Crystals

[YAN-1]

Hi. I was looking at the 16F87X data sheet because I want to know which crystal/resonator to buy for my PIC. However, I got mixed up. I remember that we used a ceramic resonator at the university labs that connected directly to the OSC1 and OSC2 pins without any resistors and capacitors; but the data sheet recommends 2 Cs and a resistor for proper operation. And how do I know what crystal frequency to get? If I am interesested in fast PIC operation, should I go to the 20 MHz limit? And as for the recommended capacitors in the data sheet, don't they have a voltage rating? (I thought I have to specify both capacitance and voltage rating to the seller when I go to buy one). Thanks.

 

[eblc1388]

(I thought I have to specify both capacitance and voltage rating to the seller when I go to buy one). Thanks.

I bet they don't teach things like capacitor voltage rating anymore these days in universities.

I think capacitor with 1000V rating would be sufficient and give good margin if the PIC is powered by +5V. :evil: :evil:

 

[YAN-1]

Yeah I was expecting such an answer! :lol:

 

[Jay.slovak]

Hi. I was looking at the 16F87X data sheet because I want to know which crystal/resonator to buy for my PIC. However, I got mixed up. I remember that we used a ceramic resonator at the university labs that connected directly to the OSC1 and OSC2 pins without any resistors and capacitors; but the data sheet recommends 2 Cs and a resistor for proper operation. And how do I know what crystal frequency to get? If I am interesested in fast PIC operation, should I go to the 20 MHz limit? And as for the recommended capacitors in the data sheet, don't they have a voltage rating? (I thought I have to specify both capacitance and voltage rating to the seller when I go to buy one). Thanks.

Some ceramic resonators have capacitors build inside. As for crystal frequency, anything from 4-20 Mhz will work fine, mostly PICs spend their time with doing nothing :lol: (eg. Delay loops), so speed is never issue (unless your project is really big and is using tons of Mathematical functions). Ceramic cappacitors are usually rated for 50V, si I think that 5V PIC won't burn it 8)