• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 200 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65217CEVM: PMIC goes into off state after 8 second PB_IN signal at boot up

Matthew Wroe
Prodigy 20 points
Part Number: TPS65217CEVM

HI,

I have a design that is based on the Beagle Bone Black reference circuit.

The device will always be powered by a 5V DC supply and will be inaccessible once installed. I need to be 100% sure that if there is power connected the device always attempts to boot up from the off state.

I have found a condition where this is not the case and the PMIC doesn't appear to follow the design functional modes flowchart given in the datasheet page 39.

If the power is applied with PB_IN held low for greater than 8s, the PMIC goes to active state and then does a forced reset after 8 seconds.  If PB_IN is then released the PMIC appears to go to the off state.  V_SYS is low, LDO1 is low despite VIN being 5V continuously.  This is contrary to the flowchart which suggests that after a reset the PMIC will always reboot.

Is there a way of preventing this behaviour?

In my application this is happening due to a hardware watchdog circuit that is resetting the PMIC via the PB_IN input.

Thanks for your help.

  • 0
    TI__Mastermind 30260 points

    The reason is because the BAT, BAT_SENSE, and TS pins are all floating on the BeagleBone Black.

    Short BAT_SENSE to BAT and pull both of these pins to GND through a 1kOhm resistor. Pull TS down to GND through a 10kOhm resistor.

    Let me know the results when you try again.

  • 0 in reply to Brian Berner
    Prodigy 20 points

    Hi Brian,

    Thanks for replying.  I have tried your suggestion but unfortunately this has not made any difference on my application.

    My problem specifically only happens when the power button is held low when power is applied.

    This scope image  depicts my problem nicely.  PB_IN is held low while AC is applied.  The SYS voltage goes high and the power on sequence is initiated correctly.  After 7.5 seconds the device resets and SYS goes low again.  PB_IN is released after 11.5 seconds yet SYS stays low indefinately until PB_IN is pressed again.

    Thanks again for your help.

  • 0 in reply to Matthew Wroe
    TI__Mastermind 30260 points
    Please re-take the scope shot and zoom in on the time between SYS going low and PB_IN going high.

    Instead of measuring PGOOD, please measure BAT pin.

    The four channels probed will be AC, SYS, BAT, and PB_IN.

    What you would be looking for is anything that occurs 1 second after SYS goes low. If you don't see anything on BAT, then measure nRESET.

    Holding nRESET will keep the PMIC in reset until nRESET is released + 1 second.