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Problem with LM5069MM

David Zhang16358
Expert 1860 points
Other Parts Discussed in Thread: LM5069

I have two LM5069MMs on my design.

The problem is when I turn on the system power, one of LM5069 with 85uF load can be turned on sometimes and can't be turn on sometimes.

I have checked the Timer pin of LM5069 when it can't be turn on, it shows "low" always.

Please let me know any suggestions.

Many thanks.

  • 0
    Expert 1860 points

    My LM5069 is -1 device.

    I will try LM5069 -2device.

  • 0 in reply to David Zhang16358
    Expert 1860 points

    I have measured the Timer pin when system power turn on: it is always "low".

    But another LM5096 can be turn on each time.

    What is the reason for this?

    Any suggestions are appreciated.

  • 0 in reply to David Zhang16358
    TI__Genius 13245 points

    Hi David,

    When the device is first turned on, the timer will ramp up during the "insertion delay" period on all LM5069.  After the insertion delay period, the timer will then ramp during current limit or power limit conditions.  These can occur on startup with large capacitive loads.  When the timer reaches the voltage threshold, the device will pull the gate low.  If your device is a LM5069-1, then it will not attempt to restart.  If it is an LM5069-2, then will go through a retry delay period and attempt to start up again afterwards.

    If you are looking at a -1, then it has probably hit current limit or power limit on startup and is not retrying.

    Regards,

    Mike