Thanks. Well, the first part will be to check for the corrupted rise/fall time. With such a slow clock – 4.19 MHz – it seems to me the simple solution is if the risetime is sub-ten nanoseconds, to simply slow it down with an RC filter, as opposed to redesigning the board stack-up to provide glitch-free operation.
Agree/disagree? Ken Javor Phone: (256) 650-5261 From: Ken Wyatt <k...@emc-seminars.com> Reply-To: Ken Wyatt <k...@emc-seminars.com> Date: Tue, 26 Jan 2021 11:34:04 -0700 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Digital logic question Hi Ken, The biggest problem I see when faced with RE issues is that clocks, data/address buses and other fast-edged signals do not have an adjacent solid return plane. This is especially important for wireless devices. Have your client check their stack-up, because invariably, you’ll find, if four layers (top to bottom), s-g-p-s, with the power and ground return way too far separated (30 to 40 mils (poor HF decoupling) and with the bottom signal layer referenced to power, instead of the return plane. I discuss this in my four-part article on low EMI design for PC boards: https://www.edn.com/design-pcbs-for-emi-part-1-how-signals-move/ Cheers, Ken _______________________ I'm here to help you succeed! Feel free to call or email with any questions related to EMC or EMI troubleshooting - at no obligation. I'm always happy to help! Kenneth Wyatt Wyatt Technical Services LLC 56 Aspen Dr. Woodland Park, CO 80863 Phone: (719) 310-5418 Web Site <http://www.emc-seminars.com> | Blog <https://design-4-emc.com> The EMC Blog (EDN) <https://www.edn.com/electronics-blogs/4376432/The-EMC-Blog> Subscribe to Newsletter <http://www.emc-seminars.com/Newsletter/Newsletter.html> Connect with me on LinkedIn <https://www.linkedin.com/in/kennethwyatt/> > On Jan 26, 2021, at 10:10 AM, Ken Javor <ken.ja...@emccompliance.com> wrote: > > At my request based on this EMC forum back and forth and the specs on the > processor which is very slow, customer is going to measure clock waveform. > > Ken Javor > Phone: (256) 650-5261 > > > > From: "Grasso, Charles" <charles.gra...@dish.com > <x-msg://20/charles.gra...@dish.com> > > Date: Tue, 26 Jan 2021 16:19:30 +0000 > To: "EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> " > <EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> >, Ken > Javor <ken.ja...@emccompliance.com <x-msg://20/ken.ja...@emccompliance.com> > > Subject: Re: [PSES] Digital logic question > > Agreed. Perhaps your customer could take a measurement on the pwa? > > From: Ken Javor <ken.ja...@emccompliance.com > <x-msg://20/ken.ja...@emccompliance.com> > > Sent: Monday, January 25, 2021 12:07 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: [PSES] Digital logic question > > This message originated outside of DISH and was sent by: > owner-emc-p...@listserv.ieee.org <x-msg://20/owner-emc-p...@listserv.ieee.org> > I’m guessing that, as well. But the entire battery is maybe a foot square and > a half-inch thick, and the board is way smaller than that, which makes me > think super fast risetimes (relative to clock speed), else traces wouldn’t be > long enough to support constructive/destructive interference. > > Ken Javor > Phone: (256) 650-5261 > > > > From: "Grasso, Charles" <charles.gra...@dish.com > <x-msg://20/charles.gra...@dish.com> > > Reply-To: "Grasso, Charles" <charles.gra...@dish.com > <x-msg://20/charles.gra...@dish.com> > > Date: Mon, 25 Jan 2021 19:02:33 +0000 > To: <EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> > > Subject: Re: [PSES] Digital logic question > > Thanks Ken. > > > > Assuming that this is a faithful representation of the signal is ON the > circuit board then there really is a problem > with the clock generation and distribution on the board. My guess is that the > xmission lines are really long and/or > improperly terminated. > > > > To answer your question regarding the "squaring up" of nasty signals. If the > nasty signal is > valid within the operating input switching characteristics of the logic gates, > then the output > will be a cleaned up version of the input (esp at 4MHz). > > > > Chas > > > > From: Ken Javor <ken.ja...