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DRV8305: Current sensor output of DRV8305: Bias shifts

Kirancps
Prodigy 70 points
Part Number: DRV8305
Other Parts Discussed in Thread: CONTROLSUITE

I have a custom board with C2000 delfino MCU & DRV8305 for driving BLDC motors. The current sensor output of DRV8305 is fed to  ADC of Delfino MCU. When I'm reading the phase currents, The bias of the phase currents is varying sinusoidally.  Upon increasing the PWM frequency the bias shifts dissappearsand the current waveform is distorted. 

The schematic is almost same as DRV8305 boosterpack with sense resistor  modification. Any help in this regard is appreciated

Attached data was captured from ADC of C2000.

  • 0
    TI__Intellectual 2595 points

    Hi,

    I have a couple of quick questions to start debugging this:

    First, what is the modification you made to the sense resistor schematic?

    Second, what FETs are you using for the power stage?

    Finally, what IDRIVE setting are you using on the DRV8305?

    Thanks,
    Garrett

  • 0 in reply to Garrett Walker
    Prodigy 70 points

    Hi

    I am attaching the schematic of the DRV section.

    We are using AON7280 MOSFET for inverter (www.aosmd.com/.../AON7280.pdf)

    IDRIVE is set to 60mA.

  • 0 in reply to Kirancps
    TI__Intellectual 2595 points
    Thanks for the additional info! From your schematic, I'm not sure that this is a hardware issue, so I have a few new questions on the software side of things:

    1) Did you base your code off of an example project in controlSUITE, or is this your own code?

    2) Do you perform an offset calibration for the current sampling?

    3) Are you running your motor with a load, and if so, how much? Did you tune the Kp and Ki paramters of the speed/current regulator?

    4) Have you used open loop control to verify if the current sampling is correct?

    Thanks,
    Garrett