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LM5008: Output Locked at 2V and can't recovery

leo xue
Expert 1595 points
Part Number: LM5008

Hello,

     Our customer is using LM5008,  with 60V input and 24V/200mA output.

     The output will lockout falling to 2V from 24V when the FB side is touched with a finger. This issue is that it can't recovery when moving the finger. the schematics refers below. please give a hand on this . thanks very much.

  • 0
    TI__Expert 6245 points
    Hello Leo,

    If the finger is also touching pin 6 bridging pin 5 (FB) and pin 6 (RON), the RON pin will see a small resistance to ground. If RON is pulled low the part is supposed to shutdown. If the finger is not perfectly clean, there may be enough residual leakage between these pins to prevent the part from properly recovering. See "On-Time Generator and Shutdown" in the datasheet.

    If this is your problem, please click "resolved" otherwise, reply to this thread so we can figure this out.
  • 0 in reply to Robert Blattner
    Expert 1595 points
    Hi Robert,
    Sorry for miss your message, I should clarify that the finger is not touching pin 6 bridging Pin 5 . So there is must be another factor. thanks
  • 0 in reply to leo xue
    TI__Expert 6245 points
    Have you tried reflowing or resoldering your part. Sometimes, a weak solder joint can cause problems like this. If impedances are similar to those in the recommended design, simply pressing with a finger should not disturb a design this way.