Hi john: I haven't seen you for a long time! How are you reently! Let me try to answer your question. about power integrity on the board, the low frequency range is covered by VRM design (depend on Rout,Lout,Rflat,Lslew) and the high frequency range is covered by IC's(like as CPU) package. We can do nothing above 50 MHz from PCB level.the package and chip level should handle that power noise. All we have to do is to choose how many bulk caps ,ceremic caps and what value. of course,good power/GND pair design(physical shape) is helpful to lower power noise at very high frequency range. Because you can condider the PWR/GND pair as a big capacitor. The bulk cap is useful to lower dynamic impedance at 1K~1M range.the ceremic is applied to 1M~50M. But ,as you know,the lower cap's value ,the higher ESR value,so decap is more and more no effective on power integrity. As for the guideline to power noise you mentioned,it depends on how much IC can stand.For CPU's example usually,you can check CPU's datasheet(the relative EMTS of intel),the DC characteristic point out the tolerance. or find out that from the relative VRM design request of intel published. My remebrance is 5%. if i have some mistake,feel free to let me know.thank you! KEVIN hou assistant manager High Speed Signal Design Division RD7 , PSBU MiTAC Computer Inc. * 886-3-396-2888 Ext. 3231 * 886-3-327-7262 * houkevin@xxxxxxxxxx <mailto:houkevin@xxxxxxxxxx> -----Original Message----- From: John Lin (ªL´Â·×) [mailto:John@xxxxxxxxxxxx] Sent: Wednesday, October 22, 2003 5:52 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Power plane frequency range and noise level Dear all SI gurus, Could some one comment on what range of frequency we need to care for a power plane simulation? For example, for a power plane to support a chip with 800Mhz bus transition. What is the frequency range I need to set for simulation? And if the bus is 1.5voltage type, is ther any guideline to say the amount noise allowed on the power plane? Thank you for helps in advance. Best Regards John. ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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