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Original question:

TLC5940 not working properly

TLC5940: Powering the TLC5940 some LED goes on while some are off.

Rompel Schichtlem
Prodigy 220 points
Part Number: TLC5940

Hallo,

I have made a designed base on a daisy chain of 15 TLC5940.

The project is working since about 1 years whitout problem. But today when I power on the board, it happens that one LED was on and the remainder was off which has never happened.

I keep on wondering what could be the cause. i made all the measurement on all the input signal the look quite ok.

The LED is power with 5V and connected to the TLC5940 which is power with 3,7V. Could this be the problem??

When power the TLC5940 with 3,7V, what is supposed to be the output voltage of the OUT0-OUT15, when the driver if off? Because I am measuring different voltage on different pin ranging fromm 2,65V to 3,7V on the same TLC5940

  • 0
    TI__Genius 12915 points

    Hi Rompel,

    It is OK to power TLC5940 and LEDs with different power line. When the driver off, all outputs are float so that the voltage on outputs is different.

    Here are some confusion that I want to confirm. 1) Was this 'ON' LED always a specific one or just random one? 2) Was this abnormal behavior happened at all 15 drivers or a specific one? 3) Have you replace the abnormal IC and LED to see if it still happen?

  • 0 in reply to Hardy Wu
    Prodigy 220 points

    Hi Wu,

    thanks for your feedback.

    On LED ist random and appear on some driver and not at all driver.

    Depnding on the product use, we are having usually different constellation and it could be red, or blue ans some time even the greend one.

    When replacing the driver with a new one the issue disappear.

    Waiting for the feedback and thanks in advance.

  • 0 in reply to Rompel Schichtlem
    TI__Genius 12915 points

    Hi Pompel,

    I think the former IC was damaged somehow. If you need some further failure analysis, you can contact your local sales or FAE for it.