Debouncing....at About 1Mhz

[Ken S. Tucker]

Hear ya, that's a good point. If going low is noisy it
will re-trigger the OR /RC combo, and send a fast
glitch through the Output.
Off hand I'd put a brief RC filter on the output to
change the glitch to a small bump.

Schematic, please.

I posted a schematic already, but it would appear
there is more interest in other ways, so I was
going to drop out of the thread and just lurk to see
where it heads to.

JF

Regards
Ken

 

[John Larkin]

This has got to be a classic signal clean up problem....

I need a circuit that triggers on edge A, then ignores about 0.1uS of
jitter then triggers on edge B and then ignores a following 0.1uS of
jitter.

+-+ +-+ +----------------+ +-+ +-+
In | | | | | | | | | |
A | | | | B | | | |
-------+ +-+ +-+ +-+ +-+ +-----------

|<0.1uS>| |<0.1uS >|
|< 0.5uS >|


Out +------------------------+
| |
A' B'
-------+ +-------------


Edge A to A' is ~ less than 10nS
Edge B to B' is ~ less than 10nS

All values are approximates.
"In" and "Out" are repeating waveforms.

I think I can do it with:

1 flip flop
1 >0.1us delay circuit
Sprinkled with gates..

Or maybe I need 2 flip flops..one for edge A and one for edge B..

I'm not even sure yet which type of FF to get.

If anybody has done this problem before and doesn't mind sharing..let
me know a topology...

In the meantime, I'll be doodling until I get a solution...


D from BC

Here's a single-prop-delay version, which could be done in about 3 ns
with one of the tiny-logic parts.

http://s2.supload.com/free/Schmitt.JPG/view/


I probably wouldn't do this in production, because the switch
thresholds of cmos schmitts aren't very tightly defined. My other
circuit is more predictable.

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John

 

[JosephKK]

John Larkin [email protected] posted to
sci.electronics.design:

OK, but a 9602 is 40 ns prop delay all by itself.

I think the entire thing can be done with a single schmitt trigger
gate, one prop delay.

John

You are welcome to any thoughts you want. Please remember that
the "input" is coming from a reasonably fast comparator as it is.

 

[JosephKK]

John Larkin [email protected] posted to
sci.electronics.design:

On Thu, 08 Nov 2007 09:43:07 -0700, Jim Thompson

On Thu, 08 Nov 2007 08:34:18 -0800, John Larkin
[snip]

I think the entire thing can be done with a single schmitt
trigger gate, one prop delay.

John

Show us.

...Jim Thompson


Oh come on, somebody give it a try first.

John

Stop being coy, John. Just show me, and I'll simulate it.

...Jim Thompson


It's too simple to bother simulating.

John

OK. So show me already.

...Jim Thompson

You want me to show all my cards, without a little raising and
passing and bluffing first? That's no fun.

Really, it's pretty obvious. Once you consider reducing the prop
delay to 1, it just pops out.

John

I think i see where you went, that is kind of slick. Has to be a non
inverting ST.

 

[JosephKK]

Fred Bloggs [email protected] posted to sci.electronics.design:

Is that 9602 the old Fairchild TTL one-shot? LOL, you must be old
...real old.

I think they made the original, i used some knock off a mere 20 years
ago. It did the job and was cheap. If i was trying to make a real
design today i would be looking for an AHCT equivalent.

 

[JosephKK]

John Larkin [email protected] posted to
sci.electronics.design:

Yup. After they both fire, roughly 40 ns after, the fun begins.

Another hairball, but at least it's a bit simpler. Still too slow,
even when it doesn't screw up.

John

Maybe, maybe not. Have you carefully analyzed all the propagation
delays? What happens with a fast AHCT equivalent (is the '221 close
enough?)?

 

[JosephKK]

John Larkin [email protected] posted to
sci.electronics.design:

Here's a single-prop-delay version, which could be done in about 3
ns with one of the tiny-logic parts.

http://s2.supload.com/free/Schmitt.JPG/view/


I probably wouldn't do this in production, because the switch
thresholds of cmos schmitts aren't very tightly defined. My other
circuit is more predictable.

