High speed ASM-1 VCO question

[Don Tillman]

   Date: Thu, 01 May 1997 14:52:49 -0700
   From: John Speth <johns at oei.com>

   I am experimenting with the ASM-1 VCO trying to get it run cleanly at about
   100KHz.  I was wondering if you anybody could shed some light on some of
   design choices that were made in the circuit.  I understand how it works
   but need info on the more practical aspects.

   My goal is to make a CVable duty cycle modulator for a time-multiplexed
   panner using analog switches.  I figure I would use the ASM-1 core sawtooth
   generator (a standard Electronotes VCO isn't it?) to provide a ramp and an
   LM311 to make a CVable duty cycle convertor.  Problems I have seen is
   excessive ringing (about 10% of signal) in the sawtooth at the end of
   retrace and an LM311 problem (see below).

Umm, I'm confused.  Are you saying that you're planning on using an
especially-optimized-for-accurate-tracking VCO for a fixed frequency
source?  Why are you using a sawtooth wave for PWM instead of the
usual triangle wave?  What are the goals of the circuit? 

  -- Don