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Question on DRV8301

John J Wu
Genius 3870 points
Other Parts Discussed in Thread: DRV8301, BOOSTXL-DRV8301

I have a question regarding DRV8301 chip. The chip provides two shunt resistor amplifiers for current sensing. So one of the phases doesn’t have a shunt in such scheme.

Would you be able to provide me information or some application note showing how we can successfully resolve cycle by cycle current reading of all phases with only two shunt resistors?

  • 0
    TI__Mastermind 26065 points
    Hi John,

    In theory, the total current sum of the three phase will be Zero at any time. So you can always calculate the third current after you got the two by sensing. But this will need precise sampling time on the two phase with sense resistor, taking extra calculation, and may causing some unbalance since we get them by different ways.

    Most of our customer will add one external OpAmp for the driving system. You can refer to our EVM and boostpacks of DRV8301.

    Best regards,
  • 0 in reply to Wilson Zuo
    Genius 3870 points
    There is some issue in some phases. Imagine phase A and B have shut resistors and phase C doesn’t. Now if the current in some state runs from phase A, or B, (high sides) into C (low side), there are no means to measure current. For example if the motor is stalled in a state where such conditions happen, we can’t measure current and we won’t know.
    The method you are talking about can work for non-stalled motor to yield average current, and is not good for quick decisions.
  • 0 in reply to John J Wu
    TI__Mastermind 21320 points

    John,

    You are correct, as Wilson mentioned we generally add an additional current sense to the 3rd phase in applications that require it. You can refer to the BOOSTXL-DRV8301 design as an example.