There is likely a variant that uses slow negative feedback that
would be demonstrably reliable but preserves the 1-gate delay.
Haven't worked that one out, but it feels like there's something
there.

John

Would not work in this case. As previously stated signal is from a
comparator.

 

[John Larkin]

John Larkin [email protected] posted to
sci.electronics.design:


Would not work in this case. As previously stated signal is from a
comparator.

What difference would that make? The input is a logic level, and its
time behavior has been defined.

Yes, there is a simple fix that allows reliable operation with
real-world cmos schmitts. It's sort of obvious.

John

 

[Spehro Pefhany]

On Thu, 08 Nov 2007 07:14:28 -0800, John Larkin

On Thu, 08 Nov 2007 06:23:07 GMT, JosephKK

[snip]

Personally i would use a 9602 and a 7400 connected as a gated rs
flip-flop. R of 5K and c of 10 pf or so.

Schematic?

John

I finally managed to post one.
Decided on 20 pF instead.


OK, but a 9602 is 40 ns prop delay all by itself.

I think the entire thing can be done with a single schmitt trigger
gate, one prop delay.

John

Show us.

...Jim Thompson

Oh come on, somebody give it a try first.

John

Stop being coy, John. Just show me, and I'll simulate it.

...Jim Thompson

http://www.generiques-tv.com/covers/c5e3990a51ee2be86cd181a04b9d0336.jpg


Best regards,
Spehro Pefhany

 

[D from BC]

Here's a single-prop-delay version, which could be done in about 3 ns
with one of the tiny-logic parts.

http://s2.supload.com/free/Schmitt.JPG/view/


I probably wouldn't do this in production, because the switch
thresholds of cmos schmitts aren't very tightly defined. My other
circuit is more predictable.

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John

Neato..a differentiator warping the signal into the hysteretic
levels...
Nope...I didn't guess that one.


One wild idea I had was to try and use a 4.5nS LT latching comparator
in some fashion.. But nahhh..
(No I'm not affiliated with LT in anyway..)


D from BC

 

[Fred Bloggs]

It has the compensating virtues of being fast, being hazard free,
being simple, and doing exactly what was requested.

I'll give you simple, but the other descriptors are in your dreams. I
will not get into the details of the inferiority of your 'design' other
than to say even a chimp would know that mixing RC's into a first
occurrence event detector makes no sense.

Measuring the ugliness of your designs is like evaluating 0/0. You
belong to the Ladies Auxiliary of S.E.D. Hey, bring us another tray of
those little triangular roast beef sandwiches with the crusts cut
off... you do those so well.

Just more of your delusional fantasies...must be the Lipitor has
corrected your testosterone deficiency, how does it feel to be able to
grow a mustache for the first time in your life...

 

[Jim Thompson]

On Thu, 08 Nov 2007 13:37:30 -0800, John Larkin
[snip]

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John

Neato..a differentiator warping the signal into the hysteretic
levels...
Nope...I didn't guess that one.

[snip]

Neato! A non-repeatable "solution" ;-)

...Jim Thompson

 

[John Larkin]

I'll give you simple, but the other descriptors are in your dreams. I
will not get into the details of the inferiority of your 'design' other
than to say even a chimp would know that mixing RC's into a first
occurrence event detector makes no sense.

Clearly it needs some delay. Maybe I should have used Jim's magical
"Delay" black box.

I don't suppose you noticed that the RC drives the D pin of the flop.
Hell, you obviously don't understand the circuit at all.

So design and post something and quit whining.

Just more of your delusional fantasies...must be the Lipitor has
corrected your testosterone deficiency, how does it feel to be able to
grow a mustache for the first time in your life...

I've had one since I was 19. I was doing presentations to aerospace
companies, like Lockheed and Boeing, and I just looked too young. The
moustache helped a little. We got the contracts, so I suppose it did.

John

 

[John Larkin]

On Thu, 08 Nov 2007 13:37:30 -0800, John Larkin
[snip]

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John

Neato..a differentiator warping the signal into the hysteretic
levels...
Nope...I didn't guess that one.

[snip]

Neato! A non-repeatable "solution" ;-)

...Jim Thompson

Hey, Jim is actually Fred in disguise!

