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TPS92511: TPS92511 output current issue

Mason Noh
Expert 2490 points
Part Number: TPS92511

Hi TI expert~

I have been using TPS92511 .

It is supposed to drive the load of 71mA constant current. (@Vin:40V, VLED:36V, RIADJ:21kohm)

However, after several seconds, the output current decreases on several board. (71mA-->52mA)

I measured LX pin and find out switching waveform is changed.


switching frequency: 300kHz

Could you let me know why? How can I improve this issue?

  • 0
    TI__Mastermind 25500 points

    Hello Mason,

    It looks from the waveform that the LED stack voltage drops some as it heats and you start going into DCM mode. This device loses accuracy when it enters DCM and is meant to run in CCM mode as described in the datasheet.

    This would be easy to check, just increase the switching frequency and/or increase the inductor value and it should not happen.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Expert 2490 points
    Thank you for your supports.
    I solved this issue.