TPS54202: Pulse skip mode SW waveform

Hi Dino,

Seems chip is not stable , could you help share the sch and layout for review ?

BRs,

Young

Hi Young, 

Please refer to the attached. 

18V system? or 14V system?, this waveform is from same schematic and board just difference is input voltage. 

 TPS54202 schematic and layout_E2E.pptx

Thank you. 

Hi Dino,

The LC is too large for me, could you try to replace 15uH inductor with larger Isat/Idc and 4-5 X10uF cap to see if any improvement ？

BRS,

Young

Hi Young, 

Do you mean there's something wrong with both 18V and 14V input system? 

Under load condition, there is no abnormal output. What kind of problem can this waveform cause? Please let me know your opinion. 

Thank you.  

Hi Dino,

It seems device is not stable at light condition for both power rails . 

You may need re-configure the inductor and output cap . And you can check with WEBENCH tool online Power Designer (ti.com)

BRs,

Young

Hi Young, 

Thank you for your quick response. 

I will try it again as your commendation and I will touch you again. 

Thank you. 

Hi Dino,

sure , no problem. Pls let us know if there is any concern.

BRs,

Young

Hi Young, 

Attached waveform is for TPS54202 EVM, under 14V input / 12V output condition 

Please review it and let me know your opinion EVM waveform is stable or not. 

SW waveform per input and load_E2E_211209.pptx

Thank you. 

Hi Dino,

for LG board waveform, the waveform seems strange to me as the Voltage is not 0 when LS on at light load .

For the EVM waveform, what's the sch and 0ma/5ms and 10mA/50us meaning ? , Pls reach out to young-zhao@ti.com, we can talk directly to solve this issue.

BRs,

Young

Hi Young, 

Thank you for your reply. I sent mail directly.