I'm a new hardware design engineer. I have a few questions about high speed pcb design.

1) when I search high speed pcb design, I saw pcb routing like snake. What is this ?

2) When I draw a high speed way (like can-bus line), I used differential pair. Can ı use with only differential pair at all high speed line ? Or Should I do different things ? Like lenght matching.

3) How many MHZ after a line being high speed line?

  • \$\begingroup\$ Your 1st question was previously asked here. \$\endgroup\$ – The Photon Jul 23 '19 at 20:00
  • \$\begingroup\$ Post a picture that shows your question 1 problem. \$\endgroup\$ – TimWescott Jul 23 '19 at 20:02
  • \$\begingroup\$ Your 3rd question was previously asked here. \$\endgroup\$ – The Photon Jul 23 '19 at 20:05

1) It's extra parasitic inductance built into a trace.

2) No, there are many way's to create a transmission line.

enter image description here
Source: http://www.gsm-modem.de/M2M/m2m-faq/transmission-line/

3) Roughly 50Mhz, after that transmission line effects start to take hold.

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1) to match lengths of wires in the differential pair, and in case of buses with multiple parallel differential pairs, to match the length of all pairs.

2) a little difficult to understand what you are asking. But if some interface is differential then use it. Match lengths but only up to what is necessary and practical - don't aim for 1mm length difference if 10mm is irrelevant.

3) that would depend on context. RS485 is differential but you can transmit at 1 bit/s rate or 10M bit/s rate. Coaxial SPDIF audio can be 12.288 Mbit/s or more but is not differential. Mostly the signal is defined by the slew rate of the edges.

4) most likely yes, but currently I can't suggest a source other than search engines and wikipedia about the subject to find books that match.

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