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LP5036EVM: LP5036EVM with RED LED stuck on/no longer able to talk to chip.

user6417729
Prodigy 30 points
Part Number: LP5036EVM
Other Parts Discussed in Thread: LP5036,

Recently designed in the LP5036 into a product we are developing.  We bought the LP5036EVM module to interface to an external set of LED's that we want to use in a specific pattern. 

All we have is a board with a set of RGB leds that are common anode. The cathode of each LED is fed to the EVAL board using a 8 inch ribbon cable.  3.6V is applied to Anode of LED and to the EVAL PCB to keep consistency. They seem to work for some time.  After a few hours of making different patterns and checking current draws the Red LED's on all channels are staying on.  They do not seem to be fully on but almost like the driver of the RED LED is leaking current.  This has happened now on 3 devices.

I have 2 LP5026EVM units now that have the RED LED.  I have one unit that will not even talk to the USB any anymore.  These devices/EVAL seem very susceptible. I am unsure is ESD has damaged the IC as the Eval board has no protection that I can see. Using the gui I know I am not over currenting the device.  Any info of what may be happening?  I have a tech support request in to repair or replace the devices but needed to post in the forums for feedback first.

  • 0
    TI__Expert 8565 points

    Hi,

    I have some details which need to confirm with you:

    'They do not seem to be fully on but almost like the driver of the RED LED is leaking current'

    do you mean the current will decrease after several working hours? what about your PWM configuration and could you please provide some picture for understanding? 

    Best Regard

    Monet Xu

  • 0 in reply to Monet Xu
    Prodigy 30 points

    With the GUI of the LP5036 EVM set to 0% brightness the RED LED is still on but at a reduced current consumption.  If I put it to 100% brightness it gets brighter and the LED draws more current.   It seems the Red LED driver is damaged.  And it has happened on a few units we have on the EVAL PCB.  

  • 0 in reply to user6417729
    TI__Expert 8565 points

    Hi user,

    We didn't meet this problem before. Could you have the following trying?

    Please read all registers after set 0% brightness and set 100% brightness, and show me the two pic of result. Test SDA and SCL waveform when write 50% to LED0_brightness. If you can provide the schematic diagram and PCB, it will help a lot. 

    Best Regard

    Monet Xu

  • 0 in reply to Monet Xu
    Prodigy 30 points

    Hi Monet,

    I will try to get this info in near future.  I am presently working on other issues at the moment.  One thing to note.  Even with the USB to ANY disconnected and power applied to the LP5036EVM PCB the RED LED is still on.  So even without any communication to the device the LED is on.

    Regards,

    Adam

  • 0 in reply to user6417729
    TI__Expert 8565 points

    Hi Adam,

    When power on, the default register will keep the LED off and theoretically the red led should not be on. I suppose that there may be some hardware problem. Please provide the Circuit board physical picture and I will help to check it,

    I will close the problem first and when you are free, please replay under the question and I will support you again~

    Best Regard

    Monet Xu