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Beaglebone based design: TPS65217b - not booting

Hi,

I'm working in a design based on the BeagleBone where we basically made small modifications and manufactured the board. When we received it and started the tests we found out that the PMIC is not even providing the necessary voltages to let the processor boot. We are powering the board with the USB cable.

VLDO1 and VLD2 are not outputing any voltage so our guess it that the PMIC is at the OFF operation mode.

In our design, we connected a simple (with a button) circuit to the PB_IN to be able to start the board from a Li-Po battery but we believe that this is causing trouble (see the picture attached).

Our guess is that PB_IN (push button input) is kept low and for this reason the PMIC is in OFF operation mode all the time.

We base our conclusions in the assumption that  VDD_3V3A (PB_IN is connected to VDD_3V3A) might be low because the PMIC is in OFF operation mode.

Does this make sense to anybody? Could anybode check our PMIC design and provide some feedback?

Any comments are welcome.

Thanks.

  • If you suspect the circuit connected to the PB_IN, then I would suggest start removing the pull up resistor to VDD_3V3A and the BJT one by one.  I am also suspicious about VDD_3V3A since it is an output of an LDO in the PMIC.

  • Thanks for your comment.

    I removed those two components and checked PB_IN. Surprinsingly it shows 3.39 V (even though VDD_3V3A is low, checked). So this is leading me to think that maybe the manufacturer didn't do a good job.

    USB_DC is for now the only line containing voltage so the only way those 3.39 V reached PB_IN is through short-circuits i guess.

    I'll keep looking into it. Let me know if something comes to your mind.

  • Hi again,

    After removing the BJT and the pull up resistor i kept doing test and I found something odd:

    • After the removing the componentes, once i plugged the USB cable, the board didn't show any sign of powering up so i was guessing that the PMIC should be dead. I grounded PB_IN again and again but the board still didn't show any sign.
       
    • Now, if PB_IN is grounded when the USB cable gets connected, surprisingly if I disconect PB_IN from ground, VLDO2 shows a pulse for about 10 ms.
      In this state, everytime i ground PB_IN it shows the same pulse (see picture attached)
    Any idea why this could be happening? Does this mean the PMIC transitions to the "WAIT PWR_EN" state? but then why it doesn't wait for the 5s time-out?