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From: lbechtle@uceng.UC.EDU (laurie bechtler)
Newsgroups: sci.electronics
Subject: shmoo plots
Message-ID: <7905@uceng.UC.EDU>
Date: 30 Mar 91 04:40:28 GMT
Organization: Univ. of Cincinnati, College of Engg.
Lines: 16

Easy...a shmoo plot is just a graphical representation of some kind
of circuit condition versus two input variables.  When I had a real
job (as opposed to this grad school stuff) it was at a semiconductor
manufacturer and we used them all the time.  There are as many
variations as you have variables.  Example:  make the x-axis the 
supply voltage, and the y-axis the '1' state voltage level.  Pick
an output criterion, say, does the circuit pass some specific functional
test?  Place an X everywhere on the plot that the circuit passes the
test.  You end up with some funny blob shape full of X's that shows
you where (on that particular set of axes) the circuit functions.

I think the name came from the old cartoon Li'l Abner...wasn't there
a creature called a shmoo?  I could be wrong.  Anyway, just take a
close look at the axis labeling and the test criteria for the graph
points.  You can also use more levels of description (0-9, say, or
letters) to mark different levels of performance.