74LS90 power-on auto reset - Page 2 - Electronic Circuits Projects Diagrams Free

ljcox · 20th December 2006, 04:02 AM

Quote:

Originally Posted by Torben

I've found the Schmitt trigger solution many times as it's obviously the preferred solution--and while I earlier stated that I didn't want to go that route for various reasons

Sorry, I did not notice your earlier comment.

Quote:

Originally Posted by Torben

(I think of the board with the counters and input debouncer/timers as ....

You may be able to use one of the input debouncers or timers for the power on reset (if there is a spare section in an IC, eg. one Schmitt spare in a Hex Schmitt or if you are using a 555, use a 556 and use the spare section for the POR.

Quote:

Originally Posted by Torben

I'm not sure if you're saying to connect the Schmitt trigger and then use the RC net you describe, or to just use the net right on the 74LS90 reset pins.

You could connect it directly to the 74LS90 reset pins if you wish, I prefer the Schmitt solution as it gives a "clean" pulse to the 74LS90 reset.

ljcox · 20th December 2006, 04:08 AM

Quote:

Originally Posted by audioguru

TTL eats power. Even LS TTL.

Yes, I gave TTL and LS away as a bad joke years ago. I prefer the 4000 series CMOS and the 74HC series.

audioguru · 20th December 2006, 04:18 AM

In the '70s I used TTL LS logic ICs. Then I tried Cmos and never used another power hungry TTL again.

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20th December 2006, 04:18 AM	(permalink)
audioguru	In the '70s I used TTL LS logic ICs. Then I tried Cmos and never used another power hungry TTL again. __________________ Uncle $crooge