🚀 go-pugleaf

On Jan 12, 2:56 am, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
> On 01/11/2012 07:49 PM,BillSlomanwrote:
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> > On Jan 11, 8:22 pm, Phil Hobbs
> > <pcdhSpamMeSensel...@electrooptical.net>  wrote:
> >> On 01/11/2012 01:43 PM, John Larkin wrote:
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> >>> On Tue, 10 Jan 2012 18:02:50 -0800 (PST),BillSloman
> >>> <bill.slo...@gmail.com>    wrote:
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> >>>> On Jan 10, 4:55 pm, John Devereux<j...@devereux.me.uk>    wrote:
> >>>>> Robert Macy<robert.a.m...@gmail.com>    writes:
> >>>>>> On Jan 10, 2:28 am,BillSloman<bill.slo...@ieee.org>    wrote:
> >>>>>>> On Jan 10, 7:47 am, "David L. Jones"<altz...@gmail.com>    wrote:
>
> >>>>>>>> Just thought some might be interested in hearing our recent guest on
> >>>>>>>> our Amp Hour radio show, Dr Howard Johnson of "Handbook of Black
> >>>>>>>> Magic" fame:http://www.theamphour.com/2012/01/10/the-amp-hour-77-winsome-waveform...
>
> >>>>>>>> Lots of history of the book, signal integrity, Gigabit Ethernet
> >>>>>>>> development, 90 degree PCB bends, audiophoolery, and a whole bunch of
> >>>>>>>> other talk over almost 1 1/12 hours.
>
> >>>>>>> "Black Magic" is more notorious than famous. I own both it and it's
> >>>>>>> follow-up, and both have got some useful content but they are badly
> >>>>>>> organised and what useful content they do contain is hard to find.
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> >>>>>>> The field is still waiting for a decent textbook on high speed circuit
> >>>>>>> design and layout.
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> >>>>>>> This is one of the few matters on which John Larkin and I seem to
> >>>>>>> agree.
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> >>>>>> Perhaps, it is time for the first ever 'conference' book written by a
> >>>>>> consortium of engineers/scientists.
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> >>>>>> Put my name in for proffreading.  :)
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> >>>>> Great idea. Perhaps John Larkin, Jim Thompson andBillSlomancould
> >>>>> collaborate on it.
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> >>>>> Sure that will work out well... :)
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> >>>> I'm not sure what Jim Thompson might contribute. I've seen papers that
> >>>> worry about the characteristic impedance of connections on the silicon
> >>>> (or whatever) inside integrated circuits, but I don't have the feeling
> >>>> that Jim designs stuff that's big enough and fast enough for him to
> >>>> need to know much about it.
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> >>> I get the impression that most interconnects inside ICs are primarily
> >>> distributed R-C things, not real transmission lines at all.
> >>> Propagation speed of interconnects is a big deal in routing fast logic
> >>> chips, but the speed of light isn't the issue.
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> >>>> Motorola's ECL applications notes on board layout were rather useful,
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> >>> Just don't trust their microstrip equation!
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> > They looked okay in the range 50R to 75R. Specialised textbooks give
> > longer and more complicated expressions that give rather different
> > results for microstrips and strip-line with higher and lower
> > characteristic impedances.
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> >> Yup, all RC transmission lines with repeaters, speed roughly c/10.
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> > I wonder what Dr. Hobbs thinks he is talking about - the Motorola  ECL
> > application notes discussed proper microstrip and stripline
> > transmission lines, where the propagation delay is basically that of
> > electromagenetic waves in dielectric - something around two-thirds of
> > the speed of light in vacuum (depending on the dielectric constant of
> > the substrate).
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> On-chip interconnects, even the fatwire levels, are all RC.  Once you
> get off the chip, you have to worry about transmission line effects, but
> the losses in chip wiring are so horrendous that you have to use
> multiple repeaters to go a couple of centimters. The delays in the
> repeaters, and the edge degradation due to RC rolloff, produce a net
> propagation speed of about c/10.  Of course my information is two or
> three years old at this point, but I wouldn't expect inductance to get
> more important anytime soon.

It's an entirely valid point, but you inserted the comment a couple of
paragraphs further down the post than you should have - it looked as
if you were commenting on the limitations of the Motorola ECL
application notes (which were perfectly okay, though they should have
included a caution about the range of validity of the trace-impedance
expressions) rather than on the sort of experience Jim Thompson might
have had in laying out transmission lines (very little to none).

--
Bill Sloman, Nijmegen