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TLC59281: Wrong data on SOUT

Nigel Meijer
Prodigy 20 points
Part Number: TLC59281

I've been trying to drive a few of the TLC59281
But it is a mistery why it wont latch the right data to SOUT

Aditional info:
OUT0 - 15 Connected to 16 leds.
VDD:   external 3.3V
SIN:    SPI on 2,5MHZ driven by a stm32f4 discovery board.
IREF:  2.2K
Blank: pulled to GND
Latch is 100ns after the last falling edge of the clock.

The strange part is, when i latch a few bytes into the TLC59281 for example.   "0x01, 0x02" The leds on those pins turns on, if i then latch "0x03, 0x04" into the chip i expect the first two bytes on the SOUT.
Tried multiple chips but same behaviour.

Added some scope/analyzer images to show my output.

Top to bottom: CLK, SIN, SOUT, Latch

Same as first image but zoomed in part 1.

Same as first image but zoomed in part 2

So i wonder if I'm missing something.
Thank you in advance for any reply's

  • 0
    TI__Expert 3190 points

    Hi Meijer，

    you are right, it is the mechanism the device works.

    The shift register will be reset to reserved register value after the LATCH rising edge comes. So what you see about the SOUT is actually the reserved data. Page 14 in the datasheet gives a detail description, you can refer to that content.

    Also I suggest set the BLANK high at the beginning, and then set it to high when you want to turn on the channels.  

    Regards!

    Shawn.

  • 0 in reply to Shawn Ding
    Prodigy 20 points
    Hi Shawn,

    Thank you for your reply!
    This resolved my issue.

    Regards,