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LM3435: Thermal issue when LED open and PWM keep input.

daniel
Genius 5095 points
Part Number: LM3435

Hi Team,

We measured around 100C on the inductor when panel non-connect (LED open) and PWM keep input to G/B/R_CTRL pin.

If we disable PWM input, the temperature back to normal.

I am curious why there is no load, but cause high temperature.

And why PWM affect the temperature even if there is no load.

Thanks

  • 0
    TI__Mastermind 25500 points

    Hello Daniel,

    I am going to forward this to the expert on this device. Please be aware that it is the holidays and it is possible he will not respond until after the 1st, but hopefully you will get the help you need soon.

    Regards,

    Clint

  • 0
    TI__Expert 3920 points
    Hi Daniel,

    By disabling the PWM only, the converter is still switching and still provide an output voltage.
    It detects open LEDs, but does not shut-down or work in sleep mode.

    I suspect the converter is still running at a fairly high frequency so that you got hot inductor and device.
    If there is an intention of no LEDs connected, please pull-low EN to shut-down the device.
    If a test of open is conducted, please check the I2C register. Once found the open fault flag is up, shut-down the device by pull-down EN pin.

    I hope the above helps explain the situation.

    Thank you very much!