INA138NA/3K

Order Now Product Folder Support & Community Tools & Software Technical Documents Reference Design INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 INA1x8 High-Side Measurement Current Shunt Monitor 1 Features 3 Description • The INA138 and INA168 (INA1x8) are high-side, unipolar, current shunt monitors. Wide input commonmode voltage range, low quiescent current, and tiny SOT-23 packaging enable use in a variety of applications. 1 • • • • • • • • Complete Unipolar High-Side Current Measurement Circuit Wide Supply and Common-Mode Range INA138: 2.7 V to 36 V INA168: 2.7 V to 60 V Independent Supply and Input Common-Mode Voltages Single Resistor Gain Set Low Quiescent Current (25 µA Typical) Wide Temperature Range: –40°C to +125°C 5-Pin SOT-23 Package Input common-mode and power-supply voltages are independent and can range from 2.7 V to 36 V for the INA138 and 2.7 V to 60 V for the INA168. Quiescent current is only 25 µA, 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. 2 Applications • • • • • • Current Shunt Measurement: – Telephone, Computers Portable and Battery-Backup Systems Battery Chargers Power Management Cell Phones Precision Current Source Both the INA138 and INA168 are available in SOT235 and are specified for the –40°C to 125°C temperature range. Device Information(1) PART NUMBER INA138 INA168 PACKAGE SOT-23 (5) BODY SIZE (NOM) 2.90 mm × 1.60 mm (1) For all available packages, see the package option addendum at the end of the datasheet. Typical Application Circuit IS RS VIN+ Up To 60 V 3 4 VIN– VIN+ 5 kΩ Load 5 kΩ V+ 5 OUT GND 1 VO = ISRSRL / 5 kΩ 2 Copyright © 1999, Texas Instruments Incorporated 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 5 5 6 Absolute Maximum Ratings ...................................... ESD Ratings ............................................................ Recommended Operating Conditions....................... Thermal Information ................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description .............................................. 8 7.1 7.2 7.3 7.4 Overview ................................................................... Functional Block Diagram ......................................... Feature Description................................................... Device Functional Modes.......................................... 8 8 9 9 8 Application and Implementation ........................ 10 8.1 Application Information............................................ 10 8.2 Typical Applications ............................................... 11 9 Power Supply Recommendations...................... 18 10 Layout................................................................... 18 10.1 Layout Guidelines ................................................. 18 10.2 Layout Example .................................................... 18 11 Device and Documentation Support ................. 19 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Documentation Support ....................................... Related Links ........................................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 19 19 19 19 19 19 19 12 Mechanical, Packaging, and Orderable Information ........................................................... 20 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision D (December 2014) to Revision E Page • Added reference design link to navigation bar at the top of the front page ........................................................................... 1 • Changed body size from 18.00 mm × 18.00 mm to 2.90 mm × 1.60 mm in Device Information table.................................. 1 • Changed pin numbers in pin functions table to match pin configuration figure...................................................................... 3 • Changed Absolute Maximum Ratings table for clarity; no values were changed ................................................................. 4 • Changed Recommended Operating Conditions table; moved some content from Electrical Characteristics table, but no values changed ................................................................................................................................................................. 4 • Changed all values in Thermal Information table ................................................................................................................... 