ADP5071 EMI suppression in Radiative Emission certification test

pedrocorreia on Jan 30, 2019

Hello

I've recently developed a power board for a frontend data acquisition system, in which I've the ADP5071 to provide the +/-5V for opamp circuitry.

I've used the recommended schematics and board layout described in the datasheet, however during the certification process it was identified high values of radiative emission with a fixed frequency ~2.4Mhz. Any hints how to fix this?

Thank you in advance

Top Replies

Fil
Feb 4, 2019 +2 suggested
Please consider doing 1.2MHz switching frequency and see if there is improvement. Also, consider putting SLEW pin to AGND as this will help for best noise performance.

0 Fil

on Feb 4, 2019 7:12 AM
Please consider doing 1.2MHz switching frequency and see if there is improvement. Also, consider putting SLEW pin to AGND as this will help for best noise performance.
Cancel
Up +2 Down

Reply

Verify Answer

Reject Answer

Cancel
0 pedrocorreia on Feb 4, 2019 12:16 PM in reply to Fil

I've tried, it considerably reduced the noise levels (I've used an oscilloscope probe around the inductor case to measure it). Nevertheless, the noise level has to be reduced around 15 dB, I've reduced the signal amplitude to about half of the original amplitude, and with lower oscillating frequency, but I don't know if this is enough to reduce the overall levels 15dB.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 Fil

on Feb 11, 2019 7:38 AM in reply to pedrocorreia
A second stage filter will help. You may read this article.

https://www.analog.com/en/technical-articles/designing-second-stage-output-filters-for-switching-power-supplies.html

Second stage filter is supported by ADIsimpower excel tool that can be downloaded in ADP5071 product page.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel