Category:PCB PCB Design Rules

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Initially PCBs were designed manually by creating a photomask on a clear mylar sheet, usually at two or four times the true size. Starting from the schematic diagram the component pin pads were laid out on the mylar and then traces were routed to connect the pads. If you have many questions of PCB Design, please come here!

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PCB design for high-speed TTL Reply 2016-09-16 16:16:50
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Lukas Krehel

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I am designing high-speed TTL-based processor. I will be using fast AC, ACT and LVC series, so switching frequencies will be in 100Mhz range with 1-3ns fronts. I plan to use double-sided PCB, Bottom side will be VCC, top side will be GND with high-speed traces on it. Here are the questions: 1) What is optimal FR4 thickness for such high-speed schemes? 2) What is the optimal trace width for high-speed digital signals? 3) Do I need any termination for 5-10cm traces with 1-3ns fronts?
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Statement: This post is only the personal view of the author and does not represent the opinions of ALLPCB.com.

Kermit

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What is your highest clock frequency for your PCB?

Sezgin KIR

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The following is my answers for your questions: 1.Doesn't matter. You just need a different trace width depending on which you choose. 2. What is the optimal trace width for high-speed digital signals? There isn't one. You can choose a width to have a given impedance. 3. Do I need any termination for 5-10cm traces with 1-3ns fronts? At 1 ns and 10 cm, yes. At the weavelength is 30 cm, 20 cm at electrical speeds. 10 cm is almost half that, well above the guidelines.

Ivan Dario

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For your question about thickness,the optimal thickness would be less than 0.010" between your signal layers and your power/gnd planes. But since you have a 2 layer PCB there is no point in worrying about PCB thickness. The thickness will be whatever is required to give the board the mechanical strength required to hold all of your parts, about 0.0625".
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