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Original question:

TPS65381A-Q1: power down Without WR_CAN_STBY

TPS65381A-Q1: PMIC always turns micro ON even though WR_CAN_STBY is sent from the micro

manoj devi
Prodigy 40 points
Part Number: TPS65381A-Q1

The micro employs wake/sleep up by either IGN(Pin 30) or CANWU(14) and takes the power from VDDIO(22) from the PMIC.

Wakeup – When either IGN or CANWU is high.

Sleep – When both IGN and CANWU goes low.

 When a sleep is intended for the micro, we set the following to PMIC,

  1. IGN Pin = Low.
  2. CANWU Pin = Low.
  3. Send the command WR_CAN_STBY from the Micro to PMIC.

First two steps can be interchanging.

I’m observing that the micro keeps receiving 5v at VDDIO(22) even though all the above 3 steps are met.

Do you think we need to perform any other steps to be able to enter sleep?

We are not modifying the IGN_PWRL in any of the steps. The PMIC is in Active state just before we initiate the sleep process.

  • 0
    TI__Mastermind 20590 points

    Hello Manoj,

    I believe you have a slight mis-understanding about the difference between IGN pin wake up and CANWU pin wake up.

    The IGN pin is normally not latched unless the IGN_PWRL is used.  So if only IGN is used without IGN_PWLR being set to one the device will power up when IGN is high and it will power down when IGN is low (assuming VBAT supply is provided continuously).

    However CANWU is a latch pin, so once it is detected high the device will stay on until the WR_CAN_STBY command is sent, level on IGN or CANWU doesn't matter once the CANWU_L bit is set and latched.

    If the level on both CANWU and IGN are actually low, IGN_PWRL but cleared to 0 (default) and the WR_CAN_STBY command is sent the device will power down to STANDBY state.  I have to speculate the pin levels may not actually be low, especially the IGN pin. Please double check the pin levels and software timing of WR_CAN_STBY with a scope or logic analyzer.

  • 0 in reply to Scott Monroe
    Prodigy 10 points
    Hello Scott,

    Thank you for the reply.
    I will double check the IGN pin. And what about the software timing of WR_CAN_STBY? As of now, the WR_CAN_STBY is sent after the IGN and CANWU is cleared.

    Does the IGN_PWRL get set by any means?

    From the micro-controller nothing specific is done to set the IGN_PWRL. Will it hold the default value or get set internal to the PMIC?

    Also is there a minimum threshold for the IGN voltage high?
    And, does the IGN need to be grounded? As of now, the IGN is floating when there is no high in that pin.

    Regards,
    Jithin
  • 0 in reply to Jithin John
    TI__Mastermind 20590 points
    Hello Jithin,

    The IGN_PWRL will not get set automatically, the software in the MCU must set this bit. One other configuration bit to check is the POST_RUN_RST bit.

    The IGN pin thresholds are in the datasheet, POS 7.1, IGN_WUP. Minimum is 2 V and maximum is 3 V.

    The IGN pin can be left floating, there is an integrated pull down, I_IGN.