PCB layout with MAX6675

Community PCB Design
1

Hey there,

I’m confused about the correct layout for the thermocouple connections to a MAX6675 and was hoping someone could clarify for me.

The datasheet shows that you need to ground T- as close to the GND pin as possible. It also says to use a ground plane. However, should you keep the T- trace separate and just link it to GND close to the IC or can the T- pad just be connected directly to the ground plane?

I didn’t think about it initially and when I made the ground plane I got the following which just looks wrong.

http://www.flickr.com/photos/shareef_jalloq/4263396026

Thanks.

2

I’d keep the T- trace separate from the ground plane. It probably won’t make much difference, though.

Leon

3

Thanks Leon, done.

4

Is that a decoupling cap? You should put that above the chip, inline with the power, not after it like it’s doing now.

If not, then sorry, I’m real lazy today.

5

Yes it is a decoupling cap. I’m a bit of a noob at this but I thought that as long as it was close to the power pin then it was alright?

The PCB has been sent off now so I can’t change it but I’d appreciate being put straight on this issue so I can correct it next time.

Thanks.

6

You need to think in terms of current flow when connecting decoupling capacitors, otherwise they will be ineffective.

7

So this brings up a question that I probably should have asked a while back but…are there any good resources out there for PCB design? It’s a subject that I’ve always found harder than others to find detailed examples/information on the web.

Are there any good texts available or is it a better idea to just post PCB’s and ask for critique? I’m sure I’m loads more mistakes that would be easy to fix.

Thanks.