Re: Simple crystal (4.43MHz - PAL) oscillator + PLL multiplier circuit wanted. - Article 2026 - go-pugleaf

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Re: Simple crystal (4.43MHz - PAL) oscillator + PLL multiplier circuit wanted.

#2026

From: Frank Raffaeli
Date: Mon, 05 Mar 2007 19:40

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On Mar 5, 3:47 am, Lionel <use...@imagenoir.com> wrote:
> Per the subject line. I want to experiment with direct PAL video
> generation from a microcontroller, with the minimal number of parts.
> I'm thinking that a good starting place might be to use a CPU clock
> that's based on the PAL subcarrier frequency (4.43MHz) multiplied with
> a PLL+VCO+Divider to give me phase reference points, & directly
> generate the composite colour signal via an R2R ladder.
>
> So, some questions:
>
> 1) Is this a reasonable concept? (I'm comfortable with per-cycle level
> timing & coding)
>
> 2) Any tips/suggestions/thoughts as to a better approach?
>
I've generated PAL and NTSC CVBS in a Cyclone II (5K) FPGA, $12.90 in
singles. I load the FPGA with a 0.68 micro. Total parts cost: ~ $16.00
in singles w/ 8-bit DAC, ~ $17.00 for 10-bit DAC. Parts total in the
1000+ would be about $8.00. USB is about 1.50 extra if you need
computer control.

> 3) What's a good (simple, cheap, stable) circuit to oscillate a
> standard 4.43MHz PAL sub-carrier xtal? (Ideally just an inverter or
> two)
>
Do you need genlock? If not, a simple xtal osc at 4x or 8x with
inverter will work fine.
Are you familiar with the PAL color subcarrier phase shift wrt the
field sequence?

Frank Raffaeli
http://www.aomwireless.com/

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Subject: Re: Simple crystal (4.43MHz - PAL) oscillator + PLL multiplier circuit wanted.
Date: 5 Mar 2007 11:40:30 -0800
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