4 Layer PCB Design 4

[lbb7]

I'm currently working on a 4 layer PCB design. I have to differnet voltages: 120Vac and 5Vdc. Since I'm pretty new to this I'm wondering what the best stack would be for power and ground. Should I keep the voltages completley seperate? Any suggestions or explanations would be much appreciated. Thanks!

 

[MacGyverS2000]

Absolutely separate! In fact, for isolation you need to keep a certain distance between the two. Don't know what you're doing, but usually a small portion of a PCB is designated for 120VAC power supply, the rest is covered with 5V POWER/GROUND planes.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[MikeHalloran]

Try restricting the AC to a small _area_ of the PCB, not a layer of its own, and keep everything else out of that area. That removes at least one layer from your PCB.

For incentive, remember that modern televisions are made on single sided boards. Do you _really_ need more than two layers?



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

Make sure you are not pushing the design rules on a AC portion, and make REALLY sure that no copper comes close to the edge of the board. I once saw a converter board ignite because the traces went to the edge of the board and arced and shorted to a ground plane.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[americancircuittech]

Since you choose a for 4 layer PCB for your current design, here's my suggestion for the layer stack up based on my experienced. Make sure that have separated the power plane from the ground plane.Usually, the third layer is designated to be the power plane and second layer for the ground plane. To avoid ignition according to one reply, follow the 20-H Rule by W. Michael King(

http://www.edaboard.com/thread3717.html).

While the first layer is for high speed clock traces and the fourth layer is for low speed signals. Use smallest distance between ground plane and power plane for lowest power impedance.This configuration enhances flux cancellation between the signal and the ground planes rather than the power planes.

There are some PCB related articles at

http://www.act-cw.com

under the articles section, and a lot of them are specifically about circuit designs.

Let me know if you have any more questions, or need more clarifications. Send me a message also if you need more elaboration.

 

[lbb7]

Hey, thanks for the suggestions and articles/websites. I really appreciate the help. I'm going to make sure that I really need a four layer board to complete my design. Thanks again everyone!