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TLC5923: output current drop

Ben Kuo
Expert 7135 points
Part Number: TLC5923

Dear expert,

We have designed TLC5923 and face an output current drop issue now.

one of channel o/p current will drop around 90uA when turn off other channel output(total o/p current is around 200mA).

For example, CH#1 output 5mA; CH#2,3,4 total output current is 210mA. After shutdown CH#2,3,4, CH#1 will drop 90uA.

May I know why? And how to solve this issue?

Thanks!

-Ben

  • 0
    TI__Expert 3190 points
    Hi Ben,

    Do you mean the CH#1 is separated, and CH#2,#3,#4 are connected together?

    If so, It should be the reason that the supply voltage has been changed when the CH#2,#3,#4 shutdown. Could you help to test the transient voltage of the supply power?

    If not this reason, please let me know, thanks!
  • 0 in reply to Shawn Ding
    TI__Expert 7135 points

    Hi Shawn,

    All LEDs on each channels are separated, but connect to the same power source.

    We will test voltage transient and see if it is the root or not, thanks!

    Ben

  • 0 in reply to Ben Kuo
    TI__Expert 7135 points
    Hi Shawn,


    There are no transient voltage after we turn on/off LED.
    May I know which item I should check first about this issue?
    Thanks!

    -Ben
  • 0 in reply to Ben Kuo
    TI__Expert 3190 points
    Hi Ben,

    If it is not the supply power, it should be the ground problem. Since the ground is not the ideal, there are resistance between the device ground to earth ground, and also each channels ground also different and have the different resistance to the device ground. These resistance cause the channel current deviation when channel current changes.

    Can you help to check the PCB layout to see if it is the ground problem? Also, please help to test if turn off CH1,2,3/1,2,4/1,3,4 and see the current of CH4/CH3/CH2.

    thanks!
    Best regard!
  • 0 in reply to Shawn Ding
    TI__Expert 3190 points
    Hi Ben,

    I will close the state of this question thread, If you have any feedback, just reply, it will open again.

    thanks!

    Shawn.