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TLC5958: OUTxn not working as expected.

Anonymous
Anonymous
Guru 17045 points
Part Number: TLC5958

Hi,

I've done some digging through the forums and referenced the sample code, datasheet and appnote. I am running into a problem where the driver is being correctly programming (I checked the FC1 and FC2 using a read) and producing the expected SOUT when latching in data for the memory, but as soon as I send my VSYNC, pause and start the GCLK (knocked it down to 1MHz), the test LED I have connected does not turn on. I am programming the memory with 0xffff ffff ffff as a test and connecting the OUTR0 to a red test led. I am using the correct orientation as referenced in the designs.

Can someone suggest some other debugging techniques, or help me debug this? I would prefer to use this chip instead of build my own led driver.

Thanks,

Lys

  • Hi Lysny,

        Can you share some waveforms of your problem?

  • Anonymous
    0 Anonymous in reply to Charles-Chen

    Hi Charles,

    I don't have access to the chip right now, but the waveform for the OUTxn was a constant voltage at ~2.2V or ~1.8V if I flipped the led in the incorrect orientation. The SOUT/SIN/SCLK all matched the app note. I doubled checked that the value I was writing to the FC register was the same as when I did a read command.

    If I don't have all the OUTxn's hooked up the LEDs, will the LOD info stop the driver from driving? That is the only portion I don't really understand.

    Thank you!

    Lys

  • Hi Lysny,

        LOD data output by the detection circuit are valid only during the ‘on’ period of that OUTXn output channel. The LOD data are always ‘0’ for outputs that are turned off. So it will not stop driver from driving if you have turned off the unused channels.