TPS54229 startup issue

Moon Li，

  It's weird. There should be no problem on the EVM board. What's your power source? Would you do a test again?

and capture the input voltage and output voltage on the same time with ossilloscope. To make sure whether the power source affect the DC/DC.

最好分享一下原理图，请Check输入是否有高频的滤波电容，验证下SS 脚位是否异常

Are you using E-load? please check the threshold setting. Or you try to re-test with a pure resistor as load.

We using two type E-Load, One is Chroma,another is  ITECH,  increase the inductor would optimize the ripple voltage when using Chroma;but no obvious improvement when using ITECH, You mentioed check the thresold,how to set ? Thanks! BTW we did the test using TPS54229 EVM..input voltage is normal.

the threshold makes load active called Von, you can refer the handbook for setting.  usually there is a current spike when E-load active(  may see 3A peak for 1A CC setting, depends on which type load used), you can check the start up waveform and track the load current using current probe.

Thanks stone, the default ON and off threshold are both 0v, we set ON=0.1v, and OFF=0.05v,no spike voltage emerge during startup; 1. but use MP1482 has no that issue-(no need to set the threshold ) ; 2. another issue is when shutdown the power, the ouput voltage has undershoot when use ITECH E-load, no undershoot when use Chroma E-load, we are confused about that,because we need pass test in both two E-load before change to TPS54229 ? Anyone can help clarify, thanks!