MkIII RGB/Sync combiner - Which PLL?

[Kat Manton]

Hi,

As I've not worked at the sharp end of hardware design I'm a bit out of touch these days.

The MkIII version of my RGB/Sync combiner is going to use a PLL running at 20.250kHz or thereabouts, locked to the incoming nominally 10.125kHz TTL-level line-sync pulses from the PC. (Eventually with added jumpers/switches/automatic gubbins to handle other standards as well, but I'll deal with 405-line first.)

Armed with the output from this along with the line and field-sync pulses from the PC I should be able to generate much better sync signals than the basic XOR-gate circuit in the MkII produces.

The question's in the title, which PLL? I note the venerable '565 is still available; Farnell list the LM565CN in 14-pin DIL package, RoHS-compliant, for £1.20. I last used this device in a RTTY terminal in 1983; I guess it's been around a while and with a bit of luck might soldier on for a while yet.

I'm inclined to use this one, unless anyone has any better suggestions?

Regards, Kat

[ppppenguin]

I would probably use a 4046. Or an HC4046.

[oldeurope]

Originally Posted by ppppenguin

I would probably use a 4046. Or an HC4046.

Yes, I agree and here you can see an example how it can be used:


https://www.vintage-radio.net/forum/...?t=7795&page=3

#43

Darius

[Paul Stenning]

I think the PLL based mini AM transmitters like the SSTRAN and the Gizmo use the 4046. I believe the HC/HCT ones can go faster than the bog standard 4046.

These have been around for years and will probably be around for a while yet, so they seem to be a good choice.

[ppppenguin]

Originally Posted by Paul Stenning

I believe the HC/HCT ones can go faster than the bog standard 4046.

I have used the HC4046 reliably at 27MHz. Needs to be a Philips part to run at that speed. Motorola and others give up at just over 20MHz.

According to my Philips data the ordinary 4046 (not HC) will typicaly go to 1MHz when run at 5V or 2.7MHz at 15V.

[Kat Manton]

Hi,

Thanks for the input, folks; I think that's settled. 4046 is is

The highest frequency it'll need to run at is 40.950kHz (twice 20.475kHz, the line frequency of 819.) Even if I need this for CBS field-sequential colo(u)r it'd be running at 58.320kHz. All within the spec of the device

Cheers, Kat

[oldeurope]

Originally Posted by Kat Manton

Hi,

Thanks for the input, folks; I think that's settled. 4046 is is

The highest frequency it'll need to run at is 40.950kHz (twice 20.475kHz, the line frequency of 819.) Even if I need this for CBS field-sequential colo(u)r it'd be running at 58.320kHz. All within the spec of the device

Cheers, Kat

Hi Kat,
if you run it at fh x 10 you can get the timing for the H sync and serration pulses with counters. The 4046 has a big frequency range and you need no alignement for the different standarts.

Kind regards,
Darius

[Kat Manton]

Hi Darius,

Yes, that's a good suggestion, thanks. I'm still at the "thinking about how I'm going to do it" stage anyway, no definite plans apart from "I need a PLL locked to line frequency running at some multiple of it."

True to the spirit of 'open-source' this could turn into a community RGB combiner and sync regenerator project

Don't give me too much help with this though, folks; I'm new to a lot of this and there is much fun to be had in working things out myself. But I'll post ideas and scribbled schematics here for comment.

Thanks all for your support and help,

Best regards, Kat