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TPS65130: the overshoot of VSN under dynamic load

Jay Li
Prodigy 100 points
Part Number: TPS65130

Hello ,

In our application , the VSP and VSN of TPS65130 is connected to a dynamic load under 90HZ.(the TE signal represents the dynamic frequency of the load)

After we disable power-save mode , the overshot of VSP is small , but the overshot of VSN is still very large.

How can be improved this overshot of VSN ?

Below is our schematic and test waveform:

  • 0
    TI__Mastermind 23560 points

    Hi Jay,

    Theoretically the forward capacitor and CN capacitor can help to improve the transient response.

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Prodigy 100 points

    Hi Patrick ,

    Which is the forward capacitor ?

    Today I did the following tests:

    First , I added the output capacitor to 66uF , it has liitle effect on the overshoot of VSN .

    Second , I reduced the CN capacitor and found that the overshoot of VSN improved significantly after removing this capacitor.

                 So whether this capcitor can be removed ?

    Third , I added the feedback capacitor (C18) to 12pf+10k in series , it has liitle effect on the overshoot of VSN .

    BR 

    Jay

  • 0 in reply to Jay Li
    TI__Mastermind 23560 points

    Hi Jay,

    CN capacitor is related to the loop compensation so it is not recommended to remove it.

    May I know whether this overshoot will cause any risk? I attached a document which will help you design the feedforward capacitor.

    slva289b

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Prodigy 100 points

    the voltage range of VSN is from 5.6V to 5.8V in our customer ERS.

    But the test result currently is out of this range . 

    I have repeatedly verified that only by removing the CN capacitor can we get colse to the required range.See the following test waveform:

    So I would like to ask from the chip spec , what is the evaluation standard of this overshoot ?

  • 0 in reply to Jay Li
    TI__Mastermind 23560 points

    Hi Jay,

    You can refer to Figure 8.41 to Figure 8.44 in our datasheet for the transient response we have tested. As for CN capacitor, it is related to loop stability so it is not recommended to remove it. 

    BR

    Patrick