• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 61 subscribers
  • Views 458 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLC5951 Questions.

Richard Elmquist
Mastermind 45250 points
Other Parts Discussed in Thread: TLC5951

I have a customer asking the following questions regarding the TLC5951:

The micro is using 3 independent timers as a PWM signal, all running at 31kHz to drive the GSCLK(RGB) inputs. Albeit, same all 3 timers have the same PWM frequency, each GSCLK is not fully aligned with the other in hopes to reduce emissions from the board. During GS data transfer, XBLNK is held high, GSLAT is cleared, data is sent, and then GSLAT is pulsed high then low. Are GSCLK supposed to clocking all at the same time? If what we're doing is ok, what is the draw back?

They are also experiencing “ghosting” on the outputs. Here are their questions concerning this:

We have noticed that there seems to be a significant 'off' time (in the ms) at the input our RGB LEDs if we do not continually push new GS data into the driver even though the 'auto repeat' option should take care of that... In that case, what is the correct implementation if this is not the desired behavior??? If we do not continually push new GS data into the driver, we end up with a Ghosting effect due to the LED's not being on at 100% duty (hence the ghosting I was talking about). Would the same time/ same frequency but different duty cycle help alleviate the problems we're seeing? Any thoughts on how to alleviate these issues would be much appreciated.

Please let me know if you have any further questions for the customer.

Thanks for your help with this!

Richard Elmquist

  • 0
    TI__Mastermind 45250 points

    Has anyone had a chance to look at the request above?

    Can you give a time frame as to when you might be able to provide the information?

    Thanks for your help with this!

    Richard Elmquist

  • 0
    TI__Expert 4035 points

    Hi Richard,

    GS data should only be latched into the GS data latch at the end of a display period when XBLNK is low, otherwise latching GS data could cause the outputs to turn on or off unexpectedly. GSCLK still clocking or not, which is not mandatory because the falling edge of XBLNK resets the three GS counter values to '0'. And the GS counter values are held at '0' during XBLNK is low, even if the GS clock input is toggled high and low. And I don’t know what the meaning of “what is the draw back?”

    Refer to the Ghosting effect, I’m not sure about the reason, but using three different GSCKR/G/B is supported that should not be the main reason. Maybe you should latch GS data on condition that mentioned as above first, and then to see if it could be solved.

    BRs,

    Ryan

  • 0 in reply to Ryan Hu (BSR-MV)
    TI__Mastermind 45250 points

    Ryan,

    Thanks for your response!

    I will let you know if the customer has any further questions.

    Thanks again.

    Richard Elmquist