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TPS61181A: Two in Parallel Turn off after half a Second then heat up

Felix Roch
Prodigy 90 points
Part Number: TPS61181A

Hello,

I'm trying to use two TPS61181A to drive one LP097QX1 Display. (12 Strings)

LED-Anode 1 and 2 are presumably connected in the Display Unit.

The Problem I'm facing is that the Lighting works for about 1/2 to 1 Second before turning off.
After turning off, the two Units heat up rapidly.

This happens when Powercycling the Device as well as when disableing, then reenabling them using the EN Pin.

Can somebody explain to me why this is happening and how to fix it?

  • 0
    Prodigy 90 points
    This doesn't happen without the Display-Cable Plugged in.
  • 0 in reply to Felix Roch
    TI__Expert 4550 points
    Hi Felix,
    We don't recommend to use two chips together like this, because these two units are trying to control the same output voltage.
    You said "the Lighting works for about 1/2 to 1 Second before turning off", does the device turning off by EN? or Vin? or the device turns off by fault condition?
    what does the Display-Cable refer to? it connects the LEDs ?
  • 0 in reply to Caryss Li
    Prodigy 90 points

    Sadly I don't have a way to measure the Output of the Fault Pin.

    EN stays high, so I can only assume there is another Reason for the ICs to turn off the LEDs.
    What would be the behaviour if the Input Voltage Drops due to excess Amouts of Current being drawn?

    In this case the Display-Cable connects the LED Lines as well as the Data Connections for the Video Signal.

  • 0 in reply to Felix Roch
    Prodigy 90 points

    After Desoldering L1, the Device runs without turning off.
    EDIT:However, half of the Backlight Strings don't light up, leading me to believe that the Anodes are split as the Datasheet Suggests.

    Even with one TPS61181A effectively disabled, the active one gets hot to the touch over time, leading me to believe that there is a Thermal management Issue involved.
    However, I don't think this is the root of the Issue, since when both ICs are running they get hot enough to vaporize what little Flux remains on the Board in a matter of Seconds.

    I doubt that a Groundplane of any size could sink that amount of heat in such short time.

  • 0 in reply to Felix Roch
    TI__Expert 4550 points
    Hi Felix,
    The power loss on the chip mainly comes from supply current*Vdd, MOSFET power loss and current sink powerloss. if you could estimate the power loss on chip and use the thermal metric table in datasheet, you could get the temperature rising of the chip.