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| (R) INA138 INA168 For most current data sheet and other product information, visit www.burr-brown.com High-Side Measurement CURRENT SHUNT MONITOR FEATURES q COMPLETE UNIPOLAR HIGH-SIDE CURRENT MEASUREMENT CIRCUIT q WIDE SUPPLY AND COMMON-MODE RANGE q INA138: 2.7V to 36V q INA168: 2.7V to 60V q INDEPENDENT SUPPLY AND INPUT COMMON-MODE VOLTAGES q SINGLE RESISTOR GAIN SET q LOW QUIESCENT CURRENT (25A typ) q SOT23-5 PACKAGE DESCRIPTION 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 25A, 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. Both the INA138 and INA168 are available in SOT23-5 and are specified for the -40C to +85C industrial temperature range. APPLICATIONS q CURRENT SHUNT MEASUREMENT: Automotive, Telephone, Computers q PORTABLE & BATTERY-BACKUP SYSTEMS q BATTERY CHARGERS q POWER MANAGEMENT q CELL PHONES q PRECISION CURRENT SOURCE RS VIN+ Up To 60V 3 VIN+ 5k 4 VIN- IS Load 5k V+ 5 OUT GND 2 1 RL VO = ISRSRL/5k 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 (c)1999 Burr-Brown Corporation PDS-1576B Printed in U.S.A. August, 2000 SBOS122 SPECIFICATIONS At TA = -40C to +85C, VS = 5V, VIN+ = 12V, ROUT = 125k, unless otherwise noted. INA138NA PARAMETER INPUT Full-Scale Sense Voltage Common-Mode Input Range Common-Mode Rejection Offset Voltage(1) vs Temperature vs Power Supply, V+ Input Bias Current OUTPUT Transconductance vs Temperature Nonlinearity Error Total Output Error Output Impedance Voltage Output Swing to Power Supply, V+ Swing to Common Mode, VCM FREQUENCY RESPONSE Bandwidth Settling Time (0.1%) NOISE Output-Current Noise Density Total Output-Current Noise POWER SUPPLY Operating Range, V+ Quiescent Current TEMPERATURE RANGE Specification, TMIN to TMAX Operating Storage Thermal Resistance CONDITION + - VSENSE = VIN - VIN INA168NA MAX 500 36 MIN TYP V V 100 120 V V 0.1 V 202 0.1 2 V V V V V V V V V V V V V V 36 45 85 125 150 V V V V V V 60 V V V V MAX V 60 UNITS mV V dB dB mV V/C V/V V/V uA A/V nA/C % % G || pF V V kHz kHz s s pA/Hz nA RMS V A C C C C/W MIN TYP 100 VIN+ = 2.7V to 40V, VSENSE = 50mV VIN+ = 2.7V to 60V, VSENSE = 50mV TMIN to TMAX V- = 2.7V to 40V, VSENSE = 50mV V- = 2.7V to 60V, VSENSE = 50mV + - VIN , VIN VSENSE = 10mV - 150mV VSENSE = 100mV VSENSE = 10mV to 150mV VSENSE = 100mV 2.7 100 120 0.2 1 0.1 2 1 10 10 V 198 200 10 0.01 0.5 1 || 5 V V V (V+) - 0.8 (V+) - 1.0 VCM - 0.5 VCM - 0.8 R OUT = 5k ROUT = 125k 5V Step, ROUT = 5k 5V Step, ROUT = 125k 800 32 1.8 30 9 3 2.7 VSENSE = 0, IO = 0 -40 -55 -65 25 V V BW = 100kHz JA 200 NOTE: (1) Defined as the amount of input voltage, VSENSE, to drive the output to zero. (R) INA138, INA168 2 PIN CONFIGURATION TOP VIEW SOT23 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. OUT GND + VIN 1 2 3 5 V+ 4 - VIN ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage, V+ INA138 ............................................................................... -0.3V to 60V INA168 ............................................................................... -0.3V to 75V + - Analog Inputs, VIN , VIN INA138 Common Mode ............................................................... -0.3V to 60V + - Differential (VIN ) - (VIN ) ..................................................... -40V to 2V INA168 Common Mode ............................................................... -0.3V to 75V + - Differential (VIN ) - (VIN ) ..................................................... -40V to 2V Analog Output, Out .............................................................. -0.3V to 40V Operating Temperature .................................................. -55C to +125C Storage Temperature ..................................................... -55C to +125C Junction Temperature .................................................................... +150C Lead Temperature (soldering, 10s) ............................................... +300C 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 PACKAGE DRAWING NUMBER 331 SPECIFIED TEMPERATURE RANGE -40C to +85C PACKAGE MARKING B38 ORDERING NUMBER(1) INA138NA/250 INA138NA/3K INA168NA/250 INA168NA/3K TRANSPORT MEDIA Tape and Reel Tape and Reel Tape and Reel Tape and Reel PRODUCT INA138NA PACKAGE SOT23-5 Surface Mount " INA168NA " SOT23-5 Surface Mount " 331 " -40C to +85C " A68 " " " " " 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. (R) 3 INA138, INA168 TYPICAL PERFORMANCE CURVES + At TA = +25C, V+ = 5V, VIN = 12V, RL = 125k, unless otherwise noted. GAIN vs FREQUENCY 40 RL = 500k 30 RL = 50k 20 Gain (dB) 120 COMMON-MODE REJECTION vs FREQUENCY Common-Mode Rejection (dB) 100 80 G = 100 G = 10 60 G=1 40 20 0 10 0 -10 CL = 10nF -20 100 1k 10k 100k 1M 10M Frequency (Hz) CL = 1nF CL = 100pF RL = 5k 0.1 1 10 100 Frequency (Hz) 1k 10k 100k POWER-SUPPLY REJECTION vs FREQUENCY 140 TOTAL OUTPUT ERROR vs VIN 5 -55C + - VIN = (VIN - VIN) Power-Supply Rejection (dB) 120 G = 100 100 G = 10 80 G=1 60 40 20 1 10 100 1k Frequency (Hz) 10k 100k Total Output Error (%) 0 -5 +25C -10 +150C -15 0 25 50 75 100 125 150 200 VIN (mV) TOTAL OUTPUT ERROR vs POWER-SUPPLY VOLTAGE 2 Output error is essentially independent of both V+ supply voltage and input common-mode voltage. G=1 G = 10 -1 G = 25 50 QUIESCENT CURRENT vs POWER-SUPPLY VOLTAGE Quiescent Current (A) Total Output Error (%) 1 40 +150 +125 30 +25 20 -55 Use INA168 with (V+) > 36V 10 0 -2 0 10 20 30 40 50 60 70 Power-Supply Voltage (V) 0 0 10 20 30 40 50 60 70 Power-Supply Voltage (V) (R) INA138, INA168 4 TYPICAL PERFORMANCE CURVES + At TA = +25C, V+ = 5V, VIN = 12V, RL = 125k, unless otherwise noted. (Cont.) STEP RESPONSE STEP RESPONSE 200mV G=1 100mV 50mV/div 100mV G=1 0mV G = 10 0V 500mV/div G = 25 0V 1V/div 10s/div 10s/div (R) 5 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 voltage, VOUT, at the Out pin. The transfer function for the INA138 is: + - IO = gm (VIN - VIN ) 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 capacitors 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 accuracy and maximum permissible voltage loss in the measurement line. High values of RS provide better accuracy at (1) (2) where gm = 200A/V + - 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 200A/V. The complete transfer function for the current measurement amplifier in this application is: VOUT = (IS) (RS) (200A/V) (RL) (3) The maximum differential input voltage for accurate measurements is 0.5V, which produces a 100A 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. VP Load Power Supply +2.7 to 36V(1) Shunt RS + VIN - VIN IS V+ power can be common or indepedent of load supply. 2.7 (V+) 36V(1) 3 V+ RG1 5k 4 RG2 5k Load 5 Q1 VOLTAGE GAIN 1 2 5 10 20 50 100 EXACT RL () 5k 10k 25k 50k 100k 250k 500k NEAREST 1% RL () 4.99k 10k 24.9k 49.9k 100k 249k 499k INA138 2 OUT 1 I0 RL + VO - NOTE: (1) Maximum VP and V+ voltage is 60V with INA168. FIGURE 1. Basic Circuit Connections. (R) INA138, INA168 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. 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 500k 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 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 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 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. 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 4 3 INA138 OPA340 ZIN 4 f-3dB INA138 1 f-3dB = 2RLCL VO RL Buffer of amp drives A/D converter without affecting gain. RL CL FIGURE 2. Buffering Output to Drive A/D Converter. FIGURE 3. Output Filter. 3 4 VR 3 4 V+ INA138 R1 1 R2 V0 INA138 REF200 100A 1 RL V0 Output Offset = Gain Set by R1 R2 (VR)R2 R1+R2 Gain Set by RL Output Offset = (100A)(RL) (independent of V+) b). Using current source. a). Using resistor divider. FIGURE 4. Offsetting the Output Voltage. (R) 7 INA138, INA168 1A 1 Charger 3 4 4 3 +5V 5 48V 5k 5k 5 +5V Load + INA168 1 IN4148 2 INA168 2 IN4148 1 Comparator SIGN 10K 10K 0 to 1V VO 100K FIGURE 5. Bipolar Current Measurement. V+ RS 4 3 3 4 +5V +5V 5 5 +5V REFOUT BUFIN BUFOUT Digital I/O REF BUF INA138 1 2 INA138 2 1 MUX PGIA 12-Bit A/D RL 25k RL 25k Clock Divider Oscillator Serial I/O ADS7870 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. (R) INA138, INA168 8 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. V+ -- INA168 +5V REFOUT BUFIN BUFOUT Digital I/O INA168 V+ -- REF BUF MUX IN4148 PGIA 12-Bit A/D RL Clock Divider Oscillator Serial I/O ADS7870 FIGURE 7. Multiplexed Measurement Using Logic Signal for Power. (R) 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 (c) 2000, Texas Instruments Incorporated |
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