TPS562200: Need Support for RE test issue resolution

HI

the radiation source coming from the switching behavior of dcdc , which have high dv/dt and di/dt. Can you help

1. adding snubber to reduce the di/dt or dv/dt of switching node, you can try 100pF and 2.2ohm first to see any improve

2. not sure whether the inductor is shielded, if not, can you try the shielded inductor?

Thanks

Daniel Li

Hi Daniel,

Thank you so much for answering here.

1. adding snubber to reduce the di/dt or dv/dt of switching node, you can try 100pF and 2.2ohm first to see any improve.

BK - We have added suggested snubber values but we do not see any much improvements, results remains same only. Below are results.

2. not sure whether the inductor is shielded, if not, can you try the shielded inductor?

BK - We are using shielded inductor only. 

Can you please suggest further steps to solve this?

Hi 

Can  you compare the SW(500Mhz bandwidth) original dv/dt with adding snubber to see any SW slew rate change? if not obvious change, you can increase 100pF to 470pF to see any improvement 

by the way, do you have layout for refer?

Thanks

Hi Daniel,

We have done comparison and  i am sharing for your check. Layout view also has been added in the same file.  Here I have attached XLS file in which results are added.

RE Rework.xlsx

Hi:

Thank you for your sharing, 

layout looks fine to me.   pls try 470pF 2.2ohm or 470pF 5.1ohm .

Thanks

Hi Daniel,

Sure we can try and check.

one thing I want to understand here why it radiates at 36-37 MHz frequency because its switching frequency is at 750 KHz around? There is so huge difference between these frequencies? 

Thank you

Brijesh K

Hi Daniel,

We have done suggested testing please look in attached xls file.

one thing I want to understand here why it radiates at 36-37 MHz frequency because its switching frequency is at 750 KHz around? There is so huge difference between these frequencies? 

RE Rework_6JAN25.xlsx

HI

As the dv/dt and di/dt of dcdc which is the raising edge and falling edge of SW is key noise of high frequency noise, that's why I want to add snubber to change the SW raising edge or fall edge frequency to reduce the high frequency noise.

but it looks like the noise coming from the resonation of the below waveform, Can you help share which node you test on?

Thanks

Daniel Li