Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker!ai-lab!mikec
From: mikec@wheaties.ai.mit.edu (Mike E. Ciholas)
Newsgroups: comp.sys.mac.hardware
Subject: Re: SID analog to digital conversion error
Message-ID: <8278@wheat-chex.ai.mit.edu>
Date: 4 May 90 16:35:19 GMT
References: <20509@netnews.upenn.edu> <11220003@hpccc.HP.COM> <8222@rice-chex.ai.mit.edu>
Reply-To: mikec@wheat-chex.ai.mit.edu (Mike E. Ciholas)
Organization: MIT Artificial Intelligence Laboratory
Lines: 27

In article <8222@rice-chex.ai.mit.edu> mikec@rice-chex.ai.mit.edu (Mike E. Ciholas) writes:
>In article <11220003@hpccc.HP.COM> wille@hpccc.HP.COM (Ross Wille) writes:
>>Shouldn't the A/D converter have a sample & hold in front of it?  Since
>>it is using successive approximation, the input should be stable during
>>the entire conversion time.  Maybe the A/D has a built-in S&H but I'd
>>think not.  Maybe it just works well enough with out one.  Anybody know?
>>
>>-Ross
>The ADC0831 has a sample and hold on it, when the conversion start pulse
>comes, it samples for one high period of the conversion clock, then
>ignores the input.  Very nice chip, all in all.
>
>Mike Ciholas

WHOOOPS!  Sorry about that, I am wrong.  The NATIONAL ADC 0831 has no sample
and hold, which is bad.  HOWEVER, MICRO-LINEAR's ML2281 does have a sample and
hold that works as described.  That is where I got the info.  (the micro linear
chip is pin and functional compatible, but offers a sample and hold and faster
conversion timing).  I'll see what I can get the chips for.  If they don't
cost much if any more than the national, then I'll get those for the kits.

Mike Ciholas

email:  mikec@ai.mit.edu
snail:  289 Highland Ave, #108/Somerville, MA 02144
phone:  (617) 623-3563 
air:    N1909C, 1954 Cessna 170B