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TPS65288 Overcurrent detection

AndyP
Expert 1756 points
Other Parts Discussed in Thread: TPS65288

Hello,

I have some problems with TPS65288 when turning on one of the bucks (buck 1). The buck 2 & 3 are enabled first, and later on buck 1 is turned on from MCU (EN1 goes high). The problem is that when the buck 1 load is fully discharged, after turning it on (about 20ms after EN1 goes high)  the whole PMIC goes off (all three bucks) for about 20ms, and then retries turning on the bucks. It seems to me that buck 1 detected overcurrent condition (lasting more than 10ms) and the device hiccup mode is entered.

My questions are:

- is there a way to tell if there is overcurrent condition?

- is there a way to get around this (manipulating enable, slow-start, current limit)

Any help is greatly appreciated

Best, Andy

  • 0
    Expert 1756 points
    There is also a "Soft start timer 10ms watchdog" mentioned on the Fig.49 in the datasheet, but there is no info what is the purpose of this watchdog.
    Is there a requirement that all the outputs must be at valid voltages in 10ms or less? When this timer starts counting? Is there only one global timer or three separate for all the bucks?

    This Fig.49 has some more unknowns for me, like "Enable discharge 10-12ms", and "Pre-bias timing 4-5ms". Could someone explain, how those timeouts work together?

    It feels that the datasheet should be much more informative.

    Best, Andy
  • 0
    Expert 1756 points
    Problem resolved.
    Buck 1 was overcompensated (Cc value too big), and output 1 start time was very long (tens of millisecond). So probably the soft-start watchdog kicked-in, and the device turned off.
    Still, I think that the datasheet could be more detailed about such behavior.

    Best regards,
    Andy