INA138&168

® INA138 INA168 ©1999 Burr-Brown Corporation PDS-1576A Printed in U.S.A. December, 1999 FEATURES l COMPLETE UNIPOLAR HIGH-SIDE CURRENT MEASUREMENT CIRCUIT l WIDE SUPPLY AND COMMON-MODE RANGE l INA138: 2.7V to 36V l INA168: 2.7V to 60V l INDEPENDENT SUPPLY AND INPUT COMMON-MODE VOLTAGES l SINGLE RESISTOR GAIN SET l LOW QUIESCENT CURRENT (25µA typ) l SOT23-5 Package High-Side Measurement CURRENT SHUNT MONITOR DESCRIPTION The INA138 and INA168 are high-side, unipolar, current shunt monitors. Wide input common-mode voltage range, low quiescent current, and tiny SOT-23 packaging enable use in a variety of applications. Input common-mode and power supply voltages are independent and can range from 2.7V to 36V for the INA138 and 2.7V to 60V for the INA168. Both models draw only 25µA quiescent current, which also permits connecting the power supply to either side of the current measurement shunt with minimal error. The device converts a differential input voltage to a current output. This current is converted back to a voltage with an external load resistor that sets any gain from 1 to over 100. Although designed for current shunt measurement, the circuit invites creative applications in measurement and level shifting. Both the INA138 and INA168 are available in SOT23-5 and are specified for the –40°C to +85°C industrial temperature range. APPLICATIONS l CURRENT SHUNT MEASUREMENT Automotive, Telephone, Computers l PORTABLE & BATTERY BACKUP SYSTEMS l BATTERY CHARGERS l POWER MANAGEMENT l CELL PHONES l PRECISION CURRENT SOURCE 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/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 For most current data sheet and other product information, visit www.burr-brown.com RS 2 1 OUT GND RL VO = ISRSRL/5kΩ Load 5kΩ 5kΩ VIN+ VIN+ VIN– 3 4 IS V+ 5 2 ® INA138, INA168 SPECIFICATIONS At TA = –40°C to +85°C, VS = 5V, VIN+ = 12V, ROUT = 125kΩ, unless otherwise noted. PARAMETER CONDITION MIN TYP MAX MIN TYP MAX UNITS INPUT Full-Scale Sense Voltage VSENSE = VIN+ – VIN– 100 500 ] ] mV Common-Mode Input Range 2.7 36 ] 60 V Common-Mode Rejection VIN+ = 2.7V to 40V, VSENSE = 50mV 100 120 dB VIN+ = 2.7V to 60V, VSENSE = 50mV 100 120 dB Offset Voltage(1) ±0.2 ±1 ] ] mV vs Temperature TMIN to TMAX 1 ] µV/°C vs Power Supply V– = 2.7V to 40V, VSENSE = 50mV 0.1 10 µV/V V– = 2.7V to 60V, VSENSE = 50mV 0.1 10 µV/V Input Bias Current VIN+ , VIN– 2 ] uA OUTPUT Transconductance VSENSE = 10mV – 150mV 198 200 202 ] ] ] µA/V vs Temperature VSENSE = 100mV 10 ] nA/°C Nonlinearity Error VSENSE = 10mV to 150mV ±0.01 ±0.1 ] ] % Total Output Error VSENSE = 100mV ±0.5 ±2 ] ] % Output Impedance 1 || 5 ] GΩ || pF Voltage Output Swing to Power Supply, V+ (V+) – 0.8 (V+) – 1.0 ] ] V Swing to Common Mode, VCM VCM – 0.5 VCM – 0.8 ] ] V FREQUENCY RESPONSE Bandwidth ROUT = 5kΩ 800 ] kHz ROUT = 125kΩ 32 ] kHz Settling Time (0.1%) 5V Step, ROUT = 5kΩ 1.8 ] µs 5V Step, ROUT = 125kΩ 30 ] µs NOISE Output-Current Noise Density 9 ] pA/√Hz Total Output-Current Noise BW = 100kHz 3 ] nA RMS POWER SUPPLY Operating Range, V+ 2.7 36 ] 60 V Quiescent Current VSENSE = 0, IO = 0 25 45 ] ] µA TEMPERATURE RANGE Specification, TMIN to TMAX –40 85 ] ] °C Operating –55 125 ] ] °C Storage –65 150 ] ] °C Thermal Resistance θJA 200 ] °C/W NOTES: (1) Defined as the amount of input voltage, VSENSE, to drive the output to zero. INA138 INA168 3 ® INA138, INA168 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. 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. Supply Voltage, V+ INA138 ............................................................................... –0.3V to 60V INA168 ............................................................................... –0.3V to 60V Analog Inputs, VIN+ , VIN– INA138 Common Mode ............................................................... –0.3V to 40V Differential (VIN+ ) – (VIN– ) ..................................................... –40V to 2V INA168 Common Mode ............................................................... –0.3V to 60V Differential (VIN+ ) – (VIN– ) ..................................................... –40V to 2V Analog Output, Out .............................................................. –0.3V to 40V Operating Temperature ..................................................