🚀 go-pugleaf

flux@sys6626.bison.mb.ca (John Kamchen) writes:

> I'm having a problem with a circuit I'm trying to build.
> What I need is a 14Mhz clock that doesn't jitter the length of a video 
> line.  
> An LM1881 provides the syncs, and the clock should be stable as possible.
> Looks like this
> --____----------------------------------------------
> _-____-_-_-_-_-_-_-_-_-_-_-_-  and so on  this is the 14Mhz clock
>  
> I suppose what I'm trying to do is simulate a color-burst sync circuit
> (but using a 14Mhz clock).  The goal is to enable me to address
> a pixel every 70ns (for video sampling, image manipulation & such).
>  
> Anyone know what I can do ?  I've tried Xtals & inverters, all I could 
> think of.  I did get this working using a 74HC4046 PLL chip, but
> the cost was high ($2.50 for the chip), and at the end of the video line, 
> the clock wasn't too stable.
> 
> So, that's what I need.  Need help!
> -John
> SSE BBS (204)589-1078 v32bis AmiTronics- MEGS of 'em

THIS IS A JOB FOR AN XTAL PLL, although I have made it work using XTAL 
INJECTION LOCKED OSCILATORS.
Since you want to ADDRESS each pixel, why not use a standard DIVIDE-BY-N
PLL, so the the COUNTERS become your PIXEL ADDRESSES...

Use any design for the Divide by N counter, single chip or cascaded 
binary counters and gates.
If the Xtal OSC and pixel clock are both stable, you may be able to sync 
using a simple Voltage control using VARACTOR or any DIODE to control 
Capacitance, hence frequency and use a digital mixer and filter to 
control the voltage.

Or .. have U tried the ILL approach? (Injection Locked Loop)
Use the Trailing edge of Sync to trigger a stable 1 SHOT of approx <30 nS 
and inject it using a small cap into a 14MHz feedback OSCILLATOR.  This 
works by triggering on the Fourier harmonics of the Sync pulse, however 
your Q must be large to be stable (almost any XTAL). Hand tuning is a 
must sine the CAPTURE RANGE will also be small (200 ppm)

I worked on this 11 years ago doing Scrambling research and VBI data 
reception methods for a Wpg ENg consulting Co. for MTS.

Call if U need help.
Tony Stewart/ Unisys Canada  (204)257-9233 All opinions are my own!
                        home   "  253-6959

dino@inqmind.bison.mb.ca
The Inquiring Mind BBS, Winnipeg, Manitoba  204 488-1607