The INA138 and INA168 (INA1x8) 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 2.7 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.
Both the INA138 and INA168 are available in SOT23-5 and are specified for the –40°C to 125°C temperature range.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
INA138 | SOT-23 (5) | 2.90 mm × 1.60 mm |
INA168 |
Changes from D Revision (December 2014) to E Revision
Changes from C Revision (November 2005) to D Revision
MIN | MAX | UNIT | ||||
---|---|---|---|---|---|---|
Voltage | Supply, V+ | INA138 | –0.3 | 60 | V | |
INA168 | –0.3 | 75 | ||||
Analog input, VIN+, VIN– | INA138 | Common mode(2) | –0.3 | 60 | ||
Sense voltage, VSENSE = (VIN+ – VIN–) | –40 | 2 | ||||
INA168 | Common mode(2) | –0.3 | 75 | |||
Sense voltage, VSENSE = (VIN+ – VIN–) | –40 | 2 | ||||
Analog output, OUT pin(2) | –0.3 | 40 | ||||
Current | Input current into any pin | 10 | mA | |||
Temperature | Operating, TA | –55 | 150 | °C | ||
Junction, TJ | 150 | |||||
Storage, Tstg | –65 | 150 |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±1000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±500 |
THERMAL METRIC(1) | INA1x8 | UNIT | |
---|---|---|---|
DBV | |||
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 |
PARAMETER | TEST CONDITIONS | INA1x8 | UNIT | ||||
---|---|---|---|---|---|---|---|
MIN | TYP | MAX | |||||
INPUT | |||||||
Common-mode rejection | VSENSE = 50 mV | INA138, VIN+ = 2.7 V to 36 V | 100 | 120 | dB | ||
INA168, VIN+ = 2.7 V to 60 V | 100 | 120 | |||||
Offset voltage(1) | TA = 25°C | ±0.2 | ±1 | mV | |||
TA = –40°C to +125°C | ±2 | ||||||
Offset voltage drift(1) | TA = –40°C to +125°C | 1 | µV/°C | ||||
Offset voltage vs power supply, V+ | VSENSE = 50 mV | INA138, V+ = 2.7 V to 36 V | 0.1 | 10 | µV/V | ||
INA168, V+ = 2.7 V to 60 V | 0.1 | 10 | |||||
Input bias current | TA = 25°C | 2 | µA | ||||
TA = –40°C to +125°C, INA138 | 10 | ||||||
OUTPUT | |||||||
Transconductance | VSENSE = 10 mV to 150 mV, TA = 25°C | 198 | 200 | 202 | µA/V | ||
VSENSE = 100 mV, TA = –40°C to +125°C | 196 | 204 | µA/V | ||||
Transconductance drift | TA = –40°C to +125°C | 10 | nA/°C | ||||
Nonlinearity error | VSENSE = 10 mV to 150 mV | ±0.01% | ±0.1% | ||||
Total output error | VSENSE = 100 mV | TA = 25°C | ±0.5% | ±2% | |||
TA = –40°C to +125°C | ±2.5% | ||||||
Output impedance | 1 || 5 | GΩ || pF | |||||
Voltage output swing | 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 | ROUT = 5 kΩ | 800 | kHz | ||||
ROUT = 125 kΩ | 32 | kHz | |||||
Settling time | To 0.1% | 5-V step, ROUT = 5 kΩ | 1.8 | µs | |||
5-V step, ROUT = 125 kΩ | 30 | µs | |||||
NOISE | |||||||
Output-current noise density | 9 | pA/√Hz | |||||
Total output-current noise | BW = 100 kHz | 3 | nA RMS | ||||
POWER SUPPLY | |||||||
Quiescent current | VSENSE = 0 V, IO = 0 mA |
TA = 25°C | 25 | 45 | µA | ||
TA = –40°C to +125°C | 60 | µA |
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.
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:
or
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.
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.