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TLC5940: After running sometime with LED brightness increasing and decreasing, then TLC5940 died out

Yap Tsi Searn
Prodigy 220 points
Part Number: TLC5940
Other Parts Discussed in Thread: SN74AVC16244

Hi  This is a simple ardunio project with single chip TLC5940 running only 16 red leds.

I followed the tronixstuff tutorial.  I used the library by PaulStoffregen.

I used 2.2Kohm for IREF pin.

What could go wrong? 

I forgot to add ground line to VPRG, leaving it floating. It can't be the reason for this spoilt chip, isn't it?

  • 0
    TI__Genius 14295 points
    Hi, Yap,

    I don't see problem from what you descriped.

    Can you provide your schematic and layout so I can have a quick look?

    Thanks.

    Regards,
    Kenneth
  • 0 in reply to Kenneth Du
    Prodigy 220 points

    Hi Kenneth,

    It is now resolved and working with second chip though the first chip is already dead.

    The problem turns out that the Arduino is powered by USB while the chip is powered with separated 5V power supply.

    Is there a reason why two 5V power supply cannot be used together?

    By the way, on the TLC5940 evaluation board (EVM), what is the purpose of SN74AVC16244? 

    And I read some info that chip cannot be powered on first until the microcontroller is on. Is that true?

    Thank for your help

     Clement Yap

  • 0 in reply to Yap Tsi Searn
    TI__Genius 14295 points
    Hi, Yap,

    It should be OK to use two power supplies.
    SN74AVC16244 is a buffer to condition the input signals to the EVM. This buffer eliminates any noise on the input signals, generates fast, clean rise and fall times, and improves the drive capability of the signal.
    Since the chip need some signals(SCLK, XLAT, GSCLK, BLANK...) which are provided by microcontroller, it cannot be powered correctly until the microcontroller is on.

    Regards,
    Kenneth