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TPS65916: PMIC On Request Generation Via Powerhold

Raja Ashutosh Kedia
Intellectual 430 points
Other Parts Discussed in Thread: TPS22965, TPS54620, TPS65916

Hi,

As per https://e2e.ti.com/support/applications/automotive/w/design_notes/3470.how-should-i-enable-and-disable-the-pmic , it is recommended to use POWERHOLD (GPIO_5) signal to enable PMIC. Hence, we plan to pull this signal high to D3V3 input supply (which is also the input to the TPS22965 load switch enabled by REGEN1 signal) so that On request is generated as soon as D3V3 supply is up.

Further, as per https://e2e.ti.com/support/applications/automotive/w/design_notes/3472.what-voltage-can-the-open-drain-gpios-be-pulled-up-to , it is recommended not to pull-up any GPIOs to a voltage, which is active before PMIC is ON. Hence, as per this, we understand that we need to pull the D3V3 supply from TPS22965 output (and not input) and this would not turn on the PMIC. Is this comment not applicable for POWERHOLD (GPIO_5) signal? Otherwise, how is it possible to Switch ON the PMIC with POWERHOLD signal.

FYI, we are not using PWRON pin and is left floating. Please suggest on the recommended connection for POWERHOLD signal and how can the PMIC be enabled.

Regards
Raja

  • 0
    TI__Genius 16410 points
    Hi Raja,

    The recommendation to not connect any open-drain GPIO to an always-on supply is only meant for open-drain outputs. This is because it can cause the output to glitch while supply is ramping, since the outputs are only driven low after OTP is loaded, 6ms after POR.

    For GPIO_5 / POWERHOLD input, you certain can (and must) connect this to a signal which is available before the PMIC is on. Connecting this to supply is ok. But please note that you will want a mechanism to complete the power-off sequence when power is unexpectedly lost, to comply with the processor power-off sequence. One way to do this is to use a PGOOD or supervisor from the input supply and connect that to POWERHOLD.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Intellectual 430 points

    Dear Karl,

    Thanks for the quick response.

    In our design, we are generating D3V3 supply using TPS54620 device and its PGOOD is pulled up to the D3V3 supply using a 10K resistor. As per your suggestion, we plan to connect the same PGOOD signal to the POWERHOLD (GPIO_5) pin of TPS65916 PMIC. Please confirm, if this is right.

    Regards

    Raja

  • 0 in reply to Raja Ashutosh Kedia
    TI__Genius 16410 points
    Hi Raja,

    Yes, that sounds correct. The assumption is that PGOOD will be pulled high when the TPS54620 output is valid, and when it goes out of regulation the PGOOD will be pulled low.

    Regards,
    Karl