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
- posted
15 years ago
What's the difference between 4 pin and 2 pin clock crystals?
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- Vote on answer
- posted
15 years ago
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
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2 pin crystal
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-- Rich Webb Norfolk, VA
- Vote on answer
- posted
15 years ago
OK,
Here's the spec of what I'm looking at:
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So are the two series caps performing the function you mentioned?
- Vote on answer
- posted
15 years ago
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
- Vote on answer
- posted
15 years ago
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.
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