1ns max jitter oscillator, cheap - for fast 4 diode sampler

LC beats RC

the

chips if it is not necessary,

Can you see phase noise with a DSO by triggering on the oscillator and then looking at the signal a long time later. And seeing how stable it is wrt time.?

George H.

Excellent. Thanks

The Pepper thing, where an analog ramp is suspended for some number of XO clocks, is magnificent. EG&G used to sell a DDG based on that. Theirs was a very bad implementation of a great idea, and the interrupted ramp thing has drift problems for long delays.

Any more information? All I get is Dr. Pepper and pepper spray.

Any more info? All I get is Dr. pepper and pepper spray

It's referenced in the Wiki article, patent US4968907A. The patent is hard to read, but basically he built a constant-current, linear analog ramp delay generator to cover some modest time span, and suspended the current for some integer number of XO clocks to add time. The async suspensions add time but don't add clock jitter. Brilliant.

I had an understanding to license the patent, but decided to do the triggered oscillator thing instead. It's better for long delays.

Well, couldn't you add a PLL to boost the frequency to what is needed (in my case 144MHz). If the PLL phase noise if good enough that is

Cheers

Klaus

I wasn't able to find the Wiki. Searched it for your name, but nothing popped up.

Cheers

Klaus

Sounds like rapidly entering the territory of "not cheap." :-( but higher-performance Wien bridges are a thing and might be interesting to experiment with

The literature seems to indicate they can't easily hit the phase-noise performance of LC or crystal, but can beat ring oscillators or RC relaxation oscillators.

There are finally only so many fundamental oscillator topologies and variations on a theme; the Wien bridge I think is a gyrator-type where positive feedback is used to boost a low-Q resonator network into simulating a high-Q one.

otally at square one

er. RC typically have 1us of jitter (found info on the web), and a crystal oscillator, standard type probably 1ns jitter. But I think that idea was cr azy, a PLL clean up, would not work I guess.

could do many samples and average), I would guess I need jitter of 300ps (1

with low price in mind)

eflected pulse. Since I need up to 200m lenth, the maximum time from the em itted pulse to reflected is 3us. So if the jitter is slowly changing over t ime, it may be a lot less in only that time span.

In this case I need a fast comparator, sub ns response time. They cost over 2 USD which is a lot more expensive than a picosecond timing PWM microcont roller

Cheers

Klaus

The PLL is the one onchip, inside the microcontroller

This maybe,

GH

Where do you get one? any model numbers?

....

OK. The only one with hard numbers.

-73.7 dBc/Hz at 10 KHz offset from 5.something MHz carrier.

the cheapest 5 MHz XO I could find at Digikey in about 20 seconds:

-145 dBc / Hz at 10 KHz offset, or about 70 dB better. This precision part costs 61.5 cents.

And into that 3.2 * 2.5 mm footprint they won't get much of a quality crystal.

A 5MHz quality crystal would have a Q of > one million. (or abt 100K @ 100 MHz; Q*f is abt. constant for comparable material.)

And the newfangled figure of merit: 172 dB for the Wien bridge oscillator.

For the current crop of Hittite, AD and TI synthesizers with on-chip resonator I remember > 230 dB.

Forcing Wien bridges into the context of "accurate sampling clocks" seems quite far-fetched.

What offchip Ls or crystals do you need for that 61.5 ct. thing?

regards, Gerhard

Thanks. And this thing sells for how much?

Do you have any information on the ultra fast comparators, such as risetime, offset, delay time? There is nothing in the datasheet.

Significantly below 2 USD (I cannot disclose the RFQ I have)

Comparator specs is on pgae 99

Risetime is just an digital IO (5ns)

Cheers

Klaus

Thanks. I was searching for "ultra fast comparator" which is the term in the title. I had no idea they would change the term.