5 • Changed Electrical Characteristics table; reformatted for clarity; moved some content to Recommended Operating Conditions table, and deleted duplicate content..................................................................................................................... 5 • Changed common-mode rejection test conditions to better highlight each device in Electrical Characteristics table .......... 5 • Changed offset voltage vs temperature to offset voltage drift in Electrical Characteristics table........................................... 5 • Changed offset voltage vs power supply test conditions to better highlight each device in Electrical Characteristics table . 5 • Changed reference in text from Figure 10 to Figure 11 in last paragraph of Selecting the Shunt Resistor and RL section 12 Changes from Revision C (November 2005) to Revision D • 2 Page Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 5 Pin Configuration and Functions DBV Package 5-Pin SOT-23 Top View OUT 1 GND 2 VIN+ 3 5 V+ 4 VIN± Not to scale Pin Functions PIN NO. NAME I/O DESCRIPTION 1 OUT O Output current 2 GND — Ground 3 VIN+ I Positive input voltage 4 VIN– I Negative input voltage 5 V+ I Power supply voltage Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 3 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) INA138 Supply, V+ INA168 INA138 Voltage (1) Analog input, VIN+, VIN– INA168 75 –0.3 60 Sense voltage, VSENSE = (VIN+ – VIN–) –40 2 –0.3 75 Common mode (2) Sense voltage, VSENSE = (VIN+ – VIN–) 2 –0.3 40 –55 150 10 Junction, TJ mA 150 Storage, Tstg –65 UNIT V –40 Input current into any pin Temperature (2) 60 –0.3 Operating, TA (1) MAX Common mode (2) Analog output, OUT pin (2) Current MIN –0.3 °C 150 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. The input voltage at any pin may exceed the voltage shown if the current at that pin is limited to 10 mA. 6.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) ±1000 Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) ±500 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT INA138 V+ Supply voltage VSENSE Full-scale sense voltage (VIN+ – VIN–) 2.7 5 36 V 100 500 mV Common-mode voltage 2.7 12 36 V Operating temperature –40 25 125 °C V+ Supply voltage 2.7 VSENSE Full-scale sense voltage (VIN+ – VIN–) TA INA168 TA 4 5 60 V 100 500 mV Common-mode voltage 2.7 12 60 V Operating temperature –40 25 125 °C Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 6.4 Thermal Information INA1x8 THERMAL METRIC (1) DBV UNIT 5 PINS RθJA Junction-to-ambient thermal resistance 168.3 °C/W RθJC(top) Junction-to-case (top) thermal resistance 73.8 °C/W RθJB Junction-to-board thermal resistance 28.1 °C/W ψJT Junction-to-top characterization parameter 2.5 °C/W ψJB Junction-to-board characterization parameter 27.6 °C/W (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. 6.5 Electrical Characteristics all other characteristics at TA = +25°C, VS = 5 V, VIN+ = 12 V, and ROUT = 125 kΩ (unless otherwise noted) PARAMETER TEST CONDITIONS INA1x8 MIN TYP INA138, VIN+ = 2.7 V to 36 V 100 120 INA168, VIN+ = 2.7 V to 60 V 100 120 MAX UNIT INPUT Common-mode rejection Offset voltage (1) Offset voltage drift (1) Offset voltage vs power supply, V+ Input bias current VSENSE = 50 mV TA = 25°C ±0.2 TA = –40°C to +125°C ±1 mV ±2 TA = –40°C to +125°C VSENSE = 50 mV dB 1 µV/°C INA138, V+ = 2.7 V to 36 V 0.1 10 INA168, V+ = 2.7 V to 60 V 0.1 10 TA = 25°C µV/V 2 TA = –40°C to +125°C, INA138 µA 10 OUTPUT Transconductance VSENSE = 10 mV to 150 mV, TA = 25°C 198 VSENSE = 100 mV, TA = –40°C to +125°C 196 Transconductance drift TA = –40°C to +125°C Nonlinearity error VSENSE = 10 mV to 150 mV Total output error VSENSE = 100 mV 202 204 10 µA/V µA/V nA/°C ±0.01% ±0.1% TA = 25°C ±0.5% ±2% TA = –40°C to +125°C ±2.5% Output impedance Voltage output swing 200 1 || 5 GΩ || pF To power supply voltage, V+ (V+) – 0.8 (V+) – 1.0 V To common-mode voltage, VCM VCM – 0.5 VCM – 0.8 V FREQUENCY RESPONSE Bandwidth Settling time ROUT = 5 kΩ 800 kHz 32 kHz 5-V step, ROUT = 5 kΩ 1.8 µs 5-V step, ROUT = 125 kΩ 30 µs 9 pA/√Hz 3 nA RMS ROUT = 125 kΩ To 0.1% NOISE Output-current noise density Total output-current noise BW = 100 kHz POWER SUPPLY Quiescent current (1) VSENSE = 0 V, IO = 0 mA TA = 25°C TA = –40°C to +125°C 25 45 µA 60 µA Defined as the amount of input voltage, VSENSE, to drive the output to zero. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 5 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 6.6 Typical Characteristics At TA = +25°C, V+ = 5 V, VIN+ = 12 V, and RL = 125 kΩ, unless otherwise noted. 