Think of PPM as a tolerance on the frequency. The smaller the PPM number the more accurate and stable the crystal frequency will be. Mike Poorman EMC Technician Cascade Engineering Services, Inc., Email: v-mipoor@xxxxxxxxxxxxx This email message may contain confidential and proprietary information. Any unauthorized use is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of bala Sent: Wednesday, December 14, 2011 2:17 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] ppm(parts per million)-Crystal OSC Hi all, I have a little confusion on PPM vs frequency of Crystal Oscillators.How important is the term 'ppm' than frequency.Why all the datasheets have both units,ppm and Hz.Please clarify,Also how much important is the value of ppm on the Signal integrity side,if any.Thanks for your time. -- bala ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu