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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Dallas RTC osc stability
Date: Wed, 09 Oct 2002 07:25:04 GMT
NNTP-Posting-Date: Wed, 09 Oct 2002 00:25:04 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
"R. Lewis" wrote:
> Some time ago there was reference to a problem with the osc. on one
> particular Dallas 'real time clock' device.
> I am now looking (again) at their devices but do not want to select a wrong
> un and would appreciate a repeat of that distant post if anyone knows.
I strongly suggest that you do *not* use Dallas RTCs.
Dallas refuses to honour their "guarantee" if one goes bad.
And replacements are not easy to get.
The idea of encapsulating a battery inside epoxy or molded plastic is
not exactly the swiftest in the world; the heat alone degrades the
reliability and life of the battery.
As far as accuracy (and i presume stability) goes, the majority of
crystals made for CPU work have a lousy rating; most are 100 PPM. There
are analog watches (since railroad watches) that do better.
Use an external battery ("coin" lithium) and external crystal
(selected for better accuracy) with a RTC type IC that requires these
Yes, it may cost more in $ and space, BUT the result can be superior
for a user than anything i have seen in a PC.
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