40 120 Common-Mode Rejection (dB) RL = 500kΩ 30 RL = 50kΩ Gain (dB) 20 10 RL = 5kΩ 0 –10 CL = 10nF –20 100 1k CL = 1nF 10k CL = 100pF 100k 1M G = 100 100 80 G = 10 60 G=1 40 20 0 10M 0.1 Frequency (Hz) 1 10 100 1k 10k 100k Frequency (Hz) Figure 1. Gain vs Frequency Figure 2. Common-Mode Rejection vs Frequency 140 5 VIN = (VIN+ – VIN–) G = 100 100 G = 10 80 G=1 60 Total Output Error (%) Power-Supply Rejection (dB) –55°C 120 0 +150°C –5 +25°C –10 40 –15 20 1 10 100 1k Frequency (Hz) 10k 0 100k 25 100 125 150 200 Figure 4. Total Output Error vs VIN 2 50 Output error is essentially independent of both V+ supply voltage and input common-mode voltage. 1 G=1 0 G = 10 G = 25 –1 +150° 40 Quiescent Current (µA) Total Output Error (%) 75 VIN (mV) Figure 3. Power-Supply Rejection vs Frequency –2 +125° 30 +25° –55° 20 Use INA168 with (V+) > 36V 10 0 0 10 20 30 40 50 60 70 0 10 Power-Supply Voltage (V) 20 30 40 50 60 70 Power-Supply Voltage (V) Figure 5. Total Output Error vs Power-Supply Voltage 6 50 Figure 6. Quiescent Current vs Power-Supply Voltage Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 Typical Characteristics (continued) At TA = +25°C, V+ = 5 V, VIN+ = 12 V, and RL = 125 kΩ, unless otherwise noted. m m Figure 8. Step Response Figure 7. Step Response Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 7 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 7 Detailed Description 7.1 Overview The INA138 and INA168 devices (INA1x8) are comprised of a high voltage, precision operational amplifier, precision thin film resistors trimmed in production to an absolute tolerance and a low noise output transistor. The INA1x8 devices can be powered from a single power supply and their input voltages can exceed the power supply voltage. The INA1x8 devices are ideal for measuring small differential voltages, such as those generated across a shunt resistor, in the presence of large common-mode voltages. Refer to Functional Block Diagram which illustrates the functional components within both INA1x8 devices. 7.2 Functional Block Diagram VIN+ VIN– V+ OUT GND 8 Copyright © 2014, Texas Instruments Incorporated Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 7.3 Feature Description 7.3.1 Output Voltage Range The output of the INA1x8 device is a current that 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 (Vout max) compliance is limited by either Equation 1 or Equation 2, whichever is lower: Vout max = (V+) – 0.7 V – (VIN+ – VIN–) (1) Vout max = VIN– – 0.5 V (2) or 7.3.2 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 Characteristics). 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 Characteristics. If bandwidth limiting (filtering) is desired, a capacitor can be added to the output (see Figure 12). This will not cause instability. 7.4 Device Functional Modes For proper operation the INA1x8 devices must operate within their specified limits. Operating either device outside of their specified power supply voltage range or their specified common-mode range will result in unexpected behavior and is not recommended. Additionally operating the output beyond their specified limits with respect to power supply voltage and input common-mode voltage will also produce unexpected results. Refer to Electrical Characteristics for the device specifications. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 9 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information 8.1.1 Operation Figure 9 illustrates the basic circuit diagram for both the INA138 and INA168 devices. Load current IS is drawn from supply VS through shunt resistor RS. The voltage drop in 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 device is: IO = gm(VIN+ – VIN–) (3) where gm = 200 µA/V. In the circuit of Figure 9, 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 device is 200 µA/V. The complete transfer function for the current measurement amplifier in this application is: VOUT = (IS) (RS) (200 µA/V) (RL) (4) The maximum differential input voltage for accurate measurements is 0.5 V, which produces a 100-µA output current. A differential input voltage of up to 2 V 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 V to 36 V(1) Shunt RS VIN– VIN+ 3 V+ power can be common or V+ independent of load supply. 