@emccompliance.com > <x-msg://20/ken.ja...@emccompliance.com> > > Sent: Monday, January 25, 2021 11:30 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: [PSES] Digital logic question > > This message originated outside of DISH and was sent by: > owner-emc-p...@listserv.ieee.org <x-msg://20/owner-emc-p...@listserv.ieee.org> > This was measured not on the board, but by draping a very short wire over the > equipment plastic case and running that into an o’scope as a troubleshoot. So > this is capacitively coupled to the outside. > > <image.png> > > Ken Javor > Phone: (256) 650-5261 > > > > > From: "Grasso, Charles" <charles.gra...@dish.com > <x-msg://20/charles.gra...@dish.com> > > Date: Mon, 25 Jan 2021 18:21:24 +0000 > To: "EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> " > <EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> >, Ken > Javor <ken.ja...@emccompliance.com <x-msg://20/ken.ja...@emccompliance.com> > > Subject: Re: Digital logic question > > When you say damped sine - does the amplitude decrease with time? (I presume > that the measurement is at the destination). Typically there is too much > series impedance (filtering?) on the signal. > > From: Ken Javor <ken.ja...@emccompliance.com > <x-msg://20/ken.ja...@emccompliance.com> > > Sent: Monday, January 25, 2021 9:28 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG <x-msg://20/EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: [PSES] Digital logic question > > This message originated outside of DISH and was sent by: > owner-emc-p...@listserv.ieee.org <x-msg://20/owner-emc-p...@listserv.ieee.org> > Have a customer who I suspect has way too fast a risetime for his application. > Clock runs at 4 MHz. I’m seeing an ugly damped sine occurring at 2 MHz rate, > leading to broadband outages around 200 MHz. Suspect that a risetime somewhere > is being corrupted. > > Is it enough to slow down the clock’s rise and fall times, or do the logic > chips fed by the clock act as Schmitt triggers and square things up again if > they operate off a fast logic family? > > Thank you, > > Ken Javor > Phone: (256) 650-5261 > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org <x-msg://20/emc-p...@ieee.org> > > > 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 <sdoug...@ieee.org <x-msg://20/sdoug...@ieee.org> > > Mike Cantwell <mcantw...@ieee.org <x-msg://20/mcantw...@ieee.org> > > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org <x-msg://20/j.bac...@ieee.org> > > David Heald <dhe...@gmail.com <x-msg://20/dhe...@gmail.com> > > > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org <x-msg://20/emc-p...@ieee.org> > > > 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 <sdoug...@ieee.org <x-msg://20/sdoug...@ieee.org> > > Mike Cantwell <mcantw...@ieee.org <x-msg://20/mcantw...@ieee.org> > > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org <x-msg://20/j.bac...@ieee.org> > > David Heald <dhe...@gmail.com <x-msg://20/dhe...@gmail.com> > > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org <x-msg://20/emc-p...@ieee.org> > > > 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 <sdoug...@ieee.org <x-msg://20/sdoug...@ieee.org> > > Mike Cantwell <mcantw...@ieee.org <x-msg://20/mcantw...@ieee.org> > > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org <x-msg://20/j.bac...@ieee.org> > > David Heald <dhe...@gmail.com <x-msg://20/dhe...@gmail.com> > > > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org <x-msg://20/emc-p...@ieee.org> > > > 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 <sdoug...@ieee.org <x-msg://20/sdoug...@ieee.org> > > Mike Cantwell <mcantw...@ieee.org <x-msg://20/mcantw...@ieee.org> > > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org <x-msg://20/j.bac...@ieee.org> > > David Heald <dhe...@gmail.com <x-msg://20/dhe...@gmail.com> > > > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org> > > 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 <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
