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TLC5951: characteristics of Clock inputs

Tino Ruland
Prodigy 50 points
Part Number: TLC5951

Hi,

I'm trying to use TLC5951 with AMPMAFB-33.0000 MEMS oscillator for Grayscale PWM clock signals, connected to GSCKR/G/B in parallel. As soon as the oscillator is connected to the TLC's pins, the clock signal breaks down, recovering after opening the connection again. So I wonder if the input pin's capacitances might be too high. Could you tell me the capacitances of GSCKR/G/B pins? In the datasheet it's only stated that the input current is maximum 1µA.

If this doesn't lead to a solution, do you recommend any spedcific oscillator IC to be used with the TLC?

Thank you very much for the support.

Best regards,

Tino

  • 0
    TI__Expert 3190 points

    Hi Tino，

    this device cannot be used as this. since the GSCLK need to stop after sending a frame data for the sequence. so I suggest to use a clock controlled source, like MCU, FPGA, etc. 

    Regards,

    Shawn

  • 0 in reply to Shawn Ding
    Prodigy 50 points

    Hi Shawn,

    thank you very much for the quick reply. However I'm not sure if I got you right. If I take a look at Figure 3 from the datasheet I cannot see a reason why the GSCKR/G/B shouldn't be running all the time. On page 26 it's stated that "The grayscale counter values are held at 0 while XBLNK is low, even if the GS clock input is toggled high and low", so I don't really see a problem there too.

    Could you please provide further explanation?

    Apart from this, do you see any reason why the oscillator output signal breaks down?

    Best regards,

    Tino

  • 0 in reply to Tino Ruland
    TI__Expert 3190 points
    HI Tino,
    You can see from Figure 3, there are a sequence restriction for the GSLAT and GSSCLK, Tsu2, and a sequence restriction for the XBLNK and GSSCKR/G/B, Tsu1. Also the Tsu3, Tsu4.
    You could not make sure to meet these time requirements if you use an uncontrolled oscillator.

    I don't know the specific reason why oscillator break down, I suggest to parallel a 50ohm resistor at the input of the GSCLK to see if this helps.

    Regards,
    Shawn