4 RG1 5 kΩ 2.7 V ≤ (V+) ≤ 36 V(1) IS Load RG2 5 kΩ 5 Q1 (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 INA138 2 OUT 1 + I0 RL VO – Copyright © 1999, Texas Instruments Incorporated Maximum VP and V+ voltage is 60 V with INA168. Figure 9. Basic Circuit Connections 10 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 8.2 Typical Applications The INA1x8 devices are designed for current shunt measurement circuits, as shown in Figure 9, but basic device 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 illustrated in Figure 10 through Figure 18. 8.2.1 Buffering Output to Drive an ADC IS VIN+ VIN- OPA340 + INA138 or INA168 RS ADC RL Buffer amplifier drives ADC without affecting gain C Figure 10. Buffering Output to Drive an ADC 8.2.1.1 Design Requirements Digitize the output of the INA1x8 devices using a 1-MSPS analog-to-digital converter (ADC). 8.2.1.2 Detailed Design Procedure 8.2.1.2.1 Selecting the Shunt Resistor and RL In Figure 9 the value chosen for the shunt resistor depends on the application and is a compromise between small-signal accuracy and maximum permissible voltage loss in the measurement line. High values of shunt resistor provide better accuracy at lower currents by minimizing the effects of offset, while low values of shunt resistor minimize voltage loss in the supply line. For most applications, best performance is attained with a shunt resistor value that provides a full-scale shunt voltage range of 50 mV to 100 mV. Maximum input voltage for accurate measurements is 500 mV. The load resistor, RL, is chosen to provide the desired full-scale output voltage. The output impedance of the INA1x8 OUT terminal is very high which permits using values of RL up to 500 kΩ 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 analog-to-digital converters (ADCs) have input impedances that significantly affect measurement gain. The input impedance of the ADC 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 ADC input. The INA1x8 are current output devices, and as such have an inherently large output impedance. The output currents from the amplifier are converted to an output voltage via the load resistor, RL, connected from the amplifier output to ground. The ratio of the load resistor value to that of the internal resistor value determines the voltage gain of the system. In many applications digitizing the output of the INA1x8 device is required, and can be accomplished by connecting the output of the amplifier to an ADC. It is very common for an ADC to have a dynamic input impedance. If the INA1x8 output is connected directly to an ADC input, the input impedance of the ADC is effectively connected in parallel with the gain setting resistor RL. This parallel impedance combination will affect the gain of the system and the impact on the gain is difficult to estimate accurately. A simple solution that eliminates the paralleling of impedances, simplifying the gain of the circuit is to place a buffer amplifier, such as the OPA340, between the output of the INA138 or INA168 device and the input to the ADC. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 11 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com Typical Applications (continued) Figure 10 illustrates this concept. Notice that a low pass filter is placed between the OPA340 output and the input to the ADC. The filter capacitor is required to provide any instantaneous demand for current required by the input stage of the ADC. The filter resistor is required to isolate the OPA340 output from the filter capacitor to maintain circuit stability. The values for the filter components will vary according to the operational amplifier used for the buffer and the particular ADC selected. More information can be found regarding the design of the low pass filter in the TI Precision Design , 16 bit 1MSPS Data Acquisition Reference Design for Single-Ended Multiplexed Applications (TIPD173). Figure 11 shows the expected results when driving an analog-to-digital converter at 1MSPS with and without buffering the INA1x8 output. Without the buffer, the high impedance of the INA1x8 reacts with the input capacitance and sample and hold (S/H) capacitance of the ADC, and does not allow the S/H to reach the correct final value before it is reset and the next conversion starts. Adding the buffer amplifier significantly reduces the output impedance driving the S/H and allows for higher conversion rates than can be achieved without adding the buffer. 