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TPS25947: TPS259474A protection issue

Bryan Chang
Prodigy 50 points
Part Number: TPS25947

Tool/software:

Hi Ti support team Members, 

When PD Adapter plug in ( TBTA_VBUS2/ 20V) , TPS259474A output pin 6 voltage is abnormal keeping on and off about 5 cycles  (showing as below  Chanel 4 waveform) 

Could you figure it out what is happened ; what kinds of protection is triggering ? 

C1 EN PIN

C2 current

C3 VIN

C4 Vout

Thanks a lot 

BR

Bryan 

  • 0
    TI__Mastermind 39045 points

    Hi Bryan,

    This looks like TSD happening during startup and then after 110ms delay, auto-retry of device trying startup again. During each startup, the output caps charge until eventually inrush current reduces enough to not cause TSD during startup.

    Increasing the DVDT cap to slow down the startup (reducing the inrush current) should resolve this issue.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 50 points

    Hi Arush,

    Thanks a lot  for your solution.  

    I try to put a  DVDT cap from 1000pF to 8200PF , it is until 8200pF to fix this problem 

    Output rising time (0V~20V)  is about 70ms 

    M/B total Cout is about 1130UF 

    Is that OK to put  8200PF for this design ( Is it need to add a 100-Ω resistor in series with the capacitor on the dVdt pin, 

    although it is < 10nF? )

     

    By the way I try to calculate the Iinrush is about 0.275mA ( Cout is about 1130UF)  is that correct? 


    Thanks a lot for your soon response 

    BR

    Bryan 

  • +1 in reply to Bryan Chang
    TI__Mastermind 39045 points
    Bryan Chang said:

    Is that OK to put  8200PF for this design ( Is it need to add a 100-Ω resistor in series with the capacitor on the dVdt pin, 

    although it is < 10nF? )

    resistor shouldn't be required as it is within the limit. 

    Calculation looks good. We have a design calculator. You can also use that for calculations. https://www.ti.com/tool/download/SLVRBH5

    Best Regards,
    Arush