Hi, I concur with you. Increased capacitive load reduce the slew rate on the driver outputs. The slower the output slew rate, the lower the ground bounce will be. Edi =20 > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] > On Behalf Of Hal Murray > Sent: Tuesday, March 14, 2006 12:26 PM > To: si-list@xxxxxxxxxxxxx > Cc: hmurray@xxxxxxxxxxxxxxx > Subject: [SI-LIST] Ground bounce (was VOH datasheet question) >=20 >=20 > > You could clarify this issue from Dr. Johnson article named "Big > > Buffer" (http://www.sigcon.com/Pubs/news/8_07.htm). >=20 > As usual, his stuff is very good reading. >=20 > This paragraph caught my attention. >=20 > > The main factors that affect SSO noise are (1) the aggregate amount of > > current switched by your IC, (2) the rise time of that current, and > > (3) the number and quality of the power and ground connections > > provided in the IC package. Most relevant to this discussion is the > > total amount of current--more capacitive loading enlarges that > > current, increasing the amplitude of SSO noise. >=20 > Why does more capacitive loading make SSO worse? >=20 > The previous discussion showed that you can compute the output resistance > of > the driver from the short circuit current. That doesn't depend upon the > capacitive loading. >=20 > I think that capacitive loading will make the duration of the output > current > pulse longer. It will slow down the rise time of the signal, but that's > the > voltage rise time. The current rise time is what causes ground bounce and > that won't change if you add more load capacitance. >=20 > What am I missing? >=20 > Is the turn-on time for a driver slow rather than instantaneous? "Slow" > meaning roughly the same as the (normal) rise time so the normal > capacitance > gets charged while the driver is turning on and the driver never delivers > the > full short circuit current? >=20 >=20 >=20 > -- > The suespammers.org mail server is located in California. So are all my > other mailboxes. Please do not send unsolicited bulk e-mail or > unsolicited > commercial e-mail to my suespammers.org address or any of my other > addresses. > These are my opinions, not necessarily my employer's. I hate spam. >=20 >=20 >=20 > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >=20 > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list >=20 > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >=20 > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ >=20 > List technical documents are available at: > http://www.si-list.org >=20 > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu >=20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu