On Sun, 30 Sep 2007 10:15:33 -0400, "robb" wrote:


"John Larkin" wrote
in message ...
On Fri, 28 Sep 2007 16:28:23 -0400, "robb"
wrote:

Looking for constructive criticism on my plcc/dip adapter ?

Here's a similar thing. A 4M sram chip is soldered on top, and
it
plugs into an EPROM socket, so we can load and test code during
development. One extra pin picks up the uP /WRITE line, so we
can
write to the ram, and one other pin lets us pick up +5 or +3.3
for
power.

All that stuff about stress and angles and teardrops is pretty
silly,
at least if you do plated-through holes.


Thanks John,
for all the help and taking time to paste an example i really
appreciate the suggestions everyone has made.

Probaby no plated through holes this go around, though making a
copper electro-plating tank for through holes sounds like fun.

If you don't plate, put big pads on both sides, and solder on both
sides. That will help prevent ripping pads off.

The plating thing is very nasty. Just buy plated-thru boards from a
cheapie proto shop, APCircuits or such.


I have asked other this as well, how do i choose a capacitor
value for the bypass capacitors, and is there a best location to
place this.

0.1 uF ceramic usually works. Further discussion would start a
religious war. Ignore anything else that anyone says.

Place it close to the power pin(s) of the chip, and pour as much
ground as you can, which is what my board does.

I also noticed some resitors in your example ? what
purpose do they serve and would i want something similar ?

Those are zero-ohm jumper sites, so we can power the sram from +5 (the
regular pin) or from the 3.3 volt oddball pin. So far, we've just used
+5, but that may change some day.


thanks again for the helpful advice i hope to post a redo
shortly.

One thing i di not quite understand was the point about moving
vias out from under the chip ? seems like alot of unused space
and a great place to dump the vias if you want to keep the
overall package dimensions down ??

With plated holes, the vias are flat. If you use wire jumper vias, you
have to deal with the solder bumps on top, under the chip, which is
probably no big deal.

What sort of PLCC chips will you be using? What's the overall circuit
going to do?

John