John

 

[Jim Thompson]

On Thu, 08 Nov 2007 13:37:30 -0800, John Larkin
[snip]

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John


Neato..a differentiator warping the signal into the hysteretic
levels...
Nope...I didn't guess that one.

[snip]

Neato! A non-repeatable "solution" ;-)

...Jim Thompson

Hey, Jim is actually Fred in disguise!

John

Waveforms that only droop the part of the waveform you WANT to droop
(trying to make your case) don't quite do that in the real world.

...Jim Thompson

 

[John Larkin]

On Thu, 08 Nov 2007 21:37:56 -0800, D from BC

On Thu, 08 Nov 2007 13:37:30 -0800, John Larkin

[snip]

There is likely a variant that uses slow negative feedback that would
be demonstrably reliable but preserves the 1-gate delay. Haven't
worked that one out, but it feels like there's something there.

John


Neato..a differentiator warping the signal into the hysteretic
levels...
Nope...I didn't guess that one.

[snip]

Neato! A non-repeatable "solution" ;-)

...Jim Thompson

Hey, Jim is actually Fred in disguise!

John

Waveforms that only droop the part of the waveform you WANT to droop
(trying to make your case) don't quite do that in the real world.

...Jim Thompson

Circuits process waveforms the way I want them to, because I design
them that way.

Are you suggesting that I don't understand how RC circuits respond to
waveforms? The only alternative seems to be that you don't. So you
must be Fred, qed.

John

 

[Jim Thompson]

On Fri, 09 Nov 2007 08:17:06 -0700, Jim Thompson
[snip]

Waveforms that only droop the part of the waveform you WANT to droop
(trying to make your case) don't quite do that in the real world.

...Jim Thompson

Circuits process waveforms the way I want them to, because I design
them that way.

Are you suggesting that I don't understand how RC circuits respond to
waveforms? The only alternative seems to be that you don't. So you
must be Fred, qed.

John

Funny, your circuit doesn't produce waveforms exactly as you sketched
them.

Put some numbers on a real circuit, post it, and then let the mob
evaluate its efficacy.

Or are you chicken ?

...Jim Thompson

 

[John Larkin]

On Fri, 09 Nov 2007 08:17:06 -0700, Jim Thompson
[snip]

Waveforms that only droop the part of the waveform you WANT to droop
(trying to make your case) don't quite do that in the real world.

...Jim Thompson

Circuits process waveforms the way I want them to, because I design
them that way.

Are you suggesting that I don't understand how RC circuits respond to
waveforms? The only alternative seems to be that you don't. So you
must be Fred, qed.

John

Funny, your circuit doesn't produce waveforms exactly as you sketched
them.

Of course not. That's why they call it a "sketch." And since the
component values aren't specified, it couldn't do anything "exactly."

Put some numbers on a real circuit, post it, and then let the mob
evaluate its efficacy.

Or are you chicken ?

So you *don't* understand it! That's interesting.

John

 

[Jim Thompson]

On Fri, 09 Nov 2007 09:27:11 -0700, Jim Thompson
[snip]

Funny, your circuit doesn't produce waveforms exactly as you sketched
them.

Of course not. That's why they call it a "sketch." And since the
component values aren't specified, it couldn't do anything "exactly."

Put some numbers on a real circuit, post it, and then let the mob
evaluate its efficacy.

Or are you chicken ?

So you *don't* understand it! That's interesting.

John

Your recent responses have become of such a subterfuge level I have to
conclude you're a leftist weenie. Bye!

...Jim Thompson

 

[John Larkin]

On Fri, 09 Nov 2007 09:27:11 -0700, Jim Thompson
[snip]

Funny, your circuit doesn't produce waveforms exactly as you sketched
them.

Of course not. That's why they call it a "sketch." And since the
component values aren't specified, it couldn't do anything "exactly."

Put some numbers on a real circuit, post it, and then let the mob
evaluate its efficacy.

Or are you chicken ?

So you *don't* understand it! That's interesting.

John

Your recent responses have become of such a subterfuge level I have to
conclude you're a leftist weenie. Bye!

...Jim Thompson

Well, either you see it, or you don't. I guess you don't.

John