Hi Ken, Thanks for your response. The rise/fall time in the new ASIC is firmware controlled to match the rise/fall time of the older ASIC. Measurements were made with a 30 GHz bandwidth scope, so I don't think scope bandwidth is limiting the rise/fall time measurement. I agree that flip chip will result in faster rise time, but measurements are being made at the end of the 2" long PCB trace, using SMA connectors.
Regards Ravinder Ajmani HGST, a Western Digital company 5601 Great Oaks Pkwy San Jose, CA 95119-1003 [email protected] Ken Wyatt <[email protected]> 03/22/2014 08:18 PM To "[email protected]" <[email protected]> cc "[email protected]" <[email protected]> Subject Re: [PSES] Higher EMI from ASIC built with new process It could be your scope doesn't really show the true rise time of the faster chip. I suspect the flip chip really does have faster rise times. Kenneth Wyatt Wyatt Technical Services LLC Woodland Park, CO [email protected] www.emc-seminars.com (Sent from my iPad) On Mar 22, 2014, at 8:38 PM, [email protected] wrote: Hi Experts, I am comparing EMI from two ASICs. Both have identical rise/fall times and signal amplitude. Yet the ASIC built with the later technology not only has significantly higher radiated emissions, but also shows much broader noise spectrum. PCB stackup and layout is identical. Please help me understand what other factors can be responsible for this anomaly. The older ASIC uses a wirebond package, whereas the new ASIC has flip chip package. Regards Ravinder Ajmani HGST, a Western Digital company 5601 Great Oaks Pkwy San Jose, CA 95119-1003 [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]> - ---------------------------------------------------------------- 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]>
