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TLC5923 Channel 0 Not Working

Ryan Sturmer
Prodigy 30 points
Other Parts Discussed in Thread: TLC5923

I've got a TLC5923 wired up on a board to drive a couple of UV LEDs.  I have multiple channels, all of which work except for channel zero.  The wiring between channels is identical, The SPI mode I'm using (I believe) is correct, and I've adhered to all the AC timing characteristics called out in the data sheet  (I'm communicating with the device at an extremely slow rate, so the nanosecond setup times that are required for everything are more than satisfied)

Has anyone had a similar experience with this chip?  The behavior persists across several boards, so I don't think I've fried a channel.  Not sure what's up here.

-R

  • 0
    Prodigy 30 points

    Incidentally, I've read out the LOD register for the part.  I'm only using 12 of the channels, the remaining 4 are left open circuit.  The LOD correctly reports the top four channel as open, but reports channel zero as OK (no open circuit)  even though I get no light from my LED.

  • 0
    TI__Guru 58215 points

    Hello Ryan,

    Due to the fact that this behavior is seen on several boards, is it possible that this is caused by either the board layout or the soldering? If not, it would be helpful to get the schematic and layout to understand the issue a little more in detail.

    Best regards,
    Brigitte

  • 0 in reply to Ryan Sturmer
    TI__Guru 58215 points

    Hello Ryan,

    You should program the outputs you do not need to off mode. It should reduce the quiescent current when you do so. In addition normally you should no longer get a LOD warning on these channels.

    Best regards,
    Brigitte

  • 0
    TI__Intellectual 980 points

    Hello Ryan-san,

    My name is Narisawa and I'm in charge of LED driver and in development group.

    When you input doc correction data and on/off data and then TLC5923 can controlled each channels except channel zero.

    If it's so, data communication is no problem.

    To check channel zero issue whether IC or other, could you please check below thing?

    When input "on" data for all channels and then  channel zero pin is connected other worked channel.

    If LED which is connected channel zero is turned on, in this case channels zero is problem and wire is no problem.

    And if LED of other channel is turned on and taht brightness is increased, in this case, channel zero is no problem and wire connection of channel zero is problem.      

    Thank you for your cooperation.

    Best Regards

    K.Narisawa