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TPS546D24A: Questions about relationship between VOUT_MARGIN commands and VOUT commands

Albert Sun
Intellectual 360 points
Part Number: TPS546D24A

Hi,

In theory VOUT_MIN<=VOUT_MARGIN_LOW<=VOUT_COMMAND<=VOUT_MARGIN_HIGH<=VOUT_MAX. If I intentionally set VOUT_MARGIN_HIGH below VOUT_MARGIN_LOW. What would happen? Does PMBUS allows this?

-A

  • +1
    TI__Guru 56775 points

     

    The TPS546D24A does not prevent the user from setting VOUT_MARGIN_HIGH lower than VOUT_COMMAND or VOUT_MARGIN_LOW in Relative or Absolute mode.  When OPERATION is set to switch to VOUT_MARGIN_HIGH, the output voltage will change to the value programmed in VOUT_MARGIN_HIGH, as long as it is within the bounds of VOUT_MIN to VOUT_MAX.  If VOUT_MARGIN_HIGH is outside of the mounds of VOUT_MIN or VOUT_MAX, the output voltage will be clamped at that lower or upper bound.

    PMBus does not explicitly prohibit VOUT_MARGIN_HIGH from being lower or higher than VOUT_COMMAND or VOUT_MARGIN_LOW, through many PMBus devices do limit the programming of VOUT_MARGIN_HIGH.

    NOTE: The TPS546D24A VOUT_OV and VOUT_UV detection hardware is implemented with relative hardware that auto-tracks changes to the output voltage, even when VOUT_MODE is in absolute mode, so changes to VOUT through VOUT_COMMAND, VOUT_MARGIN_HIGH or VOUT_MARGIN_LOW will scale VOUT_OV_WARN_LIMIT, VOUT_OV_FAULT_LIMIT, VOUT_UV_WARN_LIMIT and VOUT_UV_FAULT_LIMIT with the change in output voltage, whether VOUT_MODE is programmed for Absolute or Relative mode.