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Original question:

DRV8718-Q1: questions about test on DRV8718S-Q1 EVM

DRV8718-Q1: VDS overcurrent fault report

Elec Cheng
Expert 7055 points
Part Number: DRV8718-Q1

Hi Expert,

I am testing DRV8718-Q1 EVM and find GUI report VDS overcurrent fault. I only configurate two HBs but you can cee below that many channels report VDS overcurrent  fault. According to "8.3.8.8 MOSFET VDS Overcurrent Protection (VDS_OCP)" in d/s, it monitor  voltage across the VDS. But even during normal working, if PWM is 20kHz, the period is 50us. The duty cycle is 50%. So when high side is off and low side is on, it seems the H1 VDS overcurrent fault will still be triggered. Could you please explain the scheme of this. Thanks.

BR,

Elec Cheng

  • 0
    TI__Mastermind 24805 points

    Hi Elec,

    Thank you for your question.

    I recommend to try this procedure after you saw faults.

    1) Go to register map page.

    2) Set 00 for HB3/4/5/6/7/8_CTRL on address 0x09h and 0x0Ah. (To make sure HB3/4/5/6/7/8 are disabled)

    3) CLR_FRT

    4) Start driving motor again.

    regards

    Shinya Morita

  • 0 in reply to Shinya Morita
    TI__Expert 7055 points

    Hi Shinya,

    Thanks for your reply! I will test and try your suggestion. 

    Elec Cheng said:
    According to "8.3.8.8 MOSFET VDS Overcurrent Protection (VDS_OCP)" in d/s, it monitor  voltage across the VDS. But even during normal working, if PWM is 20kHz, the period is 50us. The duty cycle is 50%. So when high side is off and low side is on, it seems the H1 VDS overcurrent fault will still be triggered. Could you please explain the scheme of this.

    Could you please also explain about the mechanism of VDS overcurrent? I still have some confusion here. Thanks.

    BR,

    Elec Cheng

  • 0 in reply to Elec Cheng
    TI__Mastermind 24805 points

    Hi Elec,

    VDS overcurrent is monitoring VDS voltage of external FET while it is turning on.

    VDS = Rdson(FET) * I

    For example, If Rdson is 0.1 ohm and want to set over current 10A, 

    VDS threshold can be 0.1phm x 10A = 1V.

    regards

    Shinya Morita