® INA138 INA168 For most current data sheet and other product information, visit www.burr-brown.com High-Side Measurement CURRENT SHUNT MONITOR FEATURES DESCRIPTION ● COMPLETE UNIPOLAR HIGH-SIDE CURRENT MEASUREMENT CIRCUIT ● WIDE SUPPLY AND COMMON-MODE RANGE ● INA138: 2.7V to 36V ● INA168: 2.7V to 60V ● INDEPENDENT SUPPLY AND INPUT COMMON-MODE VOLTAGES ● SINGLE RESISTOR GAIN SET ● LOW QUIESCENT CURRENT (25µA typ) ● SOT23-5 PACKAGE The INA138 and INA168 are high-side, unipolar, current shunt monitors. Wide input common-mode voltage range, low quiescent current, and tiny SOT23 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. Quiescent current is only 25µA, which 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. APPLICATIONS ● CURRENT SHUNT MEASUREMENT: Automotive, Telephone, Computers ● PORTABLE & BATTERY-BACKUP SYSTEMS ● BATTERY CHARGERS ● POWER MANAGEMENT ● CELL PHONES ● PRECISION CURRENT SOURCE Both the INA138 and INA168 are available in SOT23-5 and are specified for the –40°C to +85°C industrial temperature range. IS RS VIN+ Up To 60V 4 3 VIN+ VIN– 5kΩ Load 5kΩ V+ 5 OUT GND 2 VO = ISRSRL/5kΩ 1 RL 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 ©1999 Burr-Brown Corporation SBOS122 PDS-1576B Printed in U.S.A. August, 2000 SPECIFICATIONS At TA = –40°C to +85°C, VS = 5V, VIN+ = 12V, ROUT = 125kΩ, unless otherwise noted. INA138NA PARAMETER CONDITION INPUT Full-Scale Sense Voltage Common-Mode Input Range Common-Mode Rejection + – V– VSENSE = VIN IN 2.7 100 VIN+ = 2.7V to 40V, VSENSE = 50mV VIN+ = 2.7V to 60V, VSENSE = 50mV Offset Voltage(1) vs Temperature vs Power Supply, V+ OUTPUT Transconductance vs Temperature Nonlinearity Error Total Output Error Output Impedance Voltage Output Swing to Power Supply, V+ Swing to Common Mode, VCM INA168NA TYP MAX MIN 100 500 36 ✽ 100 ±1 198 200 10 ±0.01 ±0.5 1 || 5 202 ✽ ±0.1 ±2 Settling Time (0.1%) NOISE Output-Current Noise Density Total Output-Current Noise POWER SUPPLY Operating Range, V+ Quiescent Current ✽ ✽ 60 mV V dB dB mV µV/°C µV/V µV/V uA 120 ✽ ✽ ✽ 0.1 ✽ 10 ✽ ✽ ✽ ✽ ✽ ✽ ✽ ✽ ✽ ✽ µA/V nA/°C % % GΩ || pF V V R OUT = 5kΩ ROUT = 125kΩ 5V Step, ROUT = 5kΩ 5V Step, ROUT = 125kΩ 800 32 1.8 30 ✽ ✽ ✽ ✽ kHz kHz µs µs BW = 100kHz 9 3 ✽ ✽ pA/√Hz nA RMS 2.7 VSENSE = 0, IO = 0 25 –40 –55 –65 θJA 200 NOTE: (1) Defined as the amount of input voltage, VSENSE, to drive the output to zero. ® INA138, INA168 UNITS ✽ ✽ (V+) – 0.8 (V+) – 1.0 VCM – 0.5 VCM – 0.8 FREQUENCY RESPONSE Bandwidth MAX 10 2 VSENSE = 10mV – 150mV VSENSE = 100mV VSENSE = 10mV to 150mV VSENSE = 100mV TYP 120 ±0.2 1 0.1 TMIN to TMAX V– = 2.7V to 40V, VSENSE = 50mV V– = 2.7V to 60V, VSENSE = 50mV + , V– VIN IN Input Bias Current TEMPERATURE RANGE Specification, TMIN to TMAX Operating Storage Thermal Resistance MIN 2 36 45 ✽ 85 125 150 ✽ ✽ ✽ ✽ ✽ 60 ✽ V µA ✽ ✽ ✽ °C °C °C °C/W PIN CONFIGURATION TOP VIEW ELECTROSTATIC DISCHARGE SENSITIVITY SOT23 OUT 1 GND 2 + VIN 3 5 V+ 4 – VIN 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(1) Supply Voltage, V+ INA138 ............................................................................... –0.3V to 60V INA168 ............................................................................... –0.3V to 75V + – , VIN Analog Inputs, VIN INA138 Common Mode ............................................................... –0.3V to 60V + – ) ..................................................... –40V to 2V ) – (VIN Differential (VIN INA168 Common Mode ............................................................... –0.3V to 75V + – ) – (VIN ) ..................................................... –40V to 2V Differential (VIN 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. PACKAGE/ORDERING INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER INA138NA SOT23-5 Surface Mount 331 –40°C to +85°C B38 " " " " SOT23-5 Surface Mount 331 –40°C to +85°C A68 " " " " " INA168NA " SPECIFIED TEMPERATURE RANGE PACKAGE MARKING ORDERING NUMBER(1) TRANSPORT MEDIA INA138NA/250 INA138NA/3K Tape and Reel Tape and Reel INA168NA/250 INA168NA/3K Tape and Reel 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. 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 INA138, INA168 TYPICAL PERFORMANCE CURVES + = 12V, R = 125kΩ, unless otherwise noted. At TA = +25°C, V+ = 5V, VIN L COMMON-MODE REJECTION vs FREQUENCY GAIN vs FREQUENCY 40 120 Common-Mode Rejection (dB) RL = 500kΩ 30 RL = 50kΩ Gain (dB) 20 10 RL = 5kΩ 0 –10 CL = 10nF CL = 1nF CL = 100pF –20 G = 100 100 80 G = 10 60 G=1 40 20 0 100 10k 1k 100k 10M 1M 0.1 10 1 Frequency (Hz) 100 TOTAL OUTPUT ERROR vs VIN POWER-SUPPLY REJECTION vs FREQUENCY 5 + – V– ) VIN = (VIN IN –55°C 120 Total Output Error (%) Power-Supply Rejection (dB) 100k Frequency (Hz) 140 G = 100 100 G = 10 80 G=1 60 0 +150°C –5 +25°C –10 40 –15 20 1 100 1k Frequency (Hz) 10 0 100k 10k 25 50 75 100 125 150 200 VIN (mV) TOTAL OUTPUT ERROR vs POWER-SUPPLY VOLTAGE QUIESCENT CURRENT vs POWER-SUPPLY VOLTAGE 2 50 Output error is essentially independent of both V+ supply voltage and input common-mode voltage. 1 Quiescent Current (µA) Total Output Error (%) 10k 1k G=1 0 G = 10 G = 25 –1 –2 +150° 40 +125° 30 +25° –55° 20 Use INA168 with (V+) > 36V 10 0 10 0 20 30 40 50 60 70 0 Power-Supply Voltage (V) 20 30 40 50 Power-Supply Voltage (V) ® INA138, INA168 10 4 60 70 TYPICAL PERFORMANCE CURVES (Cont.) + = 12V, R = 125kΩ, unless otherwise noted. At TA = +25°C, V+ = 5V, VIN L STEP RESPONSE STEP RESPONSE 200mV G=1 G = 25 100mV 0V 1V/div 50mV/div 100mV G=1 G = 10 0mV 0V 10µs/div 500mV/div 10µs/div ® 5 INA138, INA168 OPERATION BASIC CONNECTION 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 voltage, VOUT, at the Out pin. The transfer function for the INA138 is: Figure 1 shows the basic connection of the INA138. The + and V – , should be connected as closely as input pins, VIN IN 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. + – V–) IO = gm (VIN IN (1) where gm = 200µA/V (2) 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 capacitors to reject power supply noise. Connect bypass capacitors close to the device pins. + – V – ), is In the circuit of Figure 1, the input voltage, (VIN IN 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) 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”). (3) The maximum differential input