–55°C to +125°C Storage Temperature ..................................................... –55°C to +125°C Junction Temperature .................................................................... +150°C Lead Temperature (soldering, 10s) ............................................... +300°C NOTE: (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not implied. ABSOLUTE MAXIMUM RATINGS(1) PACKAGE SPECIFIED DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT PRODUCT PACKAGE NUMBER RANGE MARKING NUMBER(1) MEDIA INA138NA SOT-23-5 Surface Mount 331 –40°C to +85°C INA138NA/250 Tape and Reel " " " " " INA138NA/3K Tape and Reel INA168NA(2) SOT-23-5 Surface Mount 331 –40°C to +85°C INA168NA/250 Tape and Reel " " " " " INA168NA/3K Tape and Reel NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /3K indicates 3000 devices per reel). Ordering 3000 pieces of “INA138NA/3K” will get a single 3000-piece Tape and Reel. (2) INA168 available Q2'00. PACKAGE/ORDERING INFORMATION PIN CONFIGURATION TOP VIEW SOT OUT GND VIN V+ VIN 1 2 3 5 4+ – 4 ® INA138, INA168 TYPICAL PERFORMANCE CURVES At TA = +25°C, V+ = 5V, VIN+ = 12V, RL = 125kΩ, unless otherwise noted. 40 30 20 10 0 –10 –20 100 1k 10k 100k 1M 10M G ai n (dB ) Frequency (Hz) GAIN vs FREQUENCY RL = 50kΩ RL = 500kΩ CL = 10nF CL = 1nF CL = 100pF RL = 5kΩ 120 100 80 60 40 20 0 0.1 1 10 100 1k 10k Co m m on -M od e Re jec tio n ( dB ) Frequency (Hz) 100k G = 1 G = 10 G = 100 COMMON-MODE REJECTION vs FREQUENCY 140 120 100 80 60 40 20 1 10 100 1k 10k 100k Po w er -S up pl y Re jec tio n ( dB ) Frequency (Hz) POWER-SUPPLY REJECTION vs FREQUENCY G = 1 G = 10 G = 100 5 0 –5 –10 –15 0 25 50 75 100 125 To ta l O ut pu t E rro r ( %) VIN (mV) TOTAL OUTPUT ERROR vs VIN 150 200 –55°C +25°C +150°C VIN = (VIN – VIN)+ – 2 1 0 –1 –2 0 10 20 30 40 50 To ta l O ut pu t E rro r ( %) Power-Supply Voltage (V) TOTAL OUTPUT ERROR vs POWER-SUPPLY VOLTAGE 60 70 G = 1 G = 10 G = 25 Output error is essentially independent of both V+ supply voltage and input common-mode voltage. 50 40 30 20 10 0 0 10 20 30 40 50 Qu ies ce nt C ur re nt (µ A) Power-Supply Voltage (V) QUIESCENT CURRENT vs POWER-SUPPLY VOLTAGE 60 70 +150° +125° +25° –55° Use INA168 with (V+) > 36V 5 ® INA138, INA168 TYPICAL PERFORMANCE CURVES (Cont.) At TA = +25°C, V+ = 5V, VIN+ = 12V, RL = 125kΩ, unless otherwise noted. STEP RESPONSE 10µs/div 200mV G = 1 100mV 100mV G = 1 0mV 50mV/div STEP RESPONSE 10µs/div G = 25 0V G = 10 0V 1V/div 500mV/div 6 ® INA138, INA168 OPERATION Figure 1 shows the basic circuit diagram for both the INA138 and INA168. Load current, IS, is drawn from supply, VS, through shunt resistor, Rs. The voltage drop in the shunt resistor, VS, is forced across Rg1 by the internal op-amp, causing current to flow into the collector of Q1. External resistor, RL, converts the output current to a volt- age, VOUT, at the Out pin. The transfer function for the INA138 is: IO = gm (VIN+ – VIN– ) (1) where gm = 200µA/V (2) In the circuit of Figure 1, the input voltage, (VIN+ – VIN– ), is equal to IS • RS and the output voltage, VOUT, is equal to IO • RL. The transconductance, gm, of the INA138 is 200µA/V. The complete transfer function for the current measurement amplifier in this application is: VOUT = (IS) (RS) (200µA/V) (RL) (3) The maximum differential input voltage for accurate mea- surements is 0.5V, which produces a 100µA output current. A differential input voltage of up to 2V will not cause damage. Differential measurements (pins 3 and 4) must be unipolar with a more-positive voltage applied to pin 3. If a more-negative voltage is applied to pin 3, the output current, IO, will be zero, but it will not cause damage. BASIC CONNECTION Figure 1 shows the basic connection of the INA138. The input pins, VIN+ and VIN– , should be connected as closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance. The output resistor, RL, is shown connected between pin 1 and ground. Best accuracy is achieved with the output voltage measured directly across RL. This is especially important in