SMPS PCB layout

[cm961]

Hey guys,

I've been putting together plans for my SMPS (based on Rod Elliots) and I'm wondering about PCB design. Everyone keeps saying use careful layout, but what does that mean? Put the caps near the chips, make everything compact, and use really large traces?

Pete

[jackinnj]

trace leads short and fat -- N-Channel can probably opine more knowledgeably -- but you are dealing with a square wave which wants to switch very quickly, and the loss across a trace is a function of the inductance -- Nat Semi has somePCB layouts on their website, so does ON-Semi. These will give you a good idea of where you are headed.

There are better chips these days than the SG3524 LM3524, LM3525 -- and don't be afraid of surface mount -- it can be done by hand!

[theChris]

also, i think grounding becomes an issue. basically look at everything that isn't perfect and see if it isn't what it is. example would be using a capacitor that has a large lead inductance, at some frequency the cap becomes an inductive load.

i'm not sure what frequencies and how demanding all this is though, at some level a ground plane would be nice, at others seperate ground paths, and for others, both (with capacitive coupling to the ground plan)