Count 1ns pulse

I have know got a BNC model 555 pulse delay generator and a more powerful scope LECROY 9361C which is more than capable, im going to stretch the 5ns TTL pulse from the pad to 10ns and see if the counter will except this?

"Typical "means that half the IC's the manufacturer produces or - more precisely - half thebatches of chips that the manufacturer produces (since within-batch variation is a lot smaller) won't count reliably at

58MHz.

Use the worst case figures - here 30MHz and 20nsec.

Bear in mind that when you string 74HC4520 synchronous counters together, they lack the terminal carry output and the count-enable inputs available on the 74ACT163 that make it easy to create a wider synchronous counter - see figure 2 in the 163 data sheet.

When working out how fast a wider synchronous counter can go, you have to ignore the maximum clock frequency quoted for a single counter (95MHz), and add the worst case (longest) propagation delay from the the clock to the terminal carry output (11.5nsec with a 5V rail) to the recommended minimum set-up time required for the clock enable inputs before it can be relied on to handle an incominng clock edge correctly (5nsec with a 5V rail), for a total of 16.5nsec, corrrsponding to a maximum count frequency of 60MHz.

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Bill Sloman, Nijmegen

"Paul Taylor" schreef in bericht news:e9ni87$t30$ snipped-for-privacy@cpca14.uea.ac.uk...

Why do you think that your minimum pulse width is 5nsec?

And why would you want to stretch it?

The 74ACT163 has a minimum clock pulse width specification of 3.5nsec with a

5V rail, 4,5nsec with a 3.3V rail, and will count at 41MHz even when assembled into a 12- or 16-bit wide synchronous counter.

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Bill Sloman, Nijmegen

I see that now bill shame they don't do a dual package version of the

74act163? as I need to keep the board as small as possible.

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Why don\'t you get ahold of the guy again and ask him what the width
of the output pulse is?  I\'d almost bet that it\'ll be about half of
the pulse-pair resolution, or about 12ns, which should get you over
the hump.

Just emailed him, mind you when i spoke to him on the phone i explained my problem and mention about stretching the pulses because the counter wasn't recognising them he said it is feasible as they do this also, he even emailed the circuit they use. Anyway lets see what the email brings back.

The output from the pad has a 2ns rise and fall time these are exact pulse every time i made an assumption that in the worst case scenario if the pulse stays on for 1ns then that gives me the 5ns pulse? the reason i was going to stretch the pulse was before you mention about the

74ACT163 which will or should do the trick i haven't got any of these but i do have a 74F163 which will read a 6ns pulse so for now im going to give this ago and order in some of the ACT types, Bill im interested in how exactly you calculate the 41Mhz for future reference.

Thanks

"Paul Taylor" schreef in bericht news:e9o13d$17r$ snipped-for-privacy@cpca14.uea.ac.uk...

The 74ACT163 uses too many pins to allow you to fit two into a 16-pin package.

The 74F579 has tristate outputs, which means that it can fit an 8-bit counter into a 20-pin pacakage. Not quite as fast as the ACT163, and probably eats more current, but it might be interesting, if you can find someone willing to sell you a few. Fairchild will probably send you free samples if you ask nicely, but maybe not enough.

If board space really is a problem, go for a biggish programmable logic device. My guess is that the smallest of the CoolRunner 2 IC's, with 32 logic cells could accomodate two 12-bit synchronous counters and most of the rest of your glue logic in a single 44-pin package

If you went for the next step up, with 64 logic cells in the same package, you could probably accomodate all the logic on the board ...

And I'm pretty sure that the parts are fast enough to make your counter ...

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Bill Sloman, Nijmegen

"Phil Allison" schreef in bericht news: snipped-for-privacy@individual.net...

He isn't the first. It took a while before I started performing to my potential. It looks as if he can learn, which is more than can be said for some around here.

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Bill Sloman, Nijmegen

"Paul Taylor" schreef in bericht news:e9o3r9$9$ snipped-for-privacy@cpca14.uea.ac.uk...

What sort of photomultiplier tube are you using to drive the AD7 amplifier discriminator?

Photomultiplier data sheets usually list the typical single photon output pulse width - it depends on the spread of the electron trajectories through the dynode chain, and it is pretty reproducible.

Using the wrong voltage distribution down the dynodes can mess up the pulse width - with fast focussed high gain tubes yo can need a lot of voltage across the last few dynode to prevent the space chage associated with the electrons from messing up the electric field and spreading out the electrons.

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Bill Sloman, Nijmegen

"Bill Slowman Autistic Cunt "

** Asinine...........

** Wot - as the biggest faker out ???

LOL ....

** Looks to whom ??????????

Only to a criminal pile of autism f***ed wog shit.

......... Phil

"Bill Slowman Autistic Cunt "

** Geeez, you do like *sucking* this f****it pommy charlatan's tiny c*ck in public.

Don't ya - Billy boy ??

Says it all about where YOU are coming from.

....... Phil

Here you go, Phillys:

Item 34923 is one toy you won't wear out. Not only that, but you won't run out of batteries. Buy it and a step down transformer, use it on yourself and STFU. The sailors and drunks will thank you.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

We have to be kind to Phil. He lives in Sydney, and can't get refugee status anywhere else.

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Bill Sloman, Nijmegen

Don't be a bigger idiot than you have to be.

I spent a couple of years working on single photon counting electronics and I've got two papers in the Journal of Physics E: Scientific Instruments covering aspects of that work.

The electronics is much the same as we used in the version of the Everhart-Thornley secondary electron detector we developed for the Cambrdige Instruments Electron Beam Tester in 1989-91.

In short, I'm advertising my expertise (such as it is) and cultivating potential customers - knowing full well that the University of East Anglia doesn't have any money, and would spend it on hiring more graduate students if they did.

Or are you just generalising your own obvious enthusiasm for verbal abuse to include oral abuse as well?

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Bill Sloman, Nijmegen

He'll burst a vessel if he keeps on like that!!!!!

All the gear - no idea!!!

The problem is not misreading the scope, but failure to sanity check the reading.

You need to develop a sense of "that (probably) can't be right" based on knowledge of what might reasonably be happening.

Yep, poor sod, but he has come to the right place, wonder if Paul has a copy of AoE?

martin