0 GAIN Gain Equation Range of Gain Gain Error Gain vs Temperature(2) 50k Resistance(2, 3) Nonlinearity MIN 0.01 0.02 0.05 0.5 1 25 0.0001 0.0003 0.0005 0.001 10000 0.024 0.4 0.5 1 10 100 0.001 0.002 0.002 (Note 4) (V+) - 0.9 (V-) + 0.8 1000 +6/-15 0.1 0.5 0.7 2 0.002 0.004 0.004 V/V V/V % % % % ppm/C ppm/C % of FSR % of FSR % of FSR % of FSR V V pF mA MHz kHz kHz kHz V/s s s s s s FREQUENCY RESPONSE Bandwidth, -3dB Overload Recovery G=1 G=10 G=100 G=1000 VO = 10V, G=10 G=1 G=10 G=100 G=1000 50% Overdrive POWER SUPPLY Voltage Range Current, Total VIN = 0V Slew Rate Settling Time, 0.01% 1.3 700 200 20 4 7 7 9 80 4 2.25 TEMPERATURE RANGE Specification Operating JA 15 1.4 -40 -40 80 18 1.5 85 125 V mA C C C/W Specification same as INA2128P, U. NOTE: (1) Input common-mode range varies with output voltage--see typical curves. (2) Guaranteed by wafer test. (3) Temperature coefficient of the "50k" term in the gain equation. (4) Nonlinearity measurements in G = 1000 are dominated by noise. Typical nonlinearity is 0.001%. 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. (R) INA2128 2 ELECTROSTATIC DISCHARGE SENSITIVITY PIN CONFIGURATION Top View DIP SOL-16 - VINA 1 - 16 VINB + VINA 2 + 15 VINB RGA 3 14 RGB RGA 4 13 RGB RefA 5 12 RefB VOA 6 11 VOB SenseA 7 10 SenseB V- 8 9 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. V+ ORDERING INFORMATION ABSOLUTE MAXIMUM RATINGS Supply Voltage .................................................................................. 18V Analog Input Voltage Range ............................................................. 40V Output Short-Circuit (to ground) .............................................. Continuous Operating Temperature ................................................. -40C to +125C Storage Temperature ..................................................... -40C to +125C Junction Temperature .................................................................... +150C Lead Temperature (soldering, 10s) ............................................... +300C PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) INA2128PA INA2128P INA2128UA INA2128U 16-Pin Plastic DIP 16-Pin Plastic DIP SOL-16 Surface-Mount SOL-16 Surface-Mount 180 180 211 211 TEMPERATURE RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (R) 3 INA2128 TYPICAL PERFORMANCE CURVES At TA = +25C, VS = 15V, unless otherwise noted. COMMON-MODE REJECTION vs FREQUENCY GAIN vs FREQUENCY 140 60 G = 1000V/V G = 100V/V G = 1000V/V Common-Mode Rejection (dB) 50 40 Gain (dB) G = 100V/V 30 20 G = 10V/V 10 0 G = 1V/V -10 1k 10k 100k 1M G = 1V/V 80 60 40 20 10 10M 100 1k 100k 10k Frequency (Hz) Frequency (Hz) POSITIVE POWER SUPPLY REJECTION vs FREQUENCY NEGATIVE POWER SUPPLY REJECTION vs FREQUENCY 140 120 120 Power Supply Rejection (dB) 140 G = 1000V/V 100 G = 100V/V 80 60 G = 10V/V 40 G = 1V/V 1M G = 1000V/V G = 100V/V 100 80 60 40 G = 10V/V 20 20 0 0 G = 1V/V 10 15 100 1k 10k 100k 10 1M 100k INPUT COMMON-MODE RANGE vs OUTPUT VOLTAGE, VS = 5, 2.5V G=1 G=1 VD/2 VD/2 + +15V - VO + - Ref + VCM -15V -10 3 2 G=1 0 5 10 1 0 G=1 -1 -2 -3 -5 -5 15 Output Voltage (V) VS = 5V VS = 2.5V -4 -3 -2 -1 0 1 Output Voltage (V) (R) INA2128 G=1 G 10 -4 -5 G 10 G 10 4 5 0 1M 5 G 10 -10 10k INPUT COMMON-MODE RANGE vs OUTPUT VOLTAGE, VS = 15V 10 -15 -15 1k Frequency (Hz) G 10 -5 100 Frequency (Hz) Common-Mode Voltage (V) Power Supply Rejection (dB) G = 10V/V 100 0 -20 Common-Mode Voltage (V) 120 4 2 3 4 5 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = 15V, unless otherwise noted. CROSSTALK vs FREQUENCY INPUT- REFERRED NOISE vs FREQUENCY 120 G = 10V/V Crosstalk (dB) 100 G = 1V/V G = 1000V/V 80 G = 100V/V 60 40 20 0 G = 1V/V 10 100 G = 10V/V 1 10 G = 100, 1000V/V Current Noise 0.1 1 10 100 1k 100k 10k 1M 1 10 QUIESCENT CURRENT and SLEW RATE vs TEMPERATURE Quiescent Current (A) 0.1% 1.7 6 1.6 5 1.5 1 1.4 3 IQ 1.3 2 10 100 -75 1000 -50 -25 Gain (V/V) INPUT OVER-VOLTAGE V/I CHARACTERISTICS 8 Input Current (mA) Flat region represents normal linear operation. Offset Voltage Change (V) 4 G = 1000V/V 1 G = 1V/V 0 +15V G = 1V/V 1/2 INA2128 -2 -3 VIN 25 50 75 100 IIN 6 4 2 0 -2 -4 -6 -8 -15V -5 -10 -50 -40 -30 -20 -10 0 10 1 125 OFFSET VOLTAGE WARM-UP 10 G = 1000V/V 0 Temperature (C) 5 -4 4 Slew Rate 1.2 1 -1 10k SETTLING TIME vs GAIN 10 2 1k Frequency (Hz) 0.01% 3 100 Frequency (Hz) 100 Settling Time (s) 100 Input Bias Current Noise (pA/ Hz) G = 100V/V 1k Slew Rate (V/s) G = 1000V/V Input-Referred Voltage Noise (nV/ Hz) 140 20 30 40 50 0 Input Voltage (V) 10 20 30 40 50 Time (ms) (R) 5 INA2128 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = 15V, unless otherwise noted. OUTPUT VOLTAGE SWING vs OUTPUT CURRENT INPUT BIAS CURRENT vs TEMPERATURE (V+) 2 1 Output Voltage (V) Input Bias Current (nA) (V+)-0.4 IB IOS 0 Typical IB and IOS Range 2nA at 25C -1 (V+)-0.8 (V+)-1.2 (V+)+1.2 (V-)+0.8 (V-)+0.4 -2 V- -50 -25 0 25 50 75 100 0 125 4 SHORT-CIRCUIT OUTPUT CURRENT vs TEMPERATURE Short Circuit Current (mA) 14 +25C +85C (V+)-0.8 -40C RL = 10k (V-)+1.2 +25C -40C (V-)+0.4 3 OUTPUT VOLTAGE SWING vs POWER SUPPLY VOLTAGE (V+)-0.4 (V-)+0.8 2 Output Current (mA) 16 (V+)-1.2 1 Temperature (C) V+ +85C -40C +85C -ISC 12 10 8 6 4 +ISC 2 V- 0 0 5 10 15 20 -75 -25 0 25 50 75 100 Temperature (C) MAXIMUM OUTPUT VOLTAGE vs FREQUENCY TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 125 1 G = 10, 100 25 -50 Power Supply Voltage (V) 30 VO = 1Vrms 500kHz Measurement Bandwidth G=1 G=1 RL = 10k G = 1000 20 THD+N (%) Peak-to-Peak Output Voltage (Vpp) Output Voltage Swing (V) -75 15 10 0.1 G = 100, RL = 100k 0.01 G = 1, RL = 100k 5 Dashed Portion is noise limited. 0 1k 10k 100k 0.001 100 1M Frequency (Hz) 10k Frequency (Hz) (R) INA2128 1k 6 G = 10V/V RL = 100k 100k TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = 15V, unless otherwise noted. SMALL-SIGNAL STEP RESPONSE (G = 1, 10) SMALL-SIGNAL STEP RESPONSE (G = 100, 1000) G=1 G = 100 20mV/div 20mV/div G = 10 G = 1000 5s/div 20s/div LARGE-SIGNAL STEP RESPONSE (G = 1, 10) LARGE-SIGNAL STEP RESPONSE (G = 100, 1000) G=1 G = 100 5V/div 5V/div G = 10 G = 1000 5s/div 5s/div VOLTAGE NOISE 0.1 to 10Hz INPUT-REFERRED, G 100 0.1V/div 1s/div (R) 7 INA2128 APPLICATION INFORMATION Figure 1 shows the basic connections required for operation of the INA2128. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins as shown. internal feedback resistors of A1 and A2. These on-chip metal film resistors 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 INA2128. The output is referred to the output reference (Ref) terminals (RefA and RefB) which are normally grounded. These must be low-impedance connections to assure good commonmode rejection. A resistance of 8 in series with a Ref pin will cause a typical device to degrade to approximately 80dB CMR (G = 1). 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 in gains of approximately 100 or greater. The INA2128 has a separate output sense feedback connections SenseA and SenseB. These must be connected to their respective output terminals for proper operation. The output sense connection can be used to sense the output voltage directly at the load for best accuracy. DYNAMIC PERFORMANCE The typical performance curve "Gain vs Frequency" shows that despite its low quiescent current, the INA2128 achieves wide bandwidth, even at high gain. This is due to its currentfeedback topology. Settling time also remains excellent at high gain--see "Settling Time vs Gain." SETTING THE GAIN Gain of the INA2128 is set by connecting a single external resistor, RG, connected as shown: G = 1+ 50k RG NOISE PERFORMANCE (1) The INA2128 provides very low noise in most applications. Low frequency noise is approximately 0.2Vp-p measured from 0.1 to 10Hz (G 100). This provides dramatically improved noise when compared to state-of-the-art chopperstabilized amplifiers. Commonly used gains and resistor values are shown in Figure 1. The 50k term in equation 1 comes from the sum of the two V+ 0.1F Pin numbers for Channel B shown in parenthesis. - VIN 1 (16) 9 INA2128 Over-Voltage Protection 40k 3 RG () 1 2 5 10 20 50 100 200 500 1000 2000 5000 10000 NC 50.00k 12.50k 5.556k 2.632k 1.02k 505.1 251.3 100.2 50.05 25.01 10.00 5.001 NC 49.9k 12.4k 5.62k 2.61k 1.02k 511 249 100 49.9 24.9 10 4.99 6 (11) A3 + 4 25k Load VO (13) + VIN 2 (15) - Ref A2 Over-Voltage Protection 40k 8 40k 5 (12) 0.1F V- Also drawn in simplified form: - VIN NC: No Connection. RG INA2128 Ref + VIN FIGURE 1. Basic Connections. (R) INA2128 G=1+ RG NEAREST 1% RG () 40k 25k (14) DESIRED GAIN 7 Sense + - (10) ) VO = G * (VIN - VIN A1 8 VO NOTE: If channel is unused, connect inputs to ground, sense to VO, and leave Ref open-circuit. 