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TPS53681: First Power Up functionality

Cosmin P
Intellectual 1690 points
Part Number: TPS53681

Hello,

In customer's aplication, a new manufactured board is powered up by applying the main 12V which turns ON the auxiliary supplies 3.3V, 5V etc.

In the next step all PMBus components on the card will be programmed.

The concern is for an unprogrammed 53681 to be disabled by default; switching should not occur for the load to be protected
Is the part coming unprogrammed, or if it is programmed, does it need to have xVR_EN actively pulled down to avoid a rail start-up?

Thank you

  • 0
    TI__Genius 11095 points

    Hi Cosmin, The TPS53681 comes pre-programmed with default values stated in the datasheet. The default is VR_EN active high. The VR_EN pins should be held low to prevent switching prior to programming .

  • 0 in reply to Matt Schurmann
    Prodigy 130 points

    Hi Matt,

    Thanks for your answer as I have similar questions.

    To add 2 questions for similar case: 

    1. The pre-programmed voltage is 0.5V (VOUT_COMMAND) for both channel A and B.

    If the load is higher, say 0.8V, 0.9V, do you see if any potential issue for the first time programming if VR_EN is enabled high?

    2. If the TPS53681 is programmed to be 0.8V, next time, we want to do voltage margining test to be powered up at 0.85V, should the VR_EN held low to program or it is safe to program with VR_EN enabled high when re-programming?

    Thanks,

    -Wei

  • 0 in reply to Wei Liu89
    TI__Expert 5830 points

    Hi Wei,

    1. The pre-programmed voltage is 0.5V (VOUT_COMMAND) for both channel A and B.

    If the load is higher, say 0.8V, 0.9V, do you see if any potential issue for the first time programming if VR_EN is enabled high?

    No issue, as long as pre-programmed VBOOT is < absolute maximum voltage of the load, it should be fine.

    2. If the TPS53681 is programmed to be 0.8V, next time, we want to do voltage margining test to be powered up at 0.85V, should the VR_EN held low to program or it is safe to program with VR_EN enabled high when re-programming?

    In this case, to change VBOOT to 0.85V, VR_EN  is not required to be low, however, the new VBOOT will be effective after VR_EN is toggled.

    Thanks

    Chasel

  • 0 in reply to Chasel Chen
    Prodigy 130 points

    Thanks Chasel.

    This resolved my questions.

    thanks,

    -Wei