SBOA534 February   2022 INA181 , INA240 , INA290

 

  1.   Introduction
  2.   Key Design Considerations

Key Design Considerations

High-Side Measurements

Sensing between supply bus and load.

System Advantages:

  • Able to detect load short to ground
  • Current is monitored directly from the source
  • High immunity to ground disturbance

System Challenges:

  • High bus voltage limits the availability of high input common-mode voltage devices

Advantages Over Discrete Current Sense Circuit:

  • Integrated gain resistors provide excellent matching to enable higher performance
  • Reduction in board space requirements
  • Unique input architecture allows for the common-mode voltage to greatly exceed the device supply voltage

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Low-Side Measurements

Sensing between the load and ground.

System Advantages:

  • Simple to implement and low-cost solution
  • Wide range of available options

System Challenges:

  • Difficult to detect load short to ground
  • System ground disturbance by the shunt resistor

Advantages Over Discrete Current Sense Circuit:

  • Integrated gain resistors provide excellent matching enable higher performance
  • Reduction in board space requirements
  • Sense a true differential measurement across the shunt resistor
  • Lower VOFFSET saves system power by enabling the use of smaller value shunt resistors to achieve the same error level

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In-line Measurements

Sense current in-line to the load.

System Advantages:

  • True phase current at all times reduces phase-to-phase errors
  • Best current feedback for greatest accuracy

System Challenges:

  • PWM common-mode voltage seen by amplifier
  • High common-mode voltage combined with high dV/dT poses steep challenge to many amplifiers

INA240 Advantages Over Discrete Current-Sense Circuit:

  • Enhanced PWM rejection provides high levels of suppression for large common-mode transients (dV/dT) in systems that use PWM signals

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