Refer to the PDF data sheet for device specific package drawings
The INA139-Q1 and INA169-Q1 (INA1x9-Q1) are high-side, unidirectional, current shunt monitors. Wide input common-mode voltage range, high-speed, low quiescent current, and TSSOP-8 packaging enable use in a variety of applications.
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 INA139-Q1 and INA169-Q1 are available in a TSSOP-8 package, and are specified for the –40°C to +125°C temperature range.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
INA139-Q1 | TSSOP (8) | 4.40 mm × 3.00 mm |
INA169-Q1 |
Changes from E Revision (May 2011) to F Revision
MIN | MAX | UNIT | ||||
---|---|---|---|---|---|---|
Voltage | Supply, V+ | INA139-Q1 | –0.3 | 60 | V | |
INA169-Q1 | –0.3 | 75 | V | |||
Analog inputs, VIN+, VIN– | Common mode | INA139-Q1 | –0.3 | 60 | V | |
INA169-Q1 | –0.3 | 75 | V | |||
Differential, (VIN+) – (VIN–) | –40 | 2 | V | |||
Analog output, OUT | –0.3 | 40 | V | |||
Temperature | Operating, TA | –55 | 125 | °C | ||
Junction, TJ | 150 | °C | ||||
Storage, Tstg | –65 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per AEC Q100-002(1) | ±2000 | V |
Charged-device model (CDM), per AEC Q100-011 | ±1000 |
MIN | NOM | MAX | UNIT | ||
---|---|---|---|---|---|
Supply voltage, V+ | INA139-Q1 | 2.7 | 5 | 40 | V |
INA169-Q1 | 2.7 | 5 | 60 | V | |
Common mode voltage | INA139-Q1 | 2.7 | 12 | 40 | V |
INA169-Q1 | 2.7 | 12 | 60 | V | |
Operating temperature, TA | –40 | 125 | °C |
THERMAL METRIC(1) | INA1x9-Q1 | UNIT | |
---|---|---|---|
PW (TSSOP) | |||
8 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 179.1 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 62.6 | °C/W |
RθJB | Junction-to-board thermal resistance | 107.7 | °C/W |
ψJT | Junction-to-top characterization parameter | 7 | °C/W |
ψJB | Junction-to-board characterization parameter | 106 | °C/W |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | N/A | °C/W |
PARAMETER | TEST CONDITIONS | INA139-Q1 | INA169-Q1 | UNIT | ||||||
---|---|---|---|---|---|---|---|---|---|---|
MIN | TYP | MAX | MIN | TYP | MAX | |||||
INPUT | ||||||||||
Full-scale sense voltage | VSENSE = VIN+ − VIN− | 100 | 500 | 100 | 500 | mV | ||||
Common-mode rejection | VIN+ = 2.7 V to 40 V, VSENSE = 50 mV | 100 | 115 | dB | ||||||
VIN+ = 2.7 V to 60 V, VSENSE = 50 mV | 100 | 120 | ||||||||
Offset voltage(1) RTI | ±0.2 | ±2 | ±0.2 | ±2 | mV | |||||
Offset voltage vs temperature | 1 | 1 | μV/°C | |||||||
Offset voltage vs power supply (V+) | VIN+ = 2.7 V to 40 V, VSENSE = 50 mV | 0.5 | 10 | μV/V | ||||||
VIN+ = 2.7 V to 60 V, VSENSE = 50 mV | 0.1 | 10 | ||||||||
Input bias current | 10 | 10 | μA | |||||||
OUTPUT | ||||||||||
Transconductance | VSENSE = 10 mV to 150 mV | 980 | 1000 | 1020 | 980 | 1000 | 1020 | μA/V | ||
Transconductance versus temperature | VSENSE = 100 mV | 10 | 10 | nA/°C | ||||||
Nonlinearity error | VSENSE = 10 mV to 150 mV | ±0.01% | ±0.2% | ±0.01% | ±0.2% | |||||
Total output error | VSENSE = 100 mV | ±0.5% | ±2% | ±0.5% | ±2% | |||||
Output impedance | 1 || 5 | 1 || 5 | GΩ || pF | |||||||
Voltage output swing to power supply (V+) | (V+) − 0.9 | (V+) − 1.2 | (V+) − 0.9 | (V+) − 1.2 | V | |||||
Voltage output swing to common mode, VCM | VCM − 0.6 | VCM − 1 | VCM − 0.6 | VCM − 1 | V | |||||
FREQUENCY RESPONSE | ||||||||||
Bandwidth | RL = 10 kΩ | 440 | 440 | kHz | ||||||
RL = 20 kΩ | 220 | 220 | ||||||||
Settling time (0 1%) | 5 V step, RL = 10 kΩ | 2.5 | 2.5 | μs | ||||||
5 V step, RL = 20 kΩ | 5 | 5 | ||||||||
NOISE | ||||||||||
Output-current noise density | 20 | 20 | pA/√Hz | |||||||
Total output-current noise | BW = 100 kHz | 7 | 7 | nA RMS | ||||||
