Rising and Falling Edge triggered one-shot

tedj121 · 2018-01-11T18:23:09+00:00

Hi, I'd like to take a long input pulse and trigger a much shorter one-shot pul se at its rising and falling edges. Ideally, only a single input should be required (i.e. the one long pulse) for minimal part count. I've looked ov er several timer ics and none seem to fit the bill or are too pricey like t he 6993s. Can anyone suggest an appropriate ic? I would think it a common enough function to warrant a dedicated chip. Thanks, Ted

Jan 11, 2018 42 Replies

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Martin Brown 8 years ago

I had a quick look at the ATM168 datasheet and not only does it support several decent power saving modes it also supports interrupt on any transition for certain pins whilst in a low power state.

You will have to write an interrupt handler but that need not be a very complex one just something that does whatever you want to do and returns to sleep mode again. You might need to deal with the situation where the down transition occurs whilst you are processing the up transition or vice-versa (but that would be a problem for a hardware one shot too).

So long as you keep the overall power consumption under 5uA you will find that in service battery life pretty much depends on ambient temperature and how badly stored the battery was before you bought it.

Regards, Martin Brown

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Joerg 8 years ago

That's what depletion mode FETs and charge pumps are for :-)

Regards, Joerg http://www.analogconsultants.com/

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Joerg 8 years ago

I'd say nearly all of us.

Absolutamente. Ted would be missing out on most of the good stuff these days. I adopted SMT in 1986 and never looked back. It's actually easier to hand-solder than through-hole, no constant turning around of the board, nothing falls back out because the wires weren't bent sideways enough. Another nice thing is that resistors and capacitors can be stacked for trimming experiments or when the correct value is not at hand.

Ted: You can get what is often called "surfboards" that adapt SMT to through-hole. You could also just use those "copper-striped" boards and cut or score out a center line in each strip which would give you the

0.05" spaing of SO packages. It's easy once you get the hang of it. For soldering fine stuff the ETS tip for Weller irons works great.

Horror story that really happened: A friend was soldering a digital through-hole board, didn't immediately notice that one IC had slipped out when turning the board, the phone rang, he got up, pushing himself off the table with one hand .... YOOOUUUWWEEE ... all IC pins were solidly embedded in his palm. He had sort of a DIP-16 tattoo for a long time.

Regards, Joerg http://www.analogconsultants.com/

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