high-current systems where load current could flow in the ground connections, affecting the measurement accuracy. No power supply bypass capacitors are required for stability of the INA138. However, applications with noisy or high impedance power supplies may require de-coupling capaci- tors to reject power supply noise. Connect bypass capacitors close to the device pins. POWER SUPPLIES The input circuitry of the INA138 can accurately measure beyond its power supply voltage, V+. For example, the V+ power supply can be 5V while the load power supply is voltage is up to +36V (or +60V with INA168). However, the output voltage range of the Out terminal is limited by the lesser of the two voltages (see “Output Voltage Range”). SELECTING RS AND RL The value chosen for the shunt resistor, RS, depends on the application and is a compromise between small-signal accu- racy and maximum permissible voltage loss in the measure- ment line. High values of RS provide better accuracy at FIGURE 1. Basic Circuit Connections. Shunt RS INA138 2 1 OUT Q1 RL I0 + VO – Load RG1 5kΩ RG2 5kΩ VIN VIN 3 4 IS V+ 5 NOTE: (1) Maximum VP and V+ voltage is 60V with INA168. V+ power can be common or indepedent of load supply. 2.7 ≤ (V+) ≤ 36V(1) VP Load Power Supply +2.7 to 36V(1) + – VOLTAGE GAIN EXACT RL (Ω) NEAREST 1% RL (Ω) 1 5k 4.99k 2 10k 10k 5 25k 24.9k 10 50k 49.9k 20 100k 100k 50 250k 249k 100 500k 499k 7 ® INA138, INA168 lower currents by minimizing the effects of offset, while low values of RS minimize voltage loss in the supply line. For most applications, best performance is attained with an RS value that provides a full-scale shunt voltage of 50mV to 100mV. Maximum input voltage for accurate measurements is 500mV. RL is chosen to provide the desired full-scale output voltage. The output impedance of the INA138 Out terminal is very high which permits using values of RL up to 500kΩ with excellent accuracy. The input impedance of any additional circuitry at the output should be much higher than the value of RL to avoid degrading accuracy. Some A/D converters have input impedances that will sig- nificantly affect measurement gain. The input impedance of the A/D converter can be included as part of the effective RL if its input can be modeled as a resistor to ground. Alterna- tively, an op-amp can be used to buffer the A/D converter input. See Figure 1 for recommended values of RL. OUTPUT VOLTAGE RANGE The output of the INA138 is a current, which is converted to a voltage by the load resistor, RL. The output current remains accurate within the compliance voltage range of the output circuitry. The shunt voltage and the input common-mode and power supply voltages limit the maximum possible output swing. The maximum output voltage compliance is limited by the lower of the two equations below: Vout max = (V+) – 0.7V – (VIN+ – VIN– ) (4) or Vout max = VIN– – 0.5V (5) (whichever is lower) BANDWIDTH Measurement bandwidth is affected by the value of the load resistor, RL. High gain produced by high values of RL will yield a narrower measurement bandwidth (see Typical Per- formance Curves). For widest possible bandwidth, keep the capacitive load on the output to a minimum. Reduction in bandwidth due to capacitive load is shown in the Typical Performance Curves. If bandwidth limiting (filtering) is desired, a capacitor can be added to the output, as shown in Figure 3. This will not cause instability. APPLICATIONS The INA138 is designed for current shunt measurement circuits as shown in Figure 1, but its basic function is useful in a wide range of circuitry. A creative engineer will find many unforeseen uses in measurement and level shifting circuits. A few ideas are shown. FIGURE 2. Buffering Output to Drive A/D Converter. IS OPA340 INA138 3 4 ZIN RL Buffer of amp drives A/D converter without affecting gain. FIGURE 3. Output Filter. INA138 f –3dB = 1 2piRLCL VO f –3dB RL CL 3 4 FIGURE 4. Offsetting the Output Voltage. V0 R2 R1 1 Gain Set by R1//R2 Output Offset = (V+)R2 R1+R2 a). Using resistor divider. V0 RL 1 REF200 100µA V+V+ Gain Set by RL Output Offset = (100µA)(RL) (independent of V+) b). Using current source. INA138 3 4 INA138 3 4