PCB Design Tips

Community Projects
1

Hey all!

I’ve been working on a project lately and decided to have an actual PCB fabbed instead of just using protoboard. This is my first time designing a PCB and was wondering if someone with a little more experience would mind taking a look at my design and giving some feedback and pointing out any issues.

I’ve attached a screenshot below. Also, here’s a link to my Eagle board file: https://dl.dropboxusercontent.com/u/16610659/Clock.brd, since the forums don’t seem to permit .brd attachments.

Thanks!

ML

2

Look good enough except where are the de-coupling caps on each chip?

Check on some other designs, like SparkFun’s boards, for a reference.

3

Agreed. Decoupling caps are a must.

4

Thanks for the feedback! From what I’ve observed, you mainly just want a cap in proximity to every IC. So, if this is the case, would just one be sufficient for the DS1307 and DS32KHZ?

5

Not really. What you want is a de-coupling cap at every IC and as close as you get to the chips Vdd and Vss (power + and -) pins.

These caps are to supply current when a chip’s internal circuits switch.

You might also want to increase the width of all power and ground traces. This may not be needed but will not hurt have wider traces = lower impedance.

6

Do you really mean to not have your Battery - not connected to anything?

7

I belive you dont see the ground plane fill. See the dotted line all around the cirquit…

8

I guess its been a while since I opened Eagle, but wouldn’t the battery ground trace also have a mark on it? Otherwise makes sense :slight_smile:

9

Thanks again for the feedback guys! I’ve added a 0.1uF cap near the VCC of each IC and beefed the VCC trace to 24 mils (vs. 10 for the rest).

@Ron: Thanks for the tip. I’m using a ground plane, so I think I’m clear there.

I’ve added another screenshot taking everything here into account, just in case I screwed something up in the interim. Again, thanks for reviewing my design. :slight_smile:

10

Which layer is your ground plane on?

Is this a 2 layer or four layer board?

If two layer then you may have a problem with the ground plane. So, show us the ground connections.

11

If it is just a double-sided board, try to have as few traces on the side with the ground plane. You really don’t want to have ground current having to go the long way around a trace that is cutting the plane.

Traces should hit pads at right angles; acute connections can cause acid traps

/mike

12

It’s a two layer with ground planes on both layers, as with just about any PCB I’ve seen, SF included (issue?). I’ve included some ground vias, so nothing should really have to “go the long way”.

@Mike: I did go into things knowing acutes were bad (one of the few things I knew :)), looks like I missed a couple when making some changes; thanks for pointing those out.

I’ve attached images w/ the planes filled in.