voltage for accurate measurements 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. SELECTING RS AND RL The value chosen for the shunt resistor, RS, depends on the application and is a compromise between small-signal accuracy and maximum permissible voltage loss in the measurement line. High values of RS provide better accuracy at VP Load Power Supply +2.7 to 36V(1) V+ power can be common or indepedent of load supply. Shunt RS + VIN IS – VIN 4 3 Load V+ RG1 5kΩ 2.7 ≤ (V+) ≤ 36V(1) RG2 5kΩ 5 Q1 VOLTAGE GAIN EXACT RL (Ω) NEAREST 1% RL (Ω) 1 5k 4.99k 2 10k 10k INA138 2 5 25k 24.9k 10 50k 49.9k 20 100k 100k 50 250k 249k 100 500k 499k + I0 RL VO – NOTE: (1) Maximum VP and V+ voltage is 60V with INA168. FIGURE 1. Basic Circuit Connections. ® INA138, INA168 OUT 1 6 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. output swing. The maximum output voltage compliance is limited by the lower of the two equations below: Vout (4) or 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. Vout max – – 0.5V = VIN (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 Performance 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. Some A/D converters have input impedances that will significantly 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. Alternatively, 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 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. IS 3 + – V–) = (V+) – 0.7V – (VIN IN max 4 3 4 f–3dB INA138 ZIN OPA340 RL 1 f–3dB = 2πRLCL INA138 VO Buffer of amp drives A/D converter without affecting gain. FIGURE 3. Output Filter. FIGURE 2. Buffering Output to Drive A/D Converter. 3 4 3 VR INA138 4 V+ REF200 100µA INA138 R1 V0 1 CL RL V0 1 R2 RL Gain Set by R1 R2 (VR)R2 R1+R2 Gain Set by RL Output Offset = (100µA)(RL) (independent of V+) Output Offset = a). Using resistor divider. b). Using current source. FIGURE 4. Offsetting the Output Voltage. ® 7 INA138, INA168 ±1A Charger 1Ω 4 3 +5V 4 3 5kΩ +5V 5kΩ 5 + 5 Load 48V INA168 INA168 2 1 2 1 Comparator IN4148 IN4148 SIGN 10KΩ 10KΩ 0 to 1V VO 100KΩ FIGURE 5. Bipolar Current Measurement. RS V+ 4 3 4 3 +5V +5V +5V 5 BUFOUT REFOUT BUFIN 5 Digital I/O INA138 BUF INA138 2 1 REF RL 25kΩ 2 1 MUX RL 25kΩ Clock Divider Oscillator A/D converter programmed for differential input. Depending on polarity of current, one INA138 provides an output voltage, the other's output is zero. FIGURE 6. Bipolar Current Measurement Using Differential Input of A/D Converter. ® INA138, INA168 8 12-Bit A/D PGIA Serial I/O ADS7870 Other INA168s Digital I/O on ADS7870 provides power to select the desired INA168. Diodes prevent output current of " on" INA168 from flowing into "off" INA168. INA168 V+ +5V –– REFOUT BUFIN Digital I/O REF BUFOUT BUF INA168 V+ –– MUX 12-Bit A/D PGIA IN4148 Clock Divider Oscillator RL Serial I/O ADS7870 FIGURE 7. Multiplexed Measurement Using Logic Signal for Power. ® 9 INA138, INA168 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI’s publication of information regarding any third party’s products or services does not constitute TI’s approval, warranty or endorsement thereof. Copyright 2000, Texas Instruments Incorporated