EMI, Cross Talk, Ground Bounce

[samiam]

I am sure you all know the myriad of problems that can plague a digital
circuit on a PCB, most through the fault of that phenomenon called
INDUCTANCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I am trying to change the way I lay out circuits on double sided PCB's
that I build at home.

I have reading up on signal integrity issues and learning that perhaps
the way I have been doing things are flawed - ok TERRIBLY flawed.

The question I have for the gurus on here is this?:
assuming a situation where I dont go with the ideal layout method of
seperate ground and power planes (a 3 - 4 layer board minimum) is there
a way to get some of those sort of benefits on a two layer design?

I can only build double sided boards at home, so any suggestions on
optimal ways/methods of laying out signal/power/gnd tracks and vias to
best defeat the voltage drops between traces and the noise and cross
talk effects would be SINCERELY appreciated

 

[Hal Murray]

The question I have for the gurus on here is this?:
assuming a situation where I dont go with the ideal layout method of
seperate ground and power planes (a 3 - 4 layer board minimum) is there
a way to get some of those sort of benefits on a two layer design?

I'd start by making the bottom layer a ground plane.

That probably works OK for simple board. You have to find
some way to get decent power distribution.

You can get more "layers" by using wires, including helpers
for the power.

 

[Fred Bartoli]

samiam a écrit :

I am sure you all know the myriad of problems that can plague a digital
circuit on a PCB, most through the fault of that phenomenon called
INDUCTANCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I am trying to change the way I lay out circuits on double sided PCB's
that I build at home.

I have reading up on signal integrity issues and learning that perhaps
the way I have been doing things are flawed - ok TERRIBLY flawed.

The question I have for the gurus on here is this?:
assuming a situation where I dont go with the ideal layout method of
seperate ground and power planes (a 3 - 4 layer board minimum) is there
a way to get some of those sort of benefits on a two layer design?

I can only build double sided boards at home, so any suggestions on
optimal ways/methods of laying out signal/power/gnd tracks and vias to
best defeat the voltage drops between traces and the noise and cross
talk effects would be SINCERELY appreciated

Make your bottom layer a GND plane.
Use SMDs as much as possible, and work hard on placing the components.
Route the supplies with tracks and have a good bypass policy. If you
have the possibility to place the bypass caps on bottom side (and for
hobbyist boards you can) then do it.
That should, for reasonable hobbyists project, leave few tracks to run
on the bottom side and when you have to, do this on the shortest
possible distance. If you have some difficult case, still for hobbyist
use, you can easily live with a few additionnal jumpers, wires,...

I've made some moderately complex (~400 SMDs) high volume boards that
way and they were plain success.

 

[Joerg]

samiam a écrit :



Make your bottom layer a GND plane.
Use SMDs as much as possible, and work hard on placing the components.
Route the supplies with tracks and have a good bypass policy. If you
have the possibility to place the bypass caps on bottom side (and for
hobbyist boards you can) then do it.
That should, for reasonable hobbyists project, leave few tracks to run
on the bottom side and when you have to, do this on the shortest
possible distance. If you have some difficult case, still for hobbyist
use, you can easily live with a few additionnal jumpers, wires,...

I've made some moderately complex (~400 SMDs) high volume boards that
way and they were plain success.

In a pinch you can also buy jumpers in SMT. Often they are called "zero
ohms resistors". They come in the popular SMT resistors sizes and
probaby 1210 would be nice for hobby projects because that leaves a bit
more space to route underneath. My layouter would close his eyes and
tunnel a 0603 without breaking a sweat but don't do that for hobbyist
boards.

 

[Marra]

I would look for a decent PCB layout software that does autoplacing of
components for shortest nets

www.ckp-railways.talktalk.net/pcbcad21.htm

 

[JeffM]

Marra wrote WITHOUT CONTEXT[1]:

I would look for a decent PCB layout software
that does autoplacing of components for shortest nets

www.ckp-railways.talktalk.net/pcbcad21.htm

Full disclosure would be nice:
http://groups.google.com/groups/sea...9-orUyGBN00G0sVMjw&scoring=d&filter=0&num=100

....perhaps a proper sig:
http://www.google.com/search?q=two-hyphens-and-a-space+-stripped+-FWIW+-Suspensive
..
..
[1]
http://www.google.com/search?q=cach...up+before.the.original.*.*+*-for-your-readers

 

[Fred Bartoli]

Marra a écrit :

I would look for a decent PCB layout software that does autoplacing of
components for shortest nets

www.ckp-railways.talktalk.net/pcbcad21.htm

Almost always a sure receipt for disaster.

 

[Marra]

Marra a écrit :



Almost always a sure receipt for disaster.

Well it works for me !!!!

 

[Marra]

Marra wrote WITHOUT CONTEXT[1]:

I would look for a decent PCB layout software
that does autoplacing of components for shortest nets

www.ckp-railways.talktalk.net/pcbcad21.htm

Full disclosure would be nice:http://groups.google.com/groups/search?q=pcbcad21&enc_author=_U-3sxwA...

...perhaps a proper sig:http://www.google.com/search?q=two-hyphens-and-a-space+-stripped+-FWI...
.
.
[1]http://www.google.com/search?q=cache:ohQq8nqqThwJ:groups-beta.google....

You can use the power of the computer to move components around until
the optimum layout is achieved.
I leave mine on overnight processing.