NNTP-Posting-Date: Fri, 17 Jan 2003 13:05:58 -0600
Date: Fri, 17 Jan 2003 13:08:58 -0600
From: gary drummond
X-Mailer: Mozilla 4.78 [en] (Win98; U)
Subject: Re: RS-232 controlled video switch
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gary drummond wrote:
> Michael Culley wrote:
> > Gary,
> > Thanks for the reply. I've had a look at the datasheets for these chips and
> > the 4558 looks like what I am after. I've still got a couple of questions.
> > Can I wire the video signal direct to this chip or do I need some external
> > components?
> > Do I need to supply -5V? If I do, how do I get -5V?
> > Thanks again.
> > --
> > Michael Culley
> > "gary drummond" wrote in message
> > news:3E27E37F.2E62BEA0@sbcglobal.net...
> > > Michael Culley wrote:
> > > >
> > > > > There is a Maxum chip specifically for video switching.
> > > > > Little 8 pin DIP does 2 in 1 out.
> > > >
> > > > Do you have a number?
> > > >
> > > > --
> > >
> > > MAX453 2x1
> > > MAX454 4x1
> > > MAX455 8x1
> > > All contain an amp/buffer amp.
> > >
> > > Gary
> You said in your email you had 3 bits for selection, the 4558
> wants more...
> Direct-No, terminate with 75 ohms.
> The 4558 does have the capability of single Vcc (it says), but it
> will be degraded (higher Ron and possible crosstalk).
> Read the Grounding and bypassing section for the things to
> watch out for, and keep them in mind if you try single Vcc, they
> get much more critical, and will cause more crosstalk.
> +/-5V supplies (Linear only) can be had as a wall wart lots of
> places, but you might find +12, +/-5 cheaper at Jameco, or other
> mail order places. Just make sure the current capacity is there,
> and pay attention to the analog VS DC ground notes...
> I must stress that if you can, do it the right way first, and
> save all the headaches and problems you will have trying
> bandaids to fix a circuit that doesn't perform.
> I am not an engineer, and for some things I have to drag out
> the books to learn or "remember" what I was taught many years
> ago. Following the sheets, and asking for help using a
> reference design, or sample design, and trying to comply with
> the notes from the data sheet, will get many more responses
> than a jury-rigged design, and in most cases will work the
> first time!
> Drop a line when you get it working.
Just a note on books. I got Walt Jung's new OpAmp book at one of
AD's seminars. I never made it through the first one! Damn, I can
sure put the hard stuff off...