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TLC5971 min PWM pulse width

Frank D'Aliesio
Intellectual 715 points
Other Parts Discussed in Thread: TLC5971

I am having trouble finding the minimum pulse width for the TLC5971.  I see that it has 65536 pwm steps but can't seem to find the min pulse width.  Can anyone out there help with that?

Thank you,

Frank

  • 0
    TI__Guru 58215 points

    Hello Frank,

    The minimum theoretical pulse width is one pulse out of 65536 pulses. Dependent on the selection of the GS clock (internal or external), this minimum time is 1 SCKI pulse or 1 pulse of the internal clock.

    The internal clock has typically 10MHz (8MHz to 12MHz) and with the maximum value selected, this is 1/12MHz = 83.3ns.

    The maximum speed of the external clock is 20MHz, then the minimum on-time is 1/20MHz = 50ns.

    The typical rise time  of the outputs is 5ns and the typical fall time is 15ns, see datasheet page 6.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 20 points

    Hi Brigitte!

    You told the minium pulse width is 50ns (=20 MHz)

    So does that mean that the RGB- LEDs generally flash with a frequency of 12E6/65536 = 305 Hz?

    It seems that this IC is not suitable for RGB-LED propeller designs. :-( Or am i wrong here?

    What about the other TI LED-PWM drivers? Does one of them give a much higher output frequency?

    If not, do have any suggestion for me which LED driver IC to use for a RGB-LED propeller display?

    With regards,
    Diethart