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TLC5957: Output Channel Rise Time

ArTzy
Genius 13989 points
Part Number: TLC5957

Hi Experts,

Good day.

Customer is using the TLC5957 and noticing some unexpected voltage rise characteristics of the output channels. See attached images of the rise/fall characteristics of the voltage measured at one OUT channel driving a purely resistive load.

Can you help to explain the observed transition from a fast voltage rise to a slow exponential rise after the first 1-2 volts?

Any details you can provide about the internal circuitry of the TLC5957 driver would be helpful.

Thank you.

Regards,
Archie A.

  • 0
    TI__Genius 15776 points

    Hi Dear E2E users. Since April 3rd to 5th is Chinese "Qingming" Holiday, our expert will reply your question on April 6th. Thanks for your understand.

  • +1
    TI__Genius 12915 points

    Hi Artzy,

    Basically the outputs of TLC5957 are current sink, with a open-drain structure. At the voltage rise stage, the channels are all off and the net should be float. It is slowly driven up by the leakage current. TLC5957 do nothing at voltage rise time and the exponential characteristic should relate to the parasitic capacitance from board.