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DRV3901-Q1: VREG switch status during power up condition

Vishwas H R
Intellectual 330 points
Part Number: DRV3901-Q1

Tool/software:

Hello team,

In my application due to HV supply current limit we have put resistor between PVDD diode and VREG to limit inrush current.

In the datasheet it is mentioned as VREG Switch will be normally closed.

So, during power up condition will the capacitor be charged from VREG switch? (because VVREG_THRS1 is 1.7V to 2.3V and excessive forward drop occurs only when PVDD is greater than at least 2.3V)

Thank you,

  • 0
    TI__Mastermind 18555 points

    Hi Vishwas,

    The VREG_THRS is with respect to PVDD, so the switch is disabled till PVDD - V-VREG_THRS1:

    Till then the charging is done through current limiting resistor and diode. Can you let me know if this answers your question?

    Best,

    Keerthi

  • 0 in reply to Keerthivasan Kumanan
    Intellectual 330 points

    Hello Keerthi,

    The switch will be disabled if PVDD-VVREG_THRS1 > VREG till then the switch will be closed and capacitor will be charged by switch right?

    Let's say initially PVDD is 1V and VREG is 0V. So, 1V - 1.7V < 0V that means switch will be closed right (because it is mentioned normally closed) and capacitor will be charged from switch which is a problem?

    The green color line is PVDD and red is VREG. This is when DRV3901 is not connected.

    Will it be same behaviour if i connect DRV3901? (at least during initial time is it same later after sometime when PVDD-VVREG_THRS1 < VREG like 0.6s the switch will be enabled)

    Thank you,

  • 0 in reply to Vishwas H R
    TI__Mastermind 18555 points

    Hi Vishwas,

    Maybe I am not understanding the question correctly, but it is PVDD-VVREG_THRS1 < VREG, so it will charge through the diode path till VREG caps charge to PVDD - VVREG_THRS1 and the switch closes. I didn't quite understand how PVDD can initially be 1 V, but if there were somehow the case, I will need to check what the behavior would be. I am not sure if PVDD_UV gates the switch or not.

    Best,

    Keerthi

  • 0 in reply to Keerthivasan Kumanan
    Intellectual 330 points

    Hello Keerthi,

    I got confused. During the case PVDD is 1V and VREG is 0V the internal switch will also not work right because internal circuits will be turn off initially. So, it will charge from diode and resistor till it reaches PVDD - VVREG_THRS1.

    Thank you,