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Original question:

LM3549: Solution selection for keyboard

LM3549: LM3549 multi-ch open/short detection

Kami Huang60
Genius 3830 points
Part Number: LM3549

Dear Sir/Ms.

My customer tested the function of Open / Short in RGB detection, there seems to be a problem?
I remember to cooperate with the Enable signal? May I cooperate with the Enable signal, right?
If multiple channels are Open/Short at the same time, how to distinguish single channel or multiple channels on the LM3549 register? Do you need to cooperate with R_EN/G_EN/B_EN Pin? Is there a priority order to detect, and if it occurs at the same time, if it is detected first If there is a problem with R, FAULT will also be pulled Low?

Best Regards,

Kami Huang

  • +1
    TI__Genius 9255 points

    Hi Kami,

    The following PIC shows the PWM timing for LM3549. As we can see, LED is turned on when the respective enable bit is active. Open fault is generated when at the end of color. For example, which means that it will detect the OPEN red led when multiple channels are open during turning on period of red led. And the open/short fault bit will be covered by next color detection. So you are right that the detection of open/short function cooperate with R/G/B_EN pins.

    Best Regard 

    Monet Xu