LMR14050: LMR14050 SW out put EMI Issue

user3830479

Part Number: LMR14050

Dear TI Team:

Our customer XINGUODU used LMR14050 for 12-24V to 5V/5A application,attached is circuit and waveform.

Issue: SW PIN output integrate 140M-220M noise, EMI test failure. we changed switching frequence , capacitor and layout, but no effect.

Customer project is very urgent ! Do you have any solution for this issue ? thanks!

over 8 years ago

0 Andy Chen over 8 years ago

TI__Mastermind 34875 points

Hi,

EMI testing failed at conduction or radiated band? can you also provide PCB layout for checking?

BTW, the SW node waveform should be measured with shortest proble ground.

0 user3830479 over 8 years ago in reply to Andy Chen

Expert 1090 points

HI Andy:

EMI test failed in radiated band, customer test three times on EMI laboratory. please refer to layout.

0 Andy Chen over 8 years ago in reply to user3830479

TI__Mastermind 34875 points

Hi

The layout looks good.

The switching freq is about 1.2MHz, for high freq high power SMPS, normally it requires metal shielding to pass EMI radiation testing.

can you send me the data sheet of inductor L9? I didn't find it on line. my email add: andy.chen@ti.com

0 Vental Mao over 8 years ago

TI__Expert 5745 points

A little weird waveform of the SW, pls use the DC couple and smallest loop to measure the SW.
Add a snubber circuit (series the R and C to GND) can remove the SW noise.
Also add a R(2ohm~10ohm) in series with the Cboot. But these ways will decrease the efficiency and increase the temp.

As Andy reply , upload your PCB layout.

0 user3830479 over 8 years ago in reply to Vental Mao

Expert 1090 points

Thanks for your support. customer output 5V/2A ,first version used MPS is ok, but change to LMR14050,EMI is very serious. I will sent L9 datasheet and EMI TEST to andy ASAP. could you help check LMR14050 DEMO board test data? if have the same issue? thanks

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LMR14050: LMR14050 SW out put EMI Issue