??? 04/13/09 21:07 Read: times |
#164560 - When I am in a hurry ... Responding to: ???'s previous message |
Which is quite often ...
I solder a 1K-ohm resistor between pins 13 and 12 and another between pins 10 and 11 of a 74HC04. Then, I solder a 150 pF cap between pins 12 and 11 of that same IC. Then I solder a wire between pins 10 and 9, and then, last but not least, I solder a crystal, and this has worked well for crystals ranging from 4 MHz to 15 MHz, though I admit it could be better if more carefully designed, between pins 13 and 10, and VOILA! I have a 14-pin oscillator with its buffered output at pin 9, where it would appear on a commercial oscillator can, with its complement at pin 10 and can, actually, use the remaining inverters in the package for something else, including another oscillator with its output on pin 6. When I do the latter, the interaction between the two is not easily observable, so I assume it's safe. I've been doing this since the '70's, though it's much easier with 0603 or 0805 components than with the old through-hole types we used in the '70's. I've found that this works with 74C04's (~CD4069), though it's somewhat frequency limited, 7404, 7414, 74LS04, 74LS14, 74ALS04, 74ALS14, 74HC04, 74HC14, 74HCT14, 74HCT04, 74AC04, 74ACT14, 74S04, 74S14, and 74F04. I haven't tried it with every conceivable hex-inverter in that pinout, but I suspect it would work just as well. I've used the same circuit in wire-wrap, and on PCB, and with SO components on PCB as well. I can't imagine why someone would want a 5- or 6- pin component, since that would probably mean large up-front NRE charges. RE |