Hello Amund – If adding a CMC only “seems” to make a difference then I suggest you look harder for the cause.
Adding the resistors will lower the signal levels which can reduce the emissions. So I suggest you measure the eye ASAP. In general, resistors in signals are better than ferrite beads for signal quality. Best Regards Charles Grasso Compliance Engineer Echostar Communications (w) 303-706-5467 (c) 303-204-2974 (t) [email protected]<mailto:[email protected]> (e) [email protected]<mailto:[email protected]> (e2) [email protected]<mailto:[email protected]> From: Amund Westin [mailto:[email protected]] Sent: Friday, February 05, 2016 1:38 AM To: [email protected] Subject: [PSES] Ferrite bead vs. resistor Had some EMI issues, caused by a LVDS line. By inserting CM chokes, the radiation seemed to lower significant. Inserting resistors as well (aprox 22 ohm) made it even better. I can’t check the eye curve, but 22ohm makes no problem with the EUT operation. But, should the series resistor be replaced by ferrite beads instead? Will it make any really differences? The LVDS clock is approx 40MHz and data rate 160Mbps. #Amund - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
