Re: Initializing a Flip-Flop on Power-up
- From: Jim Thompson <To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx>
- Date: Fri, 17 Feb 2006 17:51:28 -0700
On Sat, 18 Feb 2006 00:44:37 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
Hello Jim,
Douwe Egbert makes coffee too? I used to smoke their Cavendish until
the management decreed no smoking in the new house ;-)
Ah, a pipe smoker. Did that in my 20's for a couple years, on and off.
Usually Skandinavik Mixture or Irish tobaccoes. That, and a nice glass
of single malt.
I smoked primarily Dutch Cavendish from age 18 to age 54.
IIRC coffee is Douwe Egbert's mainstream product. But Frank would know
better, it's been two decades since I lived in the Netherlands. And I
always liked the other brand better, Kanis&Gunninck or something like that.
Personal opinion: Anyone who relies on an edge detector for POR is a
bit of a fool. In recent months it's been an almost weekly event to
patch some chip that won't POR properly.
Agree. It's pathetic what young engineers consider a POR these days.
It's actually sad that they have to make a distiction between POR and
BOR. Every reset should be good enough on brown-outs. What's really sad
is that even our (rather expensive) Motorola cordless phone appears to
perform dirty resets on occasion. Got enough honey-do projects so I am
not going to fix their design.
When VCC is low or the circuits are picky I use a BJT because it makes
for a better threshold. Or a TLV431 but that's expensive. If there is a
regulator I take it off before that and after, then issue the reset
before it is too close to dropout.
I prefer a level detect with hysteresis AND delay... easy to do if the
chip design includes my bandgap reference ;-)
Us circuit designers have to pay extra for that bandgap. But a
hysteresis is a good thing though I have to confess that I sometimes
forego it, but only if there is enough margin between threshold and the
circuit actually conking out. Plus enough decoupling capacitance to tide
it over the reaction time.
Regards, Joerg
http://www.analogconsultants.com
I live the fun life... if I need a bandgap I just roll one... designed
one last week that consumes only 5uA and comes fully alive at 1.5V
input. Includes a POR.
...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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