Re: Initializing a Flip-Flop on Power-up

On Fri, 17 Feb 2006 10:08:46 -0600, Dan Charette
<dan@xxxxxxxxxxxxxxxxxxxx> wrote:

Hi All!

I've got a small toggle circuit that I'm using to drive a shutdown
circuit on an audio power amplifier. The circuit is made from a
CD4093 Schmitt trigger NAND configured as a debouncer for my mute
switch input. The output of the 4093 is fed into a CD4013 fo provide
toggling cabability. I've got S and R tied directly to ground. But,
I'd like to explore the possiblity of providing a predictable power-up
scenario. Currently, the circuit upon power up will default to one
state or the other. What are some methods that you fellas have used
to achieve a known state consistantly with a flip-flop like this when
the power supply is from a single source. First gut instinct that I'm
thinking is to make some sorta RC timing circuit on the power supply
pin so that I can provide the set or reset pins with something known
before the power supply pin comes up. Any thoughts? Also, I don't
want to add too much additional circuitry... if I can solve this
purely with passive components or a few transistors, that'd be great.

Thanks!

You are on the right track. Surf on POR or "power on reset".

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

It's what you learn, after you know it all, that counts.
.

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