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TPS65217: SYS output falls from 5V to 1.5V

Nicholas Carley
Genius 9895 points
Part Number: TPS65217
Other Parts Discussed in Thread: USB2ANY

My customer is using the TPS65217, the schematic is a copy of the beagle bone. The SYS output should be 5V, they are seeing this rail fall to 1.5V. This happens on two occasions:

  1. Immediately on power up
  2. After several hours of operation

Have we seen a similar issue before? Given that this rail powers all the other rails, what would you suggest we test/probe to better understand the root cause?

Thanks,
Nick

  • 0
    TI__Mastermind 30280 points

    Nick,

    VSYS=1-1.5V always happens for the same reason: VIO = 3.3V and the PMIC shuts down. VIO is back-feeding the VSYS pin, and there are multiple diode drops in this leakage path. It happens because VIO is supplied externally from another LDO or buck regulator.

    The same thing happens on the EVM when the USB2ANY is applied and supplies 3.3V without the PMIC turned on.

    During power-up, it typically means PWR_EN is never set high. After many hours of operation, it could be due to a fault on the PMIC. The PMIC shuts down, but the PMIC is not disabling the external supply for VIO.

    I hope this makes sense and helps you debug the issue.