8.2.1.3 Application Curve Input to ADC (0.25 V/div) with buffer without Buffer Time Figure 11. Driving an ADC With and Without a Buffer 12 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 Typical Applications (continued) 8.2.2 Output Filter 3 4 f–3dB 1 f–3dB = 2 πR L C L INA138 VO RL CL Figure 12. Output Filter 8.2.2.1 Design Requirements Filter the output of the INA1x8 devices. 8.2.2.2 Detailed Design Procedure A low-pass filter can be formed at the output of the INA1x8 devices simply by placing a capacitor of the desired value in parallel with the load resistor. First determine the value of the load resistor needed to achieve the desired gain. Refer to the table in Figure 9. Next, determine the capacitor value that will result in the desired cutoff frequency according to the equation shown in Figure 12. Figure 13 illustrates various combinations of gain settings (determined by RL) and filter capacitors. 8.2.2.3 Application Curve 40 RL = 500kΩ 30 RL = 50kΩ Gain (dB) 20 10 0 RL = 5kΩ –10 CL = 10nF –20 100 1k 10k CL = 1nF 100k CL = 100pF 1M 10M Frequency (Hz) Figure 13. Gain vs Frequency Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 13 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com Typical Applications (continued) 8.2.3 Offsetting the Output Voltage For many applications using only a single power supply it may be required to level shift the output voltage away from ground when there is no load current flowing in the shunt resistor. Level shifting the output of the INA1x8 devices is easily accomplished by one of two simple methods shown in Figure 14. The method on the left hand side of Figure 14 illustrates a simple voltage divider method. This method is useful for applications that require the output of the INA1x8 devices to remain centered with respect to the power supply at zero load current through the shunt resistor. Using this method the gain is determine by the parallel combination of R1 and R2 while the output offset is determined by the voltage divider ratio R1 and R2. For applications that may require a fixed value of output offset, independent of the power supply voltage, the current source method shown on the right-hand side of Figure 14 is recommended. With this method a REF200 constant current source is used to generate a constant output offset. Using his method the gain is determined by RL and the offset is determined by the product of the value of the current source and RL. 3 VR 4 3 R1 INA138 V+ 4 REF200 100 µA INA138 VO VO 1 1 R2 Gain Set by R1 || R2 Output Offset = RL Gain Set by RL Output Offset = (100 µA)(RL) (independent of V+) (VR)R2 R1 + R2 a) Using resistor divider. b) Using current source. Figure 14. Offsetting the Output Voltage 14 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 Typical Applications (continued) 8.2.4 Bipolar Current Measurement The INA1x8 devices can be configured as shown in Figure 15 in applications where measuring current bidirectionally is required. Two INA devices are required connecting their inputs across the shunt resistor as shown in Figure 15. A comparator, such as the TLV3201, is used to detect the polarity of the load current. The magnitude of the load current is monitored across the resistor connected between ground and the connection labeled Output. In this example the 100-kΩ resistor results in a gain of 20 V/V. The 10-kΩ resistors connected in series with the INA1x8 output current are used to develop a voltage across the comparator inputs. Two diodes are required to prevent current flow into the INA1x8 output, as only one device at a time is providing current to the Output connection of the circuit. The circuit functionality is illustrated in Figure 16. ±1 A Load Curent RSH 100 m VIN+ VIN± VIN± VIN+ Bus Voltage Load Current 5k 5k 5k V+ + INA138 or INA168 +5 V V+ + +5 V 5k OUT OUT GND GND 1N4148 INA138 or INA168 1N4148 + Sign TLV3201 10 k 10 k Output 100 k Figure 15. Bipolar Current Measurement Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 15 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com Typical Applications (continued) Voltage Load Current Output Sign Time Figure 16. Bipolar Current Measurements Results (arbitrary scale) 8.2.5 Bipolar Current Measurement Using Differential Input of ADC The INA1x8 devices can be used with an ADC such as the ADS7870 programmed for differential mode operation. Figure 17 illustrates this configuration. In this configuration the use of two INAs allows for bidirectional current measurement. Depending upon the polarity of the current, one of the INAs provides an output voltage, while the other output is zero. In this way the ADC reads