I have a circuit requiring a 25MHz clock signal, all the components I can find are 4 pin 25Mhz crystals - how do these differ from the 2 pin crystals in my spec?
Dave
What's the difference between 4 pin and 2 pin clock crystals?
May 15, 2008
4 Replies
Links to what you have found and what you're looking for would help.
*Probably* what you're calling "4 pin crystals" are canned oscillators. These take in Vcc and ground and then output a clock signal. Using one relieves you of the need to match the load capacitors to the "bare" (2 pin) crystal. They also typically have enough drive capacity for additional clocked logic, if needed, where many microcontroller crystal oscillators may not. 4 pin oscillator
formatting link
2 pin crystal
formatting link
Rich Webb Norfolk, VA
OK,
Here's the spec of what I'm looking at:
formatting link
So are the two series caps performing the function you mentioned?
Yes. The whole assembly of [74AC04 + 1 Mohm + crystal + caps] is conceptually what's packaged inside of a canned (4-pin) oscillator.
Rich Webb Norfolk, VA
If you go with the four pin part you can dump the 74ac04, the 1M resistor, the Xtal and the two 15pf caps.
Just add power and ground and send the output to pin7 of the ir drive.
-----------------
formatting link
- *Completion*Retention*Speed* Access your favorite newsgroups from home or on the road
-----------------
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required