pwm ...

[gstopp at fibermux.com]

     Delta-sigma DACs are good for audio, yes, but I gather the original 
     thread is talking about slow-moving (DC) DAC outputs for use as 
     control signals in analog systems. Although I've incorporated 4333's 
     into several of my projects (like bringing out extra outputs from the 
     digital out's on my sampler), I've never tried to bring the master/L/R 
     clocks down to very slow rates. The 4333 datasheet calls out a minimum 
     sample rate of 2 khz, so that rules out one-time DAC updates, right? 
     We'd be forced to chew up CPU overhead to keep the DAC updated more 
     frequently, even more than a mux'ed S/H DAC.
     
     Even if you could shoot a serial data stream into a delta-sigma chip 
     as an asynchronous update, you still need to have the CPU generate at 
     least three parallel synchronized lines of bits. In contrast, an 8-bit 
     CMOS latch with a discrete R-2R ladder acts like a single memory 
     location. Write to it and forget it.
     
     Please let me know if I'm wrong - I've a bunch of these lying around!
     
     Long live Crystal!
     
     - Gene


______________________________ Reply Separator _________________________________
Subject: Re: pwm ...
Author:  Jonathan Mayer <jmayer at crystal.cirrus.com> at ccrelayout
Date:    11/14/96 3:18 PM


On Thu, 14 Nov 1996, Kimmo Koli wrote:
> Well, the linearity and even monotony of a 8-bit D/A-converter is usually 
> very poor. Of cource 8-bit D/A-converters are cheap, but are the cheap 
     
Hey, I know of at least one company that produces some very quiet, very 
linear, fairly inexpensive delta-sigma DACs.  better than 8-bits 
resolution, too. cough cough.
     
(inexpensive == US$1..$3, i think)
     
Jonathan.
Crystal Semiconductor
     
_____________________________________________________________________________ 
Jonathan Mayer         http://www.crystal.com       jmayer at crystal.cirrus.com