The higher the load capacitance of the crystal the more stable frequency it will have

[foxhenry]

hi guys, for crystal ic's the higher the load capacitance of the crystal itself will have a stable frequency or what? thanks..:?:

 

[Awarapunshee]

crystal load

As far as I remember, Load capacitance has the effect of increasing the frequency of a crystal.

 

[GSM Man]

crystal loading cap

Yeah, put a Big Cap on there and it will stop oscillating - that's pretty darn stable!

The capacitor value must be matched to the crystal and circuit. The crystal wil have a load capacitance spec that must be met for it to oscillate at the specified frequency.

What do you mean by stable? Frequency vs. Temperature?

 

[pauloynski]

crystal load vs frequency

The caps are the load to the crystal and may affect its frequency. This frequency change has a limit, otherwise it will not oscillate. Here is a good explanation **broken link removed**

 

[foxhenry]

load cap on crystal

Yeah, put a Big Cap on there and it will stop oscillating - that's pretty darn stable!

The capacitor value must be matched to the crystal and circuit. The crystal wil have a load capacitance spec that must be met for it to oscillate at the specified frequency.

What do you mean by stable? Frequency vs. Temperature?

hi gsm man, thanks for the reply..agree that it should be match to the crystal...just want to know because there are crystal from the market with the load cap of 16pF, 18pF, 20pF, 32pF.. so load cap with higher value is a good choice or the lesser load cap value?

and i got a circuit with 12mhz and crystal load capacitance itself is 20pF and i put a parallel cap on it with 18pF each... would it be okay?

thank you.

 

[M!k]

crystal load cap

and i got a circuit with 12mhz and crystal load capacitance itself is 20pF and i put a parallel cap on it with 18pF each... would it be okay?

Please read the application note mentioned above. There's a calculation on page 2, below figure 3.
Now if CL = 20pF, C1 = C2 = 18pF and Cs = a few pF, you'll see that it's not OK. C1 should be increased to e.g. 33pF.

Btw. most probably you won't recognize the frequency drift of a few ppm when using 18pF caps .....

 

[foxhenry]

18 pf load

thank you guys for all the replies

 

[darinyou]

load capacitance of crystal

hi all i have crystal ocilator with 74hc04 and hosonic 6.0000 b303 crystal i have proplem how i can get cl for this crystal to calculate c1 c2

regards