THE 555 TIMER IC

An Interview with Hans Camenzind

 

Oral History – Hans Camenzind

Continued)

 

You mentioned the term “rubylith” as required in the IC design process. How was that used? 

There was an Exacto knife attached to a parallel arm.  You used this to cut out the “runs”  (in the rubylith),  and peel off very carefully the plastic material from the area that’s not supposed to be there.  Next, you photograph that, reduce it in size. The rubylith mask is about 300X.   You had a table that was calibrated in hundredths of millimeters, still, it was almost impossible -  if you had two resistors that had to match, to make them absolutely identical. It depends on how much patience you had with that arm.

 

Nowadays, you do it on the computer.  It is a mathematical abstraction, and it’s absolutely accurate.  A resistor is five micrometers wide and that means 5.00000.  And the second one is exactly the same, and the accuracy only depends on an apparatus that takes this number and converts it into a position and shines light on a mask.  The biggest step today, if I designed a new circuit the size of the 555, the design would be about three weeks. I would not breadboard it – I’d simulate it on a computer, and while doing that, I can put in all the variations of the components (its called a Monte Carlo analysis), and they appear in random combinations, and I can be absolutely sure I’ve included all the production variations. So that’s number one. 

 

 

 

 

 

Oral History – Hans Camenzind

(Continued)

 

Number two, I can compare the circuit diagram with the layout (the layout of course is done on the computer too), and be 100% certain it is correct.  There are no mistakes. I’ve never seen a human being that can do that.  It really takes a computer. 

 

So, if you used these modern tools now, how long would the 555 work take?

(In addition to the three weeks design we just discussed), the layout would take about two days.  And then you have to wait.  Some companies can make a prototype in four weeks, and some can take six months. It depends on how busy they are.  I have moved integrated circuits into production from start to finish, from the day I got the contract to the day we had 100 pieces, in six weeks. It can be done.

 

What a change in 30 years! 

Yes, and during that time designing ICs has become much more pleasant.  I mean it is really a pleasure to design an IC today.  It was a pain in the neck back then (it was interesting and challenging), but I remember the days, bent over a light table, checking until you had a backache – it was very laborious. 

 

 

 

 

 

Go To Camenzind Oral History,Page 9

 

 

 

 

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