d-flop one-shot

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

I get better hits using the term "monostable":

<https://www.n5dux.com/ham/files/pdf/Working%20With%20Monostable%20Multivibrators.pdf>

Fig 9 is about as simple as it gets. I don't understand why the extra
flop and the low pass and stuff after the button in the link you posted,
it's like they never heard of a passive differentiator before.

john larkin

2024-07-10 21:07:55 UTC

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/Working%20With%20Monostable%20Multivibrators.pdf>
Fig 9 is about as simple as it gets. I don't understand why the extra
flop and the low pass and stuff after the button in the link you posted,
it's like they never heard of a passive differentiator before.

Yikes, 36 years old. CD4000B logic.

I like d-flop one-shots because they are fast, truly edge-triggered,
and can be gated with the D input.

But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Cursitor Doom

2024-07-10 22:50:54 UTC

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Post by bitrex
Fig 9 is about as simple as it gets. I don't understand why the extra
flop and the low pass and stuff after the button in the link you posted,
it's like they never heard of a passive differentiator before.

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

john larkin

2024-07-11 00:16:56 UTC

On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.

I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.

I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.

Some people think one-shots are evil, but I like them.

Bill Sloman

2024-07-11 06:50:16 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.

Probably not. Signal routing is a problem that's hard to manage if you
don't have lot of control over where the signal goes, and can't add
shielding tracks alongside sensitive signal paths.

Post by john larkin
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.

I had one famous success when I was in the Netherlands, when I added an
ECL front end to a basically TTL delay generating device. Changing Vcc
levels shifted the output edge by an appreciable fraction of a
nanosecond in the original TTL-only system. Shifting the edge-generation
into ECL and taking the TTL output edge from an ECL-to-TTL converter
reduced the timing jitter to undetectable levels.

Post by john larkin
Some people think one-shots are evil, but I like them.

They certainly can be, but they can equally be very useful.

You'd be well advised to look carefully at the emitter coupled
monostable, and work out exactly what it does when it starts generating
it's output pulse.

This isn't trivial

https://ieeexplore.ieee.org/document/1643426

but it is worth doing.

If the two transistors in the simple emitter-coupled monostable are
BFR92A parts it can produce a one nsec wide output pulse. It can also
oscillate if you don't manage the base driving impedance carefully.

Faster parts could do better, but can be even harder to keep stable.

--
Bill Sloman, Sydney
--
This email has been checked for viruses by Norton antivirus software.
www.norton.com

bitrex

2024-07-11 16:01:02 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

Post by john larkin
If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.
Some people think one-shots are evil, but I like them.

The supply to delay variation in the Greenpak SPLD 16 bit counter
configured as a one-shot is around 10, in simulation anyway..

bitrex

2024-07-11 16:23:25 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.
Some people think one-shots are evil, but I like them.

The supply to delay variation in the Greenpak SPLD 16 bit counter
configured as a one-shot is around 10, in simulation anyway..

I'll try to measure it this weekend, I'm interested to see. What general
length of one-shot are we talking?

john larkin

2024-07-11 21:21:20 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.
Some people think one-shots are evil, but I like them.

The supply to delay variation in the Greenpak SPLD 16 bit counter
configured as a one-shot is around 10, in simulation anyway..

I'll try to measure it this weekend, I'm interested to see. What general
length of one-shot are we talking?

In one application, just a few nanoseconds. I figured that I could run
\Q to \Reset through a gate or two.

I would use the D input of the flop for "pulse picking".

bitrex

2024-07-12 16:27:21 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.
Some people think one-shots are evil, but I like them.

The supply to delay variation in the Greenpak SPLD 16 bit counter
configured as a one-shot is around 10, in simulation anyway..

I'll try to measure it this weekend, I'm interested to see. What general
length of one-shot are we talking?

In one application, just a few nanoseconds. I figured that I could run
\Q to \Reset through a gate or two.
I would use the D input of the flop for "pulse picking".

Yeah that's tough cuz even at 50 MHz 1 clock is 20 ns and at low counts
there's also a variable offset a la:

pulse length = [(Counter data + 1) / CLK input frequency – Offset],

Where Offset could be in the range 10s of ns at that clock frequency,
worst case, independent of supply

john larkin

2024-07-12 16:36:16 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>

Yikes, 36 years old. CD4000B logic.
I like d-flop one-shots because they are fast, truly edge-triggered, and
can be gated with the D input.
But RC feedback into a reset input is risky at best. Some flops simply
won't work that way... they hang up.

Is this in furtherence of your TDR experimentation? I can't think of
anything else a one-shot is useful for.

Phil is doing a TDR project. I'm mostly doing slow precision stuff
lately.
I am planning a few new products, and one is a sort of precision pulse
generator. I was thinking to have the "HIT" flop, the first trigger
recognizer, be the one-shot. But it's easier to put that inside an
FPGA. The problem with FPGAs is time jitter, from all the routing
crosstalk and clock feedthru and ground bounce and power supply
sensitivity. Maybe they can be managed.
I tested one Xilinx chip for pin-to-pin delay sensitivity vs core
supply voltage. It measured 70 microvolts per picosecond.
Some people think one-shots are evil, but I like them.

The supply to delay variation in the Greenpak SPLD 16 bit counter
configured as a one-shot is around 10, in simulation anyway..

I'll try to measure it this weekend, I'm interested to see. What general
length of one-shot are we talking?

In one application, just a few nanoseconds. I figured that I could run
\Q to \Reset through a gate or two.
I would use the D input of the flop for "pulse picking".

Yeah that's tough cuz even at 50 MHz 1 clock is 20 ns and at low counts
pulse length = [(Counter data + 1) / CLK input frequency Offset],
Where Offset could be in the range 10s of ns at that clock frequency,
worst case, independent of supply

A 1 ns Tiny flop and a 1 ns gate (or even a PCB delay line) would make
a gated one-shot that would run at a couple hundred MHz.

Connecting \Q directly to \R would be interesting. I should try that.
The 1 ns cmos flop is NC7SV74.

bitrex

2024-07-13 01:08:08 UTC

Post by john larkin
On Wed, 10 Jul 2024 22:50:54 -0000 (UTC), Cursitor Doom

If you google use d-flop as one-shot
you get some remarkably silly circuits. Many just swipe from this
http://www.discovercircuits.com/DJ-Circuits/oneshots.htm

<https://www.n5dux.com/ham/files/pdf/

Working%20With%20Monostable%20Multivibrators.pdf>