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INA901-SP: Common mode error question

Anthony Cataldo
Prodigy 50 points

Part Number: INA901-SP

Tool/software:

Your space products catalog advertises this as an appropriate current monitor for motor control half bridge outputs. 

If you have a half bridge switch node that is rapidly switching from 0V to 28V, say at 10 kHz, and you want to sense current at that point, will this part handle those large common voltage swings at this rate without introducing significant error?

Have you done any testing in the lab for this kind of application?

Thanks.

  • 0
    TI__Mastermind 26095 points

    Anthony, 

    The INA901 does not have not any form of PWM rejection, so as you say, placing the device in line with the switch node would likely introduce error from common mode transition on the positive and negative edges of each pulse. For use in an H-bridge, I would recommend implementing the device on the high side or low side of the bridge. This comes with tradeoffs in the measurement placement, but this would stabilize the common mode voltage for the application. 

    This app note gives a good description of high and low side implementations as I discuss above.