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Edge trigger for PWRON

Antony Lin
Genius 13480 points
Other Parts Discussed in Thread: TPS65950

In DataManual, it's said that "The PWRON signal is debounced 1024 ´ CLK32K (maximum 1026 ´ CLK32K) falling edge in master mode."

Now if we press PWRON button to low before insert main battery (VBAT), the platform will swtich on when we insert VBAT.  Since the falling edge of PWRON happens before VBAT insertion, how does TPS65950 detect this as a swtich-on event?

THanks!

Antony

  • 0
    TI__Genius 15100 points

    Hi Antony,

    I would say insertion of VBAT is a pwron event and not pressing of PWRON (this is for the first start-up event). Under what conditions (or use case) do you think that PWRON will be pressed and the battery will be inserted?

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    TI__Genius 13480 points

    Hi Gandhar,

     

    Actually I tried this on my board with starton_vbat=0, and got this test result.  If I didn't press PWRON before/after VBAT insertion, the board is not switched on when VBAT is inserted.

    Antony

  • 0 in reply to Antony Lin
    TI__Prodigy 630 points

    Hi Antony,

          If you have configured starton_vbat=0, then it is natural that device will NOT switch on unless PWRON is pressed.

    I feel you have made a typing mistake and you meant that the board IS switching On when VBAT is inserted even though you have configured starton_vbat=0. Right?

    IF yes, then can you confirm you have made starton_vbat =0 for all three Processors ( P1,2,3)?. If not, this is the reason for seeing switch On.

    Incase you have done it for all three Proc, can you confirm if you have a backup battery present? Incase you do not have a back up battery present, even if you have configured starton_vbat=0, once you remove the main battery, registers will be reset and starton_vbat will be "1" again when battery inserted.

    If you have a backup battery, removing the main battery will mean that device goes into Backup state and the register settings will be kept. In this case, if you insert a main battery, you will not see a swtich on.

    Let me know if the above explanation ( although very long ) helps ..

    Regards,

    Kartik

  • 0 in reply to Kartik Sudarshana11777
    TI__Genius 13480 points

    Hi Kartik,

    Actually I set STARTON_VBAT=0 for P1, P2 & P3.  In addition, VBACKUP=3V -->  "STARTON_VBAT=0" configuration is kept by VBACKUP. 

    The test procedure is,

    1. Set STARTON_VBAT=0 for P1, P2 & P3. 

    2. Remove VBAT --> NRESPWRON becomes low

    3. Insert VBAT --> NRESPWRON keeps low (STARTON_VBAT=0 is kept by VBACKUP)

    4. Remove VBAT again.

    5. Short PWRON to GND.

    6. Insert VBAT --> NRESPWRON becomes high.

    7. Read STARTON_VBAT  value--> They are still low.

    Antony

  • 0 in reply to Antony Lin
    TI__Genius 15100 points

    Hi Antony,

    You actually found out a corner case where the device detects this as a trigger. The internal debounce logic resets when you press PWRON switch and thus sees the insertion as an edge and hence a starting event.

    I will update the errata document with this information.

     

    Regards,

    Gandhar.