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LM2611 locking up after short circuit event

MichaelH
Intellectual 350 points
Other Parts Discussed in Thread: LM2611

Hello,

   I have a problem where the LM2611 inverting Cuk converter is locking up after a short circuit event.  After a short, it current-limits the upstream power supply (set to 200mA) and stays that way until it is power-cycled.  The circuit I am testing is the TI LM2611 evaluation module board with the 10k feedback resistor replaced with a 20k resistor to give me -3V and the C_cuk replaced with a 100V 1uF capacitor.

   The datasheet makes no mention of short circuit protection, is there a way to make this switcher handle short circuits gracefully?

  • 0
    TI__Genius 16025 points

    Hi Michael,

    I've received your request and currently working on it. I will revert to you shortly.

    Thanks,

    Anston

  • 0 in reply to Anston Lobo
    Intellectual 350 points

    Hi Anston,

      Thanks for getting picking this up so quickly.  Extra information: I'm using a 50-ohm resistor for a load.  The chip doesn't seem to have a problem recovering if there's no load.  My upstream supply is 3.3V.  I'm testing the shorting behavior by using a jumper to briefly short the terminals, then removing the short.

    -Mike

  • 0 in reply to MichaelH
    TI__Genius 16025 points

    Hi Michael,

    You are correct. This part doesn't have built in short circuit protection. But it does have current limit protection. Your input is clamped to 200mA and this could be the source of the problem. The current limit doesn't trip until it breaches the 1.2A or .9A (Grade A or B) limit. Try this short circuit experiment by clamping the input supply to 1.5A. Let me know if it works. Also, How would you like the part to behave in the event of a short circuit? Shut down the output (as a protection element) or restart the part (regulator).

    Thanks,

    Anston

  • 0 in reply to Anston Lobo
    Intellectual 350 points

    Hi Anston,

       I increased the current limit on the bench power supply to 1.5A, and now it recovers.  It seems like the issue is that if a short circuit browns out the upstream power supply lower than the 2.7V minimum input voltage, it will latch and continue to draw maximum current even after the short circuit has been removed, preventing the part from recovering. I would like the part to shut down or current limit the output in a short circuit condition, but restart when the short circuit is removed instead of continuing to shunt maximum current.  

  • 0 in reply to MichaelH
    TI__Genius 16025 points

    Hi Mike,

    I'm attaching a circuit that if you place on your input will provide the latch off ability. In the event of a short circuit the Rsense resistor will bias the gate of the PNP to turn on and bias gate of the NPN to shutdown the part. The pull up resistor can be about 10Kohms. 

    This should provide a reset circuit that meets your needs. 2438.[E2E] LM2611 Latch off circuitry.pdf

    Thanks,

    Anston