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DRV8305: DRV8305 SPI failed to work

Fougison
Prodigy 30 points
Part Number: DRV8305

DRV8305 SPI fails to work(I can't recive any data from the pin SDO,no matter what I send into), but the voltages of the pin DVDD, AVDD, VCPH, are all ture. When I disable the charge pump by removing one of the capacitors, the SPI begins to work(I can read or write the register correctly. I replace the DRV8305 many times, but the test result is the same. what is the issue? Thanks!BLDC_Diver_TI.pdf

  • 0
    TI__Mastermind 19720 points
    Hi,
    What voltage were you reading on PVDD, AVDD, VCPH when the SPI was working and when it was not working? Also we recommend that you use a 10K pull up on the nFAULT pin.

    regards,
    Michael
  • 0 in reply to Michael.Walker
    Prodigy 30 points
    Hi, Michael
    PVDD = 24V, AVDD = 5V, DVDD = 3.3V, VCPH = 0,when I removed one of the flying capacitors and then SPI work. PVDD = 24V, AVDD = 5V, DVDD = 3.3V, VCPH = 35V, when the flying capacitor was soldered and the SPI didn't work. I recognized lack a resistance for the nFAULT pin, but is it very serious?
  • 0 in reply to Fougison
    TI__Mastermind 19720 points
    Hi,
    I think the issue that you are having is that you CP2 cap is not rated for high enough voltage. From the datasheet:

    "CCP1 0.047-µF ceramic capacitor rated for PVDD
    CCP2 0.047-µF ceramic capacitor rated for PVDD × 2"

    Try changing the voltage rating on CP2 to be 50V.

    the lack of resistance on the nFAULT pin is not very serious.

    Regards,
    Michael
  • 0 in reply to Michael.Walker
    Prodigy 30 points
    Hi, Michael

    I don't have 0.047uF ceramic capacitors rating to 50V here now. I will buy some to change the CCP2.
    I tried to change the PVDD to be 6V, and then the issue was solved. So I think you are ture.

    Thank you very much.

    Fougison