EMI Radiated Emission Problems MIE1W0505BGLVH

DC-DC Power Converters
1

Hi

I have high radiated EMI Problems over the hole 30MHz to 1GHz spectrum. I use the MIE1W0505BGLVH for an isolated RS485. The DC/DC Converter is pretty close to the edge of the PC Board.

I attached the EMI-Measurement, Layout and Schematic.

I made some measurements with a near field probe just around the MIE1W0505BGLVH. So I was able to confirm that a big part of the problematic emission spectrum is from the DC/DC Converter.

Any help how I could improve my isolated RS485 is very welcome.

Cédric

Schematic-MPS-EMI
Schematic-MPS-EMI1502×883 91.7 KB

Layout-EMI
Layout-EMI1240×1753 155 KB

EMI-Problem-T2796 EM RE 30M1000M AC-2-1
EMI-Problem-T2796 EM RE 30M1000M AC-2-11754×1239 134 KB

2

Hello,

Your schematic looks like it matches the datasheet. See the following layout guidelines attached:

image
image549×881 125 KB

Perhaps it would benefit you to add a Y-Cap in order to bypass EMI noise.

3

Please see the following figures for further reference:

image
image454×1107 70.7 KB

Keep us updated given further testing here.

Best,

Krishan

4

Hi Krishan

Thank you for your support.

I will add Y-Cap and if possible other additional filter components and measure again the radiated emission.

Thank you so far for your help

5

No problem, keep me updated on the results after adding a Y-cap to the system.

Just as a note, the voltage rating of the Y-capacitor must be equal to the insulation voltage of the internal transformer, which is equivalent to the maximum voltage threshold of the MIE1W0505BGLVH. Sizing the voltage with headroom is my personal recommendation.

Also, be sure to use an SMD package with a low ESL.