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TPS65217: PMIC_EN pin not pulled high

Part Number: TPS65217

Hi,

I have a TPS65217C design that used the Beagle Bone as a reference design. In the reference design, the PMIC_EN pin is attached to the processor with no pull up resistor outside of the PMIC and that works well. I have a similar design that is not working. I did more research after my boards were not working (VSYS is stuck at 500mV) and realized that the PMIC_EN's default value is 0 which is what I get when I probe the pin on the board. How does the Beagle Bone setup work while mine doesn't? I am powering my board thorough the USB or the AC input. I also left the nReset pin floating and probing it gave me 3.3V.

Unfortunately, I do not have a breakup pin for the PMIC_EN. Would permanently shorting the enable pin with the AC pin next to it solve the issue or I would need a pull up resistor? Because of the pitch of the component, it is difficult to solder a breakout wire from the enable pin without shorting any of the adjacent pins. 

I have attached TPS65217's schematic 

8156.Power Management.pdf

  • Hi Taringana,

    The Beagle Bone board uses the AM335x to control the PWR_EN pin. The C6 pin output of the AM335x (PMIC_POWER_EN) appears to be a driven output by default (does not require an external pull-up source).

    If your PWR_EN pin is not pulling high at the correct time, I would investigate the AM335x datasheet or the AM335x Technical Reference Manual and step through the power up sequence to see where the first failure occurs. We also have an application note below about powering the AM335x with the TPS65217 that may be handy:

    Powering the AM335x with the TPS65217x . (Rev. I)

    The RTC is responsible for generating the PMIC_POWER_EN control according to the below clause in the Technical Reference Manual:

    To answer your question about shorting PWR_EN to one of the inputs, the PWR_EN pin can handle voltage up to VIN (VSYS as VIN I believe). As long as you don't drive PWR_EN to a higher voltage than your greatest VIN level, I think you can try shorting the pin to VSYSYou will want VSYS to be ready when PWR_EN is pulled up so that the regulators have power when they are enabled.

    Regards,

    James

  • Hi Taringana,

    I made some edits to my last reply so please take a look for the latest information.

    Regards,

    James

  • Hi James,

    Thank you for pointing me in the right direction. I realized that LDO1 was the issue as it was not going high with VSYS therefore PMIC_EN was also not going high. This was due to some DNP resistors that were populated during manufacturing that led to LDO1 being shorted to ground. The boards I had not used for testing before discovering this issues are running just fine. I will get the ones with the damaged TPS65217 back to the manufacturer and hope that a component swap will make them work.

    Thanks,

    Taringana