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From: pda@crystal.UUCP
Newsgroups: net.analog
Subject: Re: Video A/D converters
Message-ID: <465@crystal.UUCP>
Date: Wed, 29-May-85 16:14:58 EDT
Article-I.D.: crystal.465
Posted: Wed May 29 16:14:58 1985
Date-Received: Fri, 31-May-85 04:29:57 EDT
References: <127@uvicctr.UUCP>
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Organization: U of Wisconsin CS Dept
Lines: 39

> I have a need for a very fast A/D converter.
> 
> SPECS:
> 	4MHz conversion rate
> 	4 bits resolution
> 	binary output
> 
> I realize that this can be done with discrete comparators, etc.
> and this is how I am doing it at the moment,  but I want more
> convenience and a lower package count.  I also know about the
> RCA CA3300 but this seems to be unavailable for the near future.
> 
> Anyone have any tips?
> 
> -- 
> 		Doug Collinge
> 		School of Music, University of Victoria,
> 		PO Box 1700, Victoria, B.C.,
> 		Canada,  V8W 2Y2  
> 		decvax!nrl-css!uvicctr!collinge
> 		decvax!uw-beaver!uvicctr!collinge
> 		ubc-vision!uvicctr!collinge


Look into flash encoders.  They come in several speeds and resolutions.
4 Mhz would easily be found.  There are some up to 100mhz with resolutions
up to 8 bits. RCA, TRW and Siemens make a variety of different configurations.

A flash encoder is in effect a stack of 2**n comparators with a laser trimmed
resistor network for the reference voltage at each comparator.  The physical
layout of the board around these devices is critical for good performance. They
have a tremendous bandwidth and are integrating digital and analog electronics
on one board.  Watch out for noise to couple through the board grounds and many
other places.

	Paul Anderson
	University of Wisconsin
	Computer Sciences Dept.
	Madison, Wis 53706