POWER SUPPLY | ||||||||||
Quiescent current | VSENSE = 0 V, IO = 0 mA | 60 | 125 | 60 | 125 | μA |
The INA139-Q1 and INA169-Q1 devices (INA1x9-Q1) 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 INA1x9-Q1 are powered from a single power supply, and the input voltages can exceed the power-supply voltage. The INA1x9-Q1 are ideal for measuring small differential voltages, such as those generated across a shunt resistor in the presence of large, common-mode voltages. The Functional Block Diagram illustrates the functional components within both the INA139-Q1 and INA169-Q1 devices.
The output of the INA1x9-Q1 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 and Equation 2, whichever is lower:
or
Measurement bandwidth is affected by the value of the load resistor, RL. High gain produced by high values of RL yields a narrower measurement bandwidth (see the Typical Characteristics section). For the 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, add a capacitor can be added to the output (see Figure 12). This capacitor does not cause instability.
For proper operation, the INA1x9-Q1 must operate within the specified limits. Operating either device outside of their specified power supply voltage range, or their specified common-mode range, results in unexpected behavior, and is not recommended. Additionally, operating the output beyond the specified limits, with respect to power supply voltage and input common-mode voltage, also produces unexpected results. See the Electrical Characteristics for the device specifications.
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.
Figure 9 illustrates the basic circuit diagram for both the INA139-Q1 and INA169-Q1. Load current IS is drawn from supply VP through shunt resistor RS. The voltage drop in shunt resistor RS 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, IO, to a voltage, VOUT, at the OUT pin. The transfer function for the INA1x9-Q1 is given by Equation 3:
where
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 INA1x9-Q1 is 1000 μA/V. The complete transfer function for the current measurement amplifier in this application is given by Equation 4:
The maximum differential input voltage for accurate measurements is 0.5 V, producing a 500-μA output current. A differential input voltage of up to 2 V does not cause damage. Differential measurements (VIN+ and VIN− pins) must be unipolar, with a more-positive voltage applied to the VIN+ pin. If a more-negative voltage is applied to VIN+ pin, IO goes to zero, but no damage occurs.
VOLTAGE GAIN | EXACT RL (kΩ) | NEAREST 1% RL (kΩ) |
---|---|---|
1 | 1 | 1 |
2 | 2 | 2 |
5 | 5 | 4.99 |
10 | 10 | 10 |
20 | 20 | 20 |
50 | 50 | 49 |
100 | 100 | 100 |
The INA1x9-Q1 are designed for current-shunt measurement circuits, as shown in Figure 9, but the basic function is useful in a wide range of circuitry. With a little creativity, many unforeseen uses are found in measurement and level shifting circuits. A few ideas are illustrated in the following subsections.
Digitize the output of the INA139-Q1 or INA169-Q1 devices using a 1-MSPS analog-to-digital converter (ADC).
For this design example, use the input parameters shown in Table 2.
DESIGN PARAMETER | EXAMPLE VALUE |
---|---|
Supply voltage, V+ | 5 V |
Common-mode voltage, VCM | INA139-Q1: 2.7 V to 40 V |
INA169-Q1: 2.7 V to 60 V | |
Full-scale shunt voltage, VSENSE | 50 mV to 100 mV |
Load resistor, RL | 1 kΩ to 100 kΩ |
In Figure 10, 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 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 range of 50 mV to 100 mV. Maximum input voltage for accurate measurements is 500 mV.
