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TPS65218: How to delay PMIC boot timing

Michi Yama
Guru 10030 points
Part Number: TPS65218
Other Parts Discussed in Thread: AM3354, , SN74LVC1G3157

Hi,

My customer considers to use TPS65218 with AM3354.

TPS65218 and AM3354 are in the same board( graphic board). But System power supply circuit is in another board(main board).

Customer would like to delay PMIC boot timing after system power is supplied to PMIC. The signal  for making delay timing  is only XPOR from main board.  XPOR signal is 3.3V and low active.

I know PB and PWR_EN signals can use for the change of TPS65218 boot timing. But PB input is required the falling edige. But XPOR is the rising edge (L --> H). So PB input can't use.

Also PWR_EN input is connected to AM3354. So PWR_EN also can't use.

Do you have any idea for delaying PMIC boot timing?  So  I have one question. Is it possible that XPOR signal connect to IN_BIAS pin? If this is possible, PMIC boot timing can be delayed by XPOR, I think.

But IN_BIAS pin is for Power. XPOR signal is 3.3V. Is it OK for IN_BIAS pin?

Please advise me.

I appreciate your quick reply.

Best regards,

Michi 

  • 0
    TI__Genius 9380 points
    Michi,
    We have a question about the delay. Is the delay required to allow time for the processor to come on line to bring up the PMIC when ready?

    If the processor is using PWR_EN then couldn't you add a pull up resistor and a capacitor to ground on the PWR_EN pin to delay power on similar to a POR input. When the processor comes on line then it's push/pull output would override the RC.

    Any other comments to help us understand the delay, reason for the delay and the amount of time needed for the delay would help.

    Thank you
  • 0 in reply to Gordon Varney
    Guru 10030 points

    Dear Gordon-san,

    Thank you for your quick reply.

    The delay is required AM3354 to synchronize with the main processor ( it is in main board, not graphic board). The only trigger signal is XPOR (Power on reset ). It comes from main board to graphic board (AM3354 board). So customer would like to use XPOR signal.  Is my customer's concern clear?

    Please give me your advise again.

    Best regards,

    Michi

  • 0 in reply to Michi Yama
    TI__Genius 9380 points
    Michi,
    I think I understand you question. I will ask the team and see if anyone has an idea on how to implement this.
  • 0 in reply to Gordon Varney
    TI__Genius 9380 points
    Michi,
    Take a look at part number SN74LVC1G3157. This is a SPDT analog switch.
    Connect TPS65218 PWR_EN to pin A. Pin B1 to GND. Pin B2 to AM3354. Pin S to XPOR.

    When XPOR is low PWR_EN is held low. When XPOR is held high, PWR_EN is connected to the AM3354.

    Think of it as the main controller can hold it low or hand off control to the AM3354.

    I think this will solve your problem. Let me know if you have any other questions or if you want to look for an alternate solution.