Where to buy fast ceramic resonators

[Darrel Taylor]

You aren't planning to use them on a PIC are you?

25mhz is the highest you can go for a PIC oscillator.

[rmteo]

Actually it is 20MHz maximum for PIC16's and 40MHz for PIC18's using an oscillator in EC mode.

For crystals/resonators the maximum is 20MHz for PIC16's and 25MHz (10MHz if PLL is enabled) for PIC18's in HS mode.

[The Master]

Yes i was planning to use them with PICs. Im using 24MHz at the moment with PIC18Fs (i know 16Fs can only do 20). Im pretty sure 18Fs can handle upto 60MHz or atleast the ones im using can (according to the datasheet). Even 40MHz would be a help tho. Im struggling at the moment cramming all my PWM code and extras into the 6M instructions you can get with a 24MHz resonator. I will also be looking at writing the code in slightly different ways but a better resonator would help a lot.

Ill have a look at digikey. Ive already tried my local places but it seems that nobody really uses over 16MHz. Thanks for your help

[rmteo]

...Ill have a look at digikey. Ive already tried my local places but it seems that nobody really uses over 16MHz. Thanks for your help

That's because that is the highest that is useable with any PIC18 to get the fastest clock possible - 64MHz with the newer 3.3V parts.

[The Master]

Hmm, i think you might have to explain that one too me. Also, how come my 24MHz resonators work fine with a 18F?

I thought PICs ran instructions at a quarter of the speed of the resonator

[The Master]

The resonators i use dont need external capacitors (they are the 3 pin ones). Do i need to use a 2 pin one with caps?

Edit: My circuits are already working. I just want to speed them up a bit

[Darrel Taylor]

Hmm, i think you might have to explain that one too me.

Which part?

Also, how come my 24MHz resonators work fine with a 18F?

Because 18F's oscillate just fine up to 25mhz.

I thought PICs ran instructions at a quarter of the speed of the resonator

They Do.
But you seem to be missing the 4xPLL part.
Are you familiar with the 4xPLL?

The resonators i use dont need external capacitors (they are the 3 pin ones). Do i need to use a 2 pin one with caps?

That is simply my suggestion.
Do your development with a crystal.
When it's all working perfectly with the crystal, test it with a resonator while varying the ambient temperature to the furthest extremes you can or really need.

If everything still works, you should be OK to uses resonators for a production run.
add: If not, you can make allowances for the deviations from "nominal".

But having timing related problems that you can't find in the program, while you're trying to program it, really sucks.

Use a crystal.

[Darrel Taylor]

Buy a 10mhz crystal with 2-22pF capacitors.
Use the 4xPLL to get 40mhz.

You can not run a 40mhz crystal or resonator from a PIC's oscillator.

P.S.
Use a crystal. Resonators have their uses, and you can figure out if it'll work in your application, after you have your application working.