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TLC59116: "blip on dimming cycle of TLC59116

Steve Chaplin
Prodigy 30 points
Part Number: TLC59116

We are successfully using this device (TLC59116IPW) in an LED fixture, but there is what appears to be a random "blip" when reducing the duty cycle of the PWM, there is occasionally 1 or multiple channels at different times that go "bright" for a fraction of a second then return to the dimming cycle.

The rate of dimming is constant each time but the channel that "blips" is not consistent, different channel and varying point of dimming.

We have recorded the I2C data to check if there may be a glitch there and none is apparent.

The cycle from dim to bright has no issues, only bright to dim.

Any ideas please?

  • 0
    TI__Genius 14295 points
    Hi, Steven,

    How do you realize the bright to dimm cycle?

    Do you use GRPPWM?

    Thanks.
    Regards,
    Kenneth
  • 0 in reply to Kenneth Du
    Prodigy 30 points

    Hi Kenneth,

    We use the Group Dim (GPPPWM) to change the dim level. All our writes in the testing are sent to ALL devices at the same time using the ALLCALL address. 

    We have tried an automatic dim rate where we transmit a timed step change to the TLC59116 (steady rate of change). During these tests, we have monitored the I2C bus transactions to make sure that we are sending the correct data and that the data is not being corrupted. 

    There is never a issue with ramping up the light output, only during the ramp down. The flash we see is not consistent and does not occur on all TLC59116 devices at the same time. Our configurations have between 2 and 12 TLC59116 chips connected on the same bus, and the flash occurs in all of the configurations. 

    The flicker appears as a bright flash, well above the currently selected output level, and normally in the lower half of the dim range. That said, we have also observed the flash in the upper half on the odd occasion.

    Any input welcome.

    Cheers

  • 0 in reply to Steve Chaplin
    TI__Genius 14295 points

    Hi, Steven,

    Can you help to use refreshing each channel PWM to achieve the dimming and refer to the following code:

    TLC59116 Sample Code.zip

    It should solve your problem.

    Please help to click "Resolve" if the problem is solved.

    Thanks.

    Regards,

    Kenneth

  • 0 in reply to Kenneth Du
    Prodigy 30 points

    Hi Kenneth,

    Thank you for your suggestion, unfortunately this method of individual PWM control will not work for us as it will reduce our dynamic dimming range.

    Our application has the various channels set to different levels in order to obtain a specific rendering, at that point we need to group control PWM so that the relative intensity between each channel remains the same as we dim the output.

    The issue is only when ramping down, not ramping up.

    Thank you 

    Regards

    Steven