SBOA534 February   2022 INA181 , INA240 , INA290


  1.   Introduction
  2.   Key Design Considerations


What are Current Sense Amplifiers?

Current sense amplifiers, also called current shunt monitors, are specialized differential amplifiers with a precisely matched resistive gain network with the following characteristics:

  • Designed to monitor the current flow by measuring the voltage drop across a sense element, typically a shunt resistor.
  • Tend to be easier to use, more precise, and less prone to noise.
  • Support currents from 10s of μA to 100s of A.
  • Natively-support common-mode voltages from –16 to +80 V and with additional circuitry up to 100s of volts.

System Benefits Addressed by Using Current Sense Amplifiers

  • Real-time overcurrent protection
  • Current and power monitoring for system optimization
  • Current measurement for closed-loop feedback

Key Parameters

Common Mode Range This specification defines the DC voltage range at the input of an amplifier with respect to ground. Current sense amplifiers are typically designed to support common-mode voltages well beyond the chip supply voltage. For example, the INA240 is capable of supporting a common-mode voltage between –4 V to +80 V while running on a supply as low as 2.7 V.
Offset Voltage This is a differential DC error at the input of the amplifier. Historically, to reduce the impact of amplifiers with high offsets, larger value shunt resistors were used to increase the measured voltage drop. Today, TI is able to offer current sense amplifiers with offsets as low as 10 μV, enabling higher-precision measurements at low currents and allowing the use of smaller value shunt resistors for improved system efficiency.
Gain Current sense amplifiers come with various gain options that have robust performance over temperature and process variations by integrating a precisely-matched resistive gain network. The gain options for fixed gain amplifiers vary from 0.125 V/V to 1000 V/V with gain errors as low as 0.01%.
Temperature Stability Current sense amplifiers integrate the amplifier along with all the gain-setting resistors which enables small and unified temperature drift. This allows for robust current measurements across the whole specified temperature range. The achieved temperature stability is one of the key advantages current sense amplifiers have over discrete implementations.

Analog Output
Integrates the full analog signal processing and provides a voltage or current output.
Digital Output
Integrates the full signal conditioning path and utilizes a standard two-wire digital interface.
Comparator Output
Provides a simple ALERT signal when the load current exceeds a threshold.
Integrated Shunt
Offers a low-drift, precision-integrated sense element.