Choose an RL that provides the desired full-scale output voltage. The output impedance of the INA1x9-Q1 OUT pin is very high, permitting the use of RL values up to 100 kΩ with excellent accuracy. The input impedance of any additional circuitry at the output must be much higher than the value of RL to avoid degrading accuracy.
Some ADCs have input impedances that 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 ADC input, as shown in Figure 10. The INA1x9-Q1 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 using 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 INA1x9-Q1 is required. Digitizing is 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 INA1x9-Q1 output is connected directly to an ADC input, the input impedance of the ADC is effectively connected in parallel with gain setting resistor RL. This parallel impedance combination affects 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, and simplifies the gain of the circuit is to place a buffer amplifier, such as the OPA340, between the output of the INA1x9-Q1 and the input to the ADC.
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 in order to maintain circuit stability. The values for the filter components vary according to the operational amplifier used for the buffer and the particular ADC selected. More information regarding the design of the low-pass filter is found 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 ADC at 1 MSPS with and without buffering the INA1x9-Q1 output. Without the buffer, the high impedance of the INA1x9-Q1 reacts with the input capacitance and sample-and-hold capacitance of the ADC, and does not allow the sampled value to reach the correct final value before the ADC is reset, and the next conversion starts. Adding the buffer amplifier significantly reduces the output impedance driving the sample-and-hold circuitry, and allows for higher conversion rates.
Filter the output of the INA139-Q1 or INA169-Q1 devices.
For this design example, use the input parameters shown in Table 3.
DESIGN PARAMETER | EXAMPLE VALUE |
---|---|
Supply voltage, V+ | INA139-Q1: 0 V to 40 V |
INA169-Q1: 0 V to 60 V | |
Common-mode voltage, VCM | INA139-Q1: 0 V to 40 V |
INA169-Q1: 0 V to 60 V | |
Full-scale shunt voltage, VSENSE | 50 mV to 100 mV |
Load resistor, RL | 1 kΩ to 100 kΩ |
A low-pass filter can be formed at the output of the INA1x9-Q1 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 by using Table 1. Next, determine the capacitor value that results in the desired cutoff frequency according to the equation shown in Figure 12. Figure 13 shows the frequency response with different RL values and a fixed filter capacitor.
For many applications using only a single power supply, the output voltage may have to be level shifted away from ground when there is no load current flowing in the shunt resistor. Level shifting the output of the INA1x9-Q1 is easily accomplished by one of two simple methods shown in Figure 14. Method (a) 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 INA1x9-Q1 to remain centered with respect to the power supply at a zero load current through the shunt resistor. Using this method, the gain is determined by the parallel combination of R1 and R2, while the output offset is determined by the voltage divider ratio of R1 and R2, as shown in Figure 14(a). For applications that require a fixed value of output offset independent of the power supply voltage, use current-source method (b), shown on the right-hand side of Figure 14. 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.
Configure the INA1x9-Q1 as shown in Figure 15 for applications where bidirectional current measurement is required. Two INA1x9-Q1 devices are required; connect the 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 20-kΩ resistor results in a gain of 20 V/V. The 10-kΩ resistors connected in series with the INA1x9-Q1 output current are used to develop a voltage across the comparator inputs. Two diodes are required to prevent current flow into the INA1x9-Q1 output because only one device at a time provides current to the Output connection of the circuit. The circuit functionality is illustrated in Figure 16.
Use the INA1x9-Q1 with an ADC, such as the ADS7870, programmed for differential-mode operation; Figure 17 illustrates this configuration. In this configuration, the use of two INA138-Q1s or INA168-Q1s allows for bidirectional current measurement. Depending on the polarity of the current, one of the INA devices provides an output voltage, while the other INA device output is zero. In this way, the ADC reads the polarity of current directly, without the need for additional circuitry.
Measure multiple loads as shown in Figure 18. In this configuration, each INA1x9-Q1 device is powered by the digital I/O from the ADS7870. Multiplexing is achieved by switching on or off each desired I/O.