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DRV8412 VReg unable to start

Wee Chang Liew
Prodigy 100 points
Other Parts Discussed in Thread: DRV8412

We're experience some issues on the DRV8412.

We have a board where the DRV8412 can't be control by the PWM input. After some investigation, we found that the VReg of the DRV8412 is not 3.3V. Repeatedly power cycle, VReg always can't start, it measured 0.6V. At this point, we also observed voltage different between AGND and GND is 0.2V.

Also, we realised that if we do power recycle very fast, like within 0.5s, then VReg will start normally, and the PWM can drive the motor.

Observed that at the beginning the Vreg is at 0.6V, once power down condition happens, it raised to 3.3V and then dropped according to the VDD.

We then think that perhaps the chip has been damaged and make an effort to replace the DRV8412, but it has no help.

We somehow looking into resistor value between AGND and GND. Tried to increase the resistor value from 1 ohm to 10 ohm. And the VReg can start properly with fast power up and slow power up.

Anyone has any experience on this? What is the relationship between AGND and GND within the chip?

Thanks in advance!

  • 0
    TI__Guru** 114905 points

    Hi Wee Chang,

    Does this occur on multiple boards? Can you provide a schematic?

    Please refer to LINK for answers to your question about the relationship between AGND and GND

  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hi Rick,

    Thanks for prompt response. It happens to multiple board, the failure rate is close to 10%.

    Please find the schematics snapshot here:

    Also, the layout snapshot:

    I have M0,M1,M2, OC_ADJ linked to AGND, 1 ohm resistor from AGND to GND.

    I read the LINK, I understand the different between AGND and GND, just I can't understand the mechanism of VREG failed to start and AGND appear to have 0.2V higher than GND when VREG failed to start.

    I have 2 chips in one board, it always failed at 1 but not the other. This also puzzled me.

  • 0 in reply to Wee Chang Liew
    TI__Guru** 114905 points
    Hi Wee Chang,

    Can you clarify your statement I have 2 chips in one board, it always failed at 1 but not the other."?

    Does the failure occur at only one site on the board? If so, did you provide the snippet of the failing location?

    Can you also provide a scope capture of the failure? Please capture the rising edge of power, and VREG.