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TPS53319: Rmode - maximum soft-start time?

Vladimir Vuksanovic
Prodigy 30 points
Part Number: TPS53319

Table 3 of the TPS53319 datasheet shows Rmode range from 39K to 475K, selecting the soft-start time tss in the range of 0.7ms to 5.6ms.

Is it possible to use a higher value for Rmode to get slower startup, for example Rmode=750K for tss~9ms ?

Thanks.

  • 0
    TI__Mastermind 22756 points
    hi Vladimir,

    I don't know this part in detail, but I dread it won't work because the voltage on Rmode pin is sampled and holded at the start-up.
    You can increase the value of Rmode to increase the SS time but at certain point the linearity will stop (kind of saturation curve) as the pin voltage approaches the max V the internal DAC can manage...
    a typical SS time is anyway <5msec... what is the need for such long SS time?
    if it is only for "delay" purpose, you can act on the EN / UVLO with a sequencer or a passive network

    hope this helped a bit
    KR
    Vincenzo
  • 0 in reply to Vincenzo Pizzolante
    TI__Guru**** 191445 points
    I do not know that part real well either, but I am reasonably sure those are discreet SS time values. Not possible to select any times other than those listed.
  • 0 in reply to Vincenzo Pizzolante
    Prodigy 30 points

    Thanks for your replies guys, you are right about Rmode.

    In the meantime, I tried with a higher resistor value, and there was no change in soft start time.

    I was trying to reduce the inrush current at startup.