24Hz to 60Hz PLL?

It does have the potentially useful feature that the reference ripple goes away when you're exactly in phase. Might be sort of nice to do the

+- pulse thing with some minimum width value for both pulses, and use a fast RC lowpass plus an analog switch to get rid of the up-down bumps when you're near lock. Maybe use the lock detector to control the switch--keep it closed when you're out of lock, and open it briefly to get rid of the barump-bump when you're in lock.

The problem is always how much extra phase shift you can tolerate inside the loop, and the VCO already contributes 90 degrees, which doesn't help.

A few nasty metastability issues, though--same as using D-flops for mixers in offset loops. I learned my lesson about that in 1982, when I was an astronomer masquerading as an EE.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

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=A0 =A0 =A0 ...Jim Thompson

ges.

If you are going for low noise, you really want the added stage of logic clean up that you get by doing the converting to analog outside the chip.

It really isn't infinite. On the 74HC74 it is less than infinite because the set up time to cause the output to toggle is longer than the setup to cause it to be the same. I don't recall how big the effect is but it is a small nonzero value. Perhaps with a different flip-flop it is greater than infinity and so it averages out.

Also a simple tri-state gate that you only enable while the carry out of the counter chain is true works as a nice sort of phase detector. It is a little like a no dead band version of the 2 flip-flop on in that for most of the cycle, the filter capacitor has no current.

The bang-bang loops that I've done were EclipsLite ECL. The EL51 flop seems to have a little setup/hold hysteresis, roughly 1 picosecond, but that doesn't bother a relatively narrowbend loop, like locking a VCXO to some external reference. It's hard to beat a differential-input flipflop bang-bang detector when you want to hold a couple of picoseconds absolute timing longterm.

Any jitter in the reference or the VCO smears out the transfer function of the bangbang pd, making it effectively finite gain. I do the loop math based on some assumption of some jitter.

John

It has been done already many years ago

ciao Ban

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=A0 =A0 =A0 ...Jim Thompson

ranges.

Yes, you have to do that partly because doing math with infinite values is a lot harder.

In all digital stuff, I have used the change in state of the flip-flop to provide the real part to make the loop stable. Basically what I did was:

INC/DEC ! ----------------! ----- ! ! ----- !AND>----Gain one Signal-----!D Q!----+--+----!D Q! --! --!> ! --!> ! ! ! ----- ! ! Q/!-- ! ! NCO/M-- Clock

The Number Controlled Oscillator is just a divide by N counter where the few bottom bits of N are controlled by the upper bits of another counter that is hooked to the INC/DEC control. The "Gain One" signal causes the NCO to increment by 2 on the next clock cycle. This some of the phase lag making the system stable. Without it the output wobbles either side of the correct value. instead of quickly and randomly jittering. The wobble makes a lot of low frequency noise in the output.

Of course "It has been done already many years ago". I invented dirt. Also much of modern PLL technology. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Come on, Jim. We all know that the dirt was just a byproduct of you doing your designs with chisels, on stone tablets. ;-)

--
Greed is the root of all eBay.

By 1967-68, when I was doing PLL, we already had quadrille pads. However we didn't yet have calculators... except for giant Philco on-desk machines bigger than today's towers ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Wouldn't the purchasing office spring for something like a Friden EC-130? Delay line memory, a sexy CRT display, and only $2200 in 1964 dollars...

I went to a mall in Dothan, Alabama in 1972 or 73 while I was stationed at Ft. Rucker. The mall had two levels. The one at ground level was full, but the underground level only had one store, and all it sold was calculators. I wondered for years how long it lasted. :)

--
Greed is the root of all eBay.

I'm surprised they didn't have "The Scotch Tape Store" or "Spatula City". ;-)

The boards for those were made (and installed) by Philco-Ford, Santa Clara. When I did my short stint at P-F in 1968 (I left Motorola with John Welty), I convinced them to dump it... they were, in essence, shipping $1K with each unit :-(

In August 1968 the politicians who didn't like Welty decided to close that division. The asked me how I'd like to go to Blue Bell. I replied, "How'd you like to kiss my ass?" Really. So I called Walt Seelbach (Mr. MECL) at Motorola and went straight back, to ultimately work on PLL's.

The one and only time I left Arizona :-( ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

No, just $400 to $600 calculators and over 50 storefronts that were still vacant.

--
Greed is the root of all eBay.

AVR? Is that one of the Z80 compatible chips the Chinese use to run MP/3 players, cameras etc? I'd like to see 8 bit CP/M running on one and starting with an MP/3 player with flash memory, USB and an LCD for cheap would make it more interesting.

See the CP/M usenet group.

On a sunny day (Sat, 6 Mar 2010 02:14:21 -0800 (PST)) it happened Greegor wrote in :

You could then run my CP/M clone on it too, if it supports Z80 instructions:

But I do not think AVR knows about LDIR? LD (IX-12), value? hehe

ld

Yes, they are made by Norwegian Chinese and headquartered in San Jose Chinatown. Chinese is a genetic term for hard working technical people.

Good enough to control and power the ASICs.

Can CP/M runs in 4 to 8K RAM? Oh, wait. AVR can't run from RAM.

:

of

ould

My parts came today. I tried my design, and it locks solid on the right frequency finally. The new loop filter is awesome. Kudos to Helmut for his damped loop filter. Also, my NE555 debounce circuit fixed the frequency error problem. Yaaaah!

@Jan I will be trying your design next and see how it compares to mine in lock time.

Thanks All Chris Maness