the polarity of current directly, without the need for additional circuitry. RS V+ 4 3 4 3 +5V +5V +5V 5 REFOUT BUFIN BUFOUT 5 Digital I/O INA138 2 1 RL 25kΩ REF BUF INA138 2 1 MUX PGIA 12-Bit A/D Converter RL 25kΩ A/D converter programmed for differential input. Depending on polarity of current, one INA138 provides an output voltage, the output of the other is zero. Clock Divider Oscillator ADS7870 Serial I/O Figure 17. Bipolar Current Measurement Using Differential Input of ADC 16 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 Typical Applications (continued) 8.2.6 Multiplexed Measurement Using Logic Signal for Power Multiple loads can be measured as illustrated in Figure 18. In this configuration each INA1x8 device is powered by the digital I/O from the ADS7870. Multiplexing is achieved by switching on or off each the desired I/O. Other INA168s Digital I/O on the ADS7870 provides power to select the desired INA168. Diodes prevent output current of the on INA168 from flowing into the off INA168. INA168 V+ +5V –– REFOUT BUFIN Digital I/O REF BUFOUT BUF INA168 V+ –– MUX 12-Bit A/D Converter PGIA IN4148 RL Clock Divider Oscillator Serial I/O ADS7870 Figure 18. Multiplexed Measurement Using Logic Signal for Power Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 17 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 9 Power Supply Recommendations The input circuitry of the INA138 can accurately measure beyond its power-supply voltage, V+. For example, the V+ power supply can be 5 V, whereas the load power supply voltage is up to 36 V (or 60 V with the INA168). The output voltage range of the OUT terminal, however, is limited by the lesser of the two voltages (see Output Voltage Range). A 0.1-µF capacitor is recommenced to be placed near the power supply pin on the INA138 or INA168. Additional capacitance may be required for applications with noisy power supply voltages. 10 Layout 10.1 Layout Guidelines Figure 19 shows the basic connection of the INA138 device. 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 decoupling capacitors to reject power-supply noise. Connect bypass capacitors close to the device pins. 10.2 Layout Example VIA to Ground Plane INA138 INA168 Output OUT Supply Voltage V+ 0.1 µF GND RL To Bus Voltage VIN+ VIN- PCB pad To Load PCB pad RSHUNT Figure 19. Typical Layout Example 18 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 INA138, INA168 www.ti.com SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 11 Device and Documentation Support 11.1 Documentation Support 11.1.1 Related Documentation For related documentation see the following: • 16 bit 1MSPS Data Acquisition Reference Design for Single-Ended Multiplexed Applications • ADS7870 12-Bit ADC, MUX, PGA and Internal Reference Data Acquisition System • TLV3201, TLV3202 40-ns, microPOWER, Push-Pull Output Comparators • REF200 Dual Current Source/Current Sink 11.2 Related Links Table 1 lists quick access links. Categories include technical documents, support and community resources, tools and software, and quick access to sample or buy. Table 1. Related Links PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL DOCUMENTS TOOLS & SOFTWARE SUPPORT & COMMUNITY INA138 Click here Click here Click here Click here Click here INA168 Click here Click here Click here Click here Click here 11.3 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 11.4 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.5 Trademarks E2E is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 11.6 Electrostatic Discharge Caution This integrated circuit can be damaged by ESD. Texas Instruments 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. 11.7 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 19 INA138, INA168 SBOS122E – DECEMBER 1999 – REVISED DECEMBER 2017 www.ti.com 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 20 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: INA138 INA168 PACKAGE OPTION ADDENDUM www.ti.com 26-Aug-2017 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) INA138NA/250 ACTIVE SOT-23 DBV 5 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 B38 INA138NA/3KG4 ACTIVE SOT-23 DBV 5 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 125 B38 INA168NA/250 ACTIVE SOT-23 DBV 5 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR INA168NA/3K ACTIVE SOT-23 DBV 5 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR A68 -40 to 125 A68 (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