Hi Scott,
First, I think we all need a bit more information for a specific response. Such as: - what is the clock frequency? - what is the clock rise time? - what is the clock signal amplitude? - overshoot or undershoot? - are these clock traces impedance controlled? - stripline or microstrip? And, you probably won't get a specific response anyway. That's what consultants are for. :-) But for rules of thumb with clock traces (and other high energy traces), it is important to keep layer changes to a minimum, if not zero, and keep them routed away from other susceptible traces to reduce crosstalk. In general, use a series termination located next to the output pin. Also, almost always avoid trace branches for clock traces. Its also important to keep everything well decoupled. IHTH. Best regards, Ron Pickard [email protected] owner-emc-pstc@majordo mo.ieee.org To: [email protected] cc: 10/24/02 10:20 AM Subject: High Speed Clock Routing Please respond to Scott.Mee All, I have a question regarding trace routing for high-speed clock signals. I have one driver, and two receivers. The distance between the driver and 1st receiver is roughly 2.5cm, the distance between 1st receiver and 2nd receiver is 3cm, and the distance between driver and 2nd receiver is 3.5cm. I actually have 2 questions: 1) What is a good rule of thumb for routing and termination of this high-speed clock trace? 2) Is daisy chain routing preferred (meaning driver to 1st receiver, then 2nd receiver), or should 2 traces of equal length be routed, 1 to each receiver (each of these two traces will have twice the impedance of the single trace emanating from the driver so that impedance matching will be maintained)? Any information, in general, or in specific on the subject is greatly appreciated. Thank you. Best Regards, Scott Mee Johnson Controls Inc. Automotive Systems Group EMC Product Compliance 616.394.2565 [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
