trying a smd version

Other Hardware 3rd Party Boards
1

I'd like to create a smd board of my project, using the surface mount ATMega328 - TQFP

I'm not sure what else I need with it. Looking at the eagle files for Sparkfun's pro mini, I see a crystal that has 3 pads.
It seems that normally you need a 16mhz crystal, and two 22pf caps, but the pro mini doesn't seem to have the caps. Can someone please tell me about this smd crystal?
Sparkfun does sell this one:

...but it isn't the same one as the pro mini uses, because it has 4 pads. But if it would work, that'd be fine. Do I need 22pf caps with it?
thanks.

2

(deleted)

3

ok, thanks.

4

t seems that normally you need a 16mhz crystal, and two 22pf caps, but the pro mini doesn't seem to have the caps. Can someone please tell me about this smd crystal?

They're using a resonator instead of a crystal...basically it has the caps built in. 2 pins go to the regular chip clock connections, the 3rd pin goes to ground. As spycatcher2k says, they're not as accurate as crystals.

...it has 4 pads....

If you look at the data sheet you'll see that 2 of the pads on SparkFun's SMD crystal are just for anchoring -- the crystal itself is on pins 1 & 3.

If you're interested in a SMD crystal, here's the one I've been using:

Good luck!

5

thanks. I'll go with that crystal you use.
I'm going to use the ATMega328 - TQFP
I'm finding there are dozens of the same part to choose from. If someone has a minute, could you verify that these will work:
22pf for the crystal: http://parts.digikey.com/1/parts/63505-cap-cer-22pf-50v-5-np0-0805-c0805c220j5gactu.html

5 volt regulator:

10uf filter for 5 volt side of voltage regulator

100uf filter for 12 volt (power in) side of voltage regulator

0.1uf cap to put next to ICs, like motor driver ic, etc

I think I got the right types of capacitors, but not sure...

I'm looking forward to trying surface mount project. Too bad there isn't a tiny surface LCD display, just big enough to display time.

6

The caps look OK to me. I haven't used any 0603 parts because of the size, but you're probably more dexterous than me so you may be OK.

I don't know that much about voltage regulators so I can't help you out with it, but I'm interested so please let me know how it goes.

7

If you want a slightly smaller footprint crystal I like this one a lot.

8

603's are just as much as a pita as 805's if you have properly spaced pads IMO

9

If you want a slightly smaller footprint crystal I like this one a lot.

That looks great, thanks. Do you happen to have an Eagle part for it?