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Original question:

TPS2663: Parallel connection possibility for spreading thermal

TPS2663: two devices parallel gives "oscilation" during startup with big capacitive load

Rob Hoeks
Prodigy 90 points
Part Number: TPS2663

Hei,

I have two TPS26630 in parallel and this works fine for resistive or small capacitive loads. Bu if i have a bigger capacitive load(5mF for example) the startup behavior to me is a bit weird. 

The schematic is attached below.

In the Oscilloscope picture the startup behavior is visible.

Ch1, Yellow, is Vout

Ch2, green, is Imon of one of the 2 tps26630

Ch3, blue , not attached

Ch4, Red, Pgood signal

It's great that it starts up, but i'm not sure the startup is ok...

Can you advice me in this?

  • 0
    TI__Guru** 105361 points

    Hi Rob,

    Thanks for reaching out.

    It is the expected behavior. Due to large capacitive load, the device goes into current limit mode of operation and then gets into thermal shutdown. Can you increase capacitor at DVDT pins to 1.5uF to set lower inrush current so that the power stress across the device will be low to avoid thermal shutdown.

    Another approach is to force the device into thermal regulation loop with Cdvdt = OPEN similar to Figure 22 in the datasheet.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    TI__Guru** 105361 points

    Hi Rob,

    Did you get chance to test with the above suggested changes ?

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 90 points

    Hi Rakesh,

    Yes, i managed to test and it works great. We need to investigate a bit more to find our ideal settings. Those big capacitive loads are not standard and we don't want a startup time which is that long.

    But, your answer did help us a lot to get to the cause of the issue, so thank you!

    Best regards,

    Rob

  • 0 in reply to Rob Hoeks
    TI__Guru** 105361 points

    Hi Rob,

    Good to know that.

    Please close this thread if you don't have further questions.

    Best Regards, Rakesh