Does an oscillator module need bypass caps?

[RogerRowland]

Maybe a stupid question but, I normally use just an external crystal (with load caps) when running my PICs at 20MHz, but now I've got hold of some oscillator modules - these ones http://www.ebay.co.uk/itm/20Mhz-Crystal-oscillator-TTL-HCMOS-8-pin-DIL-format-Qty-1-NEW-/111777853837? - because it saves me a desperately needed pin. All works well on breadboard, but I'm wondering if I need bypass/decoupling caps on the oscillator's power pins?

As you can see from the eBay listing, there's no datasheet in sight and Google hasn't helped.

I guess it wouldn't hurt, but is it normal to add bypass caps to these modules?

[Gyro]

Yes it does, treat it like a normal high speed logic chip. It might possibly have some limited internal supply decoupling but this will be severely restricted by package size so assume there isn't.

[RogerRowland]

Yes it does, treat it like a normal high speed logic chip. It might possibly have some limited internal supply decoupling but this will be severely restricted by package size so assume there isn't.

Ok, thanks for the quick answer - I'll make sure I add this to the schematic before I get PCBs made. 

[Gyro]

 

[bktemp]

All DIP8/DIP14 sized crystal oscillator modules I have opened had a decoupling cap inside, but you can't be sure unless you open each module, so add an external one.

[Ian.M]

Datasheet: http://www.quartz1.com/price/PIC/405N3134800.pdf

The test jig circuit has a bypass cap, so you should use one.  Also pin 1 is output enable and should be tied high.

[RogerRowland]

Datasheet: http://www.quartz1.com/price/PIC/405N3134800.pdf

The test jig circuit has a bypass cap, so you should use one.  Also pin 1 is output enable and should be tied high.

Excellent find with the datasheet  That's really helpful, thanks. The eBay description didn't mention the enable pin, which I guess is either pulled up internally or I just got lucky, because it works floating. I'll make sure to tie it high now. Thanks again.

[jwm_]

Datasheet: http://www.quartz1.com/price/PIC/405N3134800.pdf

The test jig circuit has a bypass cap, so you should use one.  Also pin 1 is output enable and should be tied high.

Excellent find with the datasheet  That's really helpful, thanks. The eBay description didn't mention the enable pin, which I guess is either pulled up internally or I just got lucky, because it works floating. I'll make sure to tie it high now. Thanks again.

I aquired about 200 20mhz oscillators just like that as part of an ebay score somewhere, after using about 4, having fun dremeling open some others and watching what happens when i take a sharpie to the crystal to tune it, I have roughly 190 left. If someone wants a couple I'll send em for the price of postage from southern california.

For some reason, occasionally those oscillator modules come up in bulk for insanely cheap on ebay, usually loose with bent leads. maybe someone knocks over a bin at the factory and they sweep em up and put em online? I never had issues , appear within spec according to my standard so I don't think they are factory rejects. I always use them for self-made boards to just not worry about getting the capacitance/layout right for stable crystal starting up. that and i have a couple hundred to use up... When all you have is a bin of 20mhz oscillators, everything looks like something that should run at 20mhz...

[Cliff Matthews]

I aquired about 200 20mhz oscillators just like that as part of an ebay score somewhere, after using about 4, having fun dremeling open some others and watching what happens when i take a sharpie to the crystal to tune it, I have roughly 190 left. If someone wants a couple I'll send em for the price of postage from southern california...

PM'ed Thanks!
I promise I won't be cruel with a sharpie, but how much deviation were you able to get? Any photo's?

[retrolefty]

When all you have is a bin of 20mhz oscillators, everything looks like something that should run at 20mhz...

 Love it. 

 I once scored like 25 50MHz crystal clock modules, just because I could.

[Electro Fan]

When all you have is a bin of 20mhz oscillators, everything looks like something that should run at 20mhz...

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