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TPS563201: is there any requirement for startup

Yuan Tan63
Expert 3280 points
Part Number: TPS563201

Hi,

customer uses this part, and here is the sch as below.

they connect DC supply with VOUT_12 while e-load with VOUT_5.7V. when e-load>500mA, start up DC supply, the output cannot match 5.7V. But when e-load<400mA, start up DC supply, it works well. even change e-load to 1A, the output is stable too.

is there any reason for that?

thank you!

Yuan

  • 0
    TI__Expert 4035 points

    Hi Yuan,

    What's the mean of output cannot match 5.7V? Was the output voltage stable after the soft start?

    There's large capacitance at the output side, when startup with large loading current, it needs huge energy to charge the output cap to 5.7V. Since the TPS563201 has a fixed soft start time of 1ms, after the soft start time, if the real output voltage was still lower than the target, OCP would be triggered. 

    Per your description, i suggest you try without the 470uF E-cap or use a lower value first to double confirm you were facing the above issue.

  • 0 in reply to Ryan Hu (BSR-MV)
    TI__Expert 3280 points

    Hi Ryan,

    Thanks for your reply. but after customer removing the cap, still the same.

    and here is the output waveforms for different loads(300mA, 600mA, 800mA)

    thanks.

    Yuan

  • 0 in reply to Yuan Tan63
    TI__Expert 4035 points

    Hi Yuan,

    I found there is a 100nF cap used for the C82, could you please remove it or instead by a ~100pF cap? 100nF is too large.