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TLC5923: output current drop

Bright Zhu
Intellectual 260 points
Part Number: TLC5923

Dears

Our single board is suitable for 3pcs TLC5923, 4 channels to drive an LED.  

When the dot correction value is set to 380, the channel current is normal. When the dot correction value is set to 385, the current does not rise. When the dot correction value is set to 390, the current rises again. According to our design of Riref = 12K, the value of 5dot should change about 0.16ma. 

Please help to analyze the problem of DOT setting or circuit diagram

The following table is the measured data:

Dot

Iout（mA)

375

14.92

380

15.13

385

15.14

390

15.34

Block diagram

SCH

  • 0
    TI__Genius 12915 points

    HI Bright,

    This is weird that only DC value at 385 have no effect. Is this anomaly happened at all 4 units and all channel? Could you help to retest it again and capture the signal of SIN/SCLK/XLAT/OUT to see if the data is valid and whether outputs changed?

  • 0 in reply to Hardy Wu
    Intellectual 260 points

    Dear Hardy Wu 

    Sorry for later！Thanks for you  reply!

    This is weird that only DC value at 385 have no effect. Is this anomaly happened at all 4 units and all channel?

    It happens in four channels, and the other channels is OK. In addition, from the phenomenon point of view, the problem channel is not the fixed channel of the chip.

     

    Could you help to retest it again and capture the signal of SIN/SCLK/XLAT/OUT to see if the data is valid and whether outputs changed?

    We can add this after retesting. We did the  A-B-A swap test ,The problem following chip  it should not be the problem on the control bus.

  • 0 in reply to Bright Zhu
    TI__Genius 12915 points

    Hi Bright,

    Based on your description, the problem looks like a random issue may due to damage or manufacture defect. What the failure rate? If it is high I think you could contact local sales and request further failure analysis.

  • 0 in reply to Hardy Wu
    Intellectual 260 points

    HI  Hardy

       The SIN / SOUT / SCLK / mode test waveform of abnormal TLC5923 is as follows, which is not abnormal with the normal chip waveform. The waveform can be configured with current valid on the normal chip. Help me analyze it again.

         T

    FA:  Final Report (TNI) as blew

  • 0 in reply to Bright Zhu
    TI__Genius 12915 points

    Hi Bright,

    I do not think it is an application issue. What the failure rate? If it is only a single case, I think it more like a manufacture defect unit. The possible reason may be one bit of DC register is stuck some how.

  • 0 in reply to Hardy Wu
    TI__Prodigy 510 points

    Hi Hardy

    Do we faced this problem in other customers? do you have any suggestion on how to find the root reason of this problem? thank you!

  • 0 in reply to Pei Gong
    TI__Genius 12915 points

    Hi Pei,

    Per talk, I close this thread and we will continually solve this issue offline.