A few items to consider 1 Core voltage 2 Serdes voltage 3 Internal chip architecture - new chip may have millions more transistors
Higher voltages will result in much higher emi even if rise/fall time is same. ...Marko Sent from my iPhone > On Mar 22, 2014, at 9:03 PM, [email protected] wrote: > > > 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]> - ---------------------------------------------------------------- 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]>
