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LP5860: About De-ghost Function

Ryu Yamashita
Genius 3685 points
Part Number: LP5860

Hi team,

On the evaluation board, when the anti-ghost lighting function is turned on, a reverse voltage exceeding the absolute rating is observed in the LEDs.
This is probably a natural phenomenon due to the anti-ghosting mechanism, but there is no mention of this in the datasheet.

The LEDs mounted on EVMs have an absolute reverse voltage rating of 5V, but there are many LED manufacturers that have deprecated this rating rather than the numerical value.
I would like to know how it is determined that the De-ghost function does not affect the LEDs in this regard.

Sincerely,
Ryu.

  • 0
    TI__Mastermind 20515 points

    Hi Ryu,

    For the LED driver with matrix topology scheme, it indeed exists reverse voltage problem since we need to figure out the ghosting problem. For your question, I think it's depend on the spec of LED. Or how to balance the reverse voltage on LED and de-ghosting function for users, if users care more about reverse voltage, they can disable the de-ghosting function to avoid the reverse voltage.

    BR, Jared

  • 0 in reply to Jared Zhou
    Genius 3685 points

    Hi Jared,

    Thanks for the reply.
    So you are saying that LEDs that cannot withstand reverse voltage cannot be used?
    By the way, do you know how much reverse voltage is generated?
    I would like to use the de-ghosting function, but I am concerned about using it because the current LEDs do not have specifications for reverse voltage.

    Sincerely,
    Ryu.

  • +1 in reply to Ryu Yamashita
    TI__Mastermind 20515 points

    Hi Ryu,

    Please refer the below comments for your questions:

    "you are saying that LEDs that cannot withstand reverse voltage cannot be used?"

    [Jared]: No and I think LED should has ability to withstand reverse voltage. But if the reverse voltage is relatively large and drop on LED for a long time, I think it will make some effect for LED.

    "By the way, do you know how much reverse voltage is generated? I would like to use the de-ghosting function, but I am concerned about using it because the current LEDs do not have specifications for reverse voltage."

    [Jared]: For LP5860, the reverse voltage can be adjusted by register configuration and the minimum is about 1.2V when enable both upside and downside de-ghosting.

    BR, Jared