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TPS659037: PWRDOWN pin delay

KKF
Expert 4295 points
Part Number: TPS659037

Hi PMIC team,

My customer is using TPS6590378, PWRDOWN is configured as active High, SWOFF_DLY is set to 0 and they want to trigger a power cycle using Sitara processor. However, they observe that pulling PWRDOWN pin high for 8ms does NOT trigger a power cycle. If they increase the high-time to 16ms, the TPS6590378 initiates a power-down sequence. Following questions arise:

   Is there some debounce filter internally for this PWRDOWN input?

   What is the minimum pulse time needed for PWRDOWN pin, in order to do a power cycle of PMIC?

   How much can this minimum pulse time vary between different devices and in worst case?

Thanks & best regards,

KF

  • 0
    TI__Genius 10000 points

    KF,

    How long after you turn on the device are you trying to turn off the device? Once the device is turned on, it takes up to 15ms for OTP settings to load and power up. Then the device is available to shutdown. Can you scope how long the device is on?

    Also, how are you turning the device on? Which pin?

    PWRDOWN has a typical 2ms debounce time.

    Thanks,

    Nastasha

  • 0 in reply to Nastasha
    Prodigy 30 points

    Hello.

      It does not matter the time for turning off using PWRDOWN, after turning on. It can be even minutes.

     PWRON and RPWRON methods for ON request are not used (PWRON Not Conn., RPWRON tied to 1.8V = SMPS8). For power-ON, the device is powered by 3.3V; after 3.3V stabilization the RESET_IN pin is released and device powers on.

     In our design we want to trigger PWRDOWN using RESET_OUT from Sitara, which is a 7.6ms pulse. Applying this at PWRDOWN does not trigger a powercycle. Using a signal generator and triggering PWRDOWN with a 20ms pulse, does indeed trigger a powercycle of PMIC.

    So I believe the 2 following questions still remain:

    What is the minimum pulse time needed for PWRDOWN pin, in order to do a power cycle of PMIC?

       How much can this minimum pulse time vary between different devices and in worst case?

  • 0 in reply to Florin S.
    TI__Genius 10000 points

    Florin,

    It looks like I misspoke on this topic originally. In further discussion with the team, there is a 15ms debounce time on the PWRDOWN pin. We do not have a maximum spec for this item. For a faster shutdown reaction, I recommend using RESET_IN or POWERHOLD to turn off the device.

    Thanks,

    Nastasha

  • 0 in reply to Nastasha
    Prodigy 30 points

    Hello,

       Thanks for the clarification. I'm focusing now to extend the pulse width with a monostable circuit.

     

    About the debounce on PWRDOWN pin being 15ms,  I couldn’t find this information in the datasheet or application notes.  Where is this documented please?

    Is this debounce fixed or SW programmable ?   If SW programmable, what registers?

     

    I need this information to properly dimension the pulse extend circuit.

     

    Thanks a lot!

     

    P.S.:       1. PMIC device code we’re using is TPS6590378ZWS.

                    2. There is no debounce time mentioned in the PMIC datasheet Table 5-11. Is that correct?

     

     Regards,

      Florin

  • 0 in reply to Florin S.
    TI__Genius 10000 points

    Florin,

    Hi, this is a fixed debounce, not programmable. I noticed as well that it is not clearly documented anywhere. I have flagged this as something to include in the next datasheet revision.

    Thanks,

    Nastasha