Sometimes we have just one low inductance supply (usually ground) and if
we had enough capacitance on-chip then we can still run high data
rates with a poor power return for outputs that are CMOS that use
both pull-up and pull-down such as CMOS full-swing and LVTTL. So
in some cases it is a 'limited benefit' but in others it is not.
> IMHO the best bet for minimizing SSO transients is to use balanced codes
> such as 8b/10b so that there isn't any substantial common-mode current.
> Actually saves pins and cuts jitter too.
Not sure where you are coming from here. 8b/10b will work if you
have a DC block in your system. But for SSO transients you've got
to get current supplied during the switching event - not just average
out the current demand over 10 bits.
Can the confusion be that you have a single rail output driver, such
as GTL, in mind whereas many of us are thinking more of a two-rail
output driver such as LVTTL or full-swing CMOS?
> > -----Original Message-----
> > From: D. C. Sessions [mailto:email@example.com]
> > Sent: Monday, September 20, 1999 9:08 AM
> > To: firstname.lastname@example.org
> > Subject: Re: [SI-LIST] : RE: Another decoupling question
> > "Volk, Andrew M" wrote:
> > >
> > > Chris -
> > >
> > > I agree the best capacitance is on-die. It is expensive in die area, but
> > > becoming more and more essential as edge rates and speeds increase.
> > > However, there exist devices already without such provisions and I was
> > still
> > > wondering whether capacitors can be placed under BGA packages to help
> > > existing power decoupling problems. Is it cost effective and
> > > manufacturable?
> > > -----Original Message-----
> > > From: Chris Cheng [mailto:email@example.com]
> > > Sent: Friday, September 17, 1999 1:52 PM
> > > To: firstname.lastname@example.org
> > > Subject: RE: [SI-LIST] : RE: Another decoupling question
> > >
> > > for ~10nf, you are better of putting it insider the die. (yes, on
> > > die decouping)
> > > chris
> D. C. Sessions
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>-- End of excerpt from D. C. Sessions
-- _______________________________________________________________ Mike Degerstrom Email: firstname.lastname@example.org Mayo Clinic 200 1st Street SW Gugg. Bldg. RM 1042A Phone: (507) 284-3292 Rochester, MN 55905 FAX: (507) 284-9171 WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html _______________________________________________________________
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