SMD Crystal or equivalent for MCU - Page 1
Forum section: electronics / beginners

author: FrankT
author_rank: Regular Contributor
timestamp: February 04, 2015, 07:44:44 am
content: I'm looking for a small SMD crystal, or equivalent, for my micro-controller circuit.I have always used through hole crystals, either the HC-49 package or cylinder type, but they always look monstrous compared to the rest of the circuit.This will be for an ATTINY45 with an 8MHz crystal. I need accurate timing and repeatability.Any recommendations for hand SMD solderable crystal packages? Or are resonator circuits an option (software guy here, I don't really know the differences)Thanks,Frank

author: Araho
author_rank: Regular Contributor
timestamp: February 04, 2015, 08:39:22 am
content: Have you tried looking through Digikey? They have an excellent system for finding parts like this, where you know both the name of the part and the value.Hereis a link to all SMD crystals with a frequency of 8MHz. You can further sort by size, load capacitance, stability and a whole host of other criteria.Standard SMD crystals with a formfactor like this can be hand-soldered easily.

author: FrankT
author_rank: Regular Contributor
timestamp: February 04, 2015, 08:46:39 am
content: Thanks for the reply.That's the type that I always seem to find. SMD, yes. But they are the same physical size as the through hole equivalent. Even the lower profile ones, are still 10x3mm, twice the size of the MCU.

author: sleemanj
author_rank: Super Contributor
timestamp: February 04, 2015, 08:56:43 am
content: How accurate do you need?http://jorisvr.nl/arduino_frequency.htmlCeramic resonators can come in very very tiny packages, at the expense of less accuracy and stability, 0.1% to like 0.5%.Difference is accuracy/stability, with resonators much better than the internal RC oscillator, and crystals much better than resonatorsI have a few of these3.2mm x 1.3mm ceramic resonatorson my desk at the moment waiting for me to use them, very very tiny.

author: FreddyVictor
author_rank: Regular Contributor
timestamp: February 04, 2015, 09:01:46 am
content: how aboutthese- size is 5mm x 3.2mmyou can make the land pads a little bigger if you don't have a re-flow station

author: FrankT
author_rank: Regular Contributor
timestamp: February 04, 2015, 10:59:43 am
content: Quote from: FreddyVictor on February 04, 2015, 09:01:46 amYes, that's what I'm looking for. I don't know why I couldn't find them. On the digikey website, I ended up with on 17 items, and they were the old clunk HC49 style case.I will also have a look the ceramic resonators. My project is to drive RC servos and control the position based on the current draw, so I don't think it needs to be accurate, just not drift over time.

author: sleemanj
author_rank: Super Contributor
timestamp: February 04, 2015, 11:14:49 am
content: Quote from: FrankT on February 04, 2015, 10:59:43 amIf a resonator works (and I'd think it probably would), then you get the advantage of not needing the two capacitors a crystal needs which can save quite a bit of space too.

author: Araho
author_rank: Regular Contributor
timestamp: February 06, 2015, 02:59:14 pm
content: Sorting by size on my previously linked list, after checking "In stock", I found this:http://www.digikey.no/product-detail/en/NX3225GD-8MHZ-STD-CRA-3/644-1178-1-ND/31255673.2mm by 2.5mm seems small enough, right?A little bit further down I also found the same as mentioned above by Freddy. It pays off to learn to use the parameterized search!