I have a couple TI SN74123 chips, but I'm having some trouble deciphering the datasheet to find out how to make a simple REPEATING pulse from this chip. In fact, I can't even get the thing to pulse once.

I would like to make a one-second pulse, then go low for 0.25 sec, then pulse for a second again, over and over until the end of time (I'm testing a relay). Does anyone, by chance, have a quick diagram that accomplishes this with the SN74123.

I've been trying to simulate it on Capture/Pspice A/D, but that program was written by infantile monkeys, and none of their SN74123 symbols has a pspice model associated with it.

Originally Posted by UberGeek

See the circuit titled "Low Power Pulse Generator" in this document:
http://focus.ti.com/lit/an/sdla006a/sdla006a.pdf

Your first stage will have a period of 1.25sec and becomes the trigger for the second, which will have a pulse width of 1sec.

UberGeek, you are the MAN! :wink: I don't know why I couldn't find that doc., but thank you very much!

B