Author Topic: PIC24 capacitor value for crystal  (Read 3487 times)

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exapod

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PIC24 capacitor value for crystal
« on: May 16, 2014, 02:54:30 pm »
I want to use this crystal : http://it.mouser.com/Search/ProductDetail.aspx?R=TSX-3225_16.0000MF10U-B0virtualkey64320000virtualkey732-322516MF10U-B0 for a pic24 but i have a doubt on the capacitor value.
The datasheet says " Load capacitance : 7pF to Infinity " . What value should i use? I have some 12.5 pF, are they ok?
Thanks for the help.
« Last Edit: May 16, 2014, 02:57:26 pm by exapod »
 

Offline 22swg

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Re: PIC24 capacitor value for crystal
« Reply #1 on: May 16, 2014, 08:00:31 pm »
Its quite likely your 12pf  will only be around 10pF anyway will be fine, I am curious as to why you need external osc /  xtal  with PIC24 ?
Check your tongue, your belly and your lust. Better to enjoy someone else’s madness.
 

Online mariush

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Re: PIC24 capacitor value for crystal
« Reply #2 on: May 16, 2014, 08:24:47 pm »
Most need 12-18pF so what you have now should be good.
 

Offline 8086

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Re: PIC24 capacitor value for crystal
« Reply #3 on: May 16, 2014, 08:31:38 pm »
Always err on the side of caution, better go with infinity.
 

exapod

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Re: PIC24 capacitor value for crystal
« Reply #4 on: May 16, 2014, 09:45:34 pm »
Its quite likely your 12pf  will only be around 10pF anyway will be fine, I am curious as to why you need external osc /  xtal  with PIC24 ?

I need an external osc because i'm using the usb module.
 

Offline pipe

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Re: PIC24 capacitor value for crystal
« Reply #5 on: May 17, 2014, 08:48:39 am »
I need an external osc because i'm using the usb module.

Are you sure it works with a 16 MHz crystal for that? I've no experience with that PIC model but considering USB is 48 MHz, I would have expected that you would want a 6/12/24 MHz crystal, just to make the PLL a little easier. Maybe it doesn't matter.
 

Offline Psi

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Re: PIC24 capacitor value for crystal
« Reply #6 on: May 17, 2014, 09:07:36 am »
The crystal lists 16pf on the mouser page you posted
Greek letter 'Psi' (not Pounds per Square Inch)
 

exapod

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Re: PIC24 capacitor value for crystal
« Reply #7 on: May 17, 2014, 01:04:24 pm »
I need an external osc because i'm using the usb module.

Are you sure it works with a 16 MHz crystal for that? I've no experience with that PIC model but considering USB is 48 MHz, I would have expected that you would want a 6/12/24 MHz crystal, just to make the PLL a little easier. Maybe it doesn't matter.

Yes, the pic has a prescaler before the pll that generate the usb clock.
 


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