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rectifier MOSFET for TPS40077

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: TPS40077

I have a question about TPS40077.

In TPS40077 datasheet, there is a description that Si7336ADP(Vishay) can be used for rectifier MOSFET at reference specification(page.23). It's total gate charge is 50nc(MAX) under Vgs=4.5V condition.

Further, there is the following description in TPS40077 datasheet(page.12). "For proper operation, the total gate charge of the MOSFET connected to LDRV should be less than 50 nC." Is this description under Vgs=4.5V condition?

I think I have to select MOSFET less than 50 nC under Vgs=8V condition at reference specification(page.23), because LDRV output voltage is 8V(=DBP voltage).

  • 0
    TI__Genius 17240 points

    Hi Kensuke,

    I think the 50nC LDRV gate charge is under the minimum gate drive voltage. Although DBP is 8V typical, that is when VDD>10V. If the UVLO is programmed to be much lower, e.g. 4.5V, then the part will be powered on when VDD=4.5V, then DBP is only 4.3V typical.

    Regards,

    Na

  • 0 in reply to Na Kong
    Guru 29720 points

    Thank you , Na.

    In reference design(page.23), UVLO is 6V(NOM).So, I see 50nC is the target value.

    I think additional consideration is done in datasheet , about 130ns requirement and Cgs/Cgd(page.28) for  proper operation.

    Regards,

    Kensuke