50k RG OFFSET TRIMMING The INA2128 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 Ref terminal is summed with the output. The op amp buffer provides low impedance at the Ref terminal to preserve good common-mode rejection. Microphone, Hydrophone etc. 1/2 INA2128 47k 47k 1/2 INA2128 Thermocouple - VIN RG + VIN V+ 1/2 INA2128 10k VO 100A 1/2 REF200 Ref OPA177 10k 100 (For other channel) 1/2 INA2128 10mV Adjustment Range 100 Center-tap provides bias current return. 100A 1/2 REF200 FIGURE 3. Providing an Input Common-Mode Current Path. V- INPUT BIAS CURRENT RETURN PATH voltage swing of amplifiers A1 and A2. So the linear common-mode input range is related to the output voltage of the complete amplifier. This behavior also depends on supply voltage--see performance curves "Input Common-Mode Range vs Output Voltage." The input impedance of the INA2128 is extremely high-- approximately 1010. However, a path must be provided for the input bias current of both inputs. This input bias current is approximately 2nA. High input impedance means that this input bias current changes very little with varying input voltage. Input-overload can produce an output voltage that appears normal. For example, if an input overload condition drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output amplifier will be near zero. The output of the INA2128 will be near 0V even though both inputs are overloaded. FIGURE 2. Optional Trimming of Output Offset Voltage. 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 of the INA2128 and the input amplifiers will saturate. LOW VOLTAGE OPERATION The INA2128 can be operated on power supplies as low as 2.25V. Performance remains excellent with power supplies ranging from 2.25V 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 assure that the input voltages remain within their linear range. Voltage swing requirements of internal nodes limit the input commonmode range with low power supply voltage. Typical performance curves, "Input Common-Mode Range vs Output Voltage" show the range of linear operation for 15V, 5V, and 2.5V supplies. 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. INPUT COMMON-MODE RANGE The linear input voltage range of the input circuitry of the INA2128 is from approximately 1.4V below the positive supply voltage to 1.7V above the negative supply. As a differential input voltage causes the output voltage increase, however, the linear input range will be limited by the output (R) 9 INA2128 INPUT PROTECTION The inputs of the INA2128 are individually protected for voltages 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 1.5 to 5mA. The typical performance curve "Input Bias Current vs Common-Mode Input Voltage" shows this input current limit behavior. The inputs are protected even if the power supplies are disconnected or turned off. CHANNEL CROSSTALK The two channels of the INA2128 are completely independent, including all bias circuitry. At DC and low frequency there is virtually no signal coupling between channels. Crosstalk increases with frequency and is dependent on circuit gain, source impedance and signal characteristics. As source impedance increases, careful circuit layout will help achieve lowest channel crosstalk. Most crossstalk is produced by capacitive coupling of signals from one channel to the input section of the other channel. To minimize coupling, separate the input traces as far as practical from any signals associated with the opposite channel. A grounded guard trace surrounding the inputs helps reduce stray coupling between channels. Run the differential inputs of each channel parallel to each other or directly adjacent on top and bottom side of a circuit board. Stray coupling then tends to produce a common-mode signal which is rejected by the IA's input. VEX X-axis X-axis VO 1/2 INA2128 V1 VO = GA (V2 - V1) + GB (V4 - V3) 1/2 INA2128 RGA VEX Ref V2 V3 Y-axis Y-axis VO 1/2 INA2128 1/2 INA2128 RGB Ref V4 FIGURE 5. Sum of Differences Amplifier. FIGURE 4. Two-Axis Bridge Amplifier. RG = 5.6k 2.8k LA RA RG/2 1/2 INA2128 VO Ref 2.8k 390k 1/2 OPA2604 RL VG 1/2 OPA2604 10k 390k FIGURE 6. ECG Amplifier With Right-Leg Drive. (R) INA2128 10 G = 10 VG NOTE: Due to the INA2128's current-feedback topology, VG is approximately 0.7V less than the common-mode input voltage. This DC offset in this guard potential is satisfactory for many guarding applications.