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From: Fred Bloggs
User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0
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Subject: Re: Design for long interval timer
References: <email@example.com> <firstname.lastname@example.org> <3DEE0CAB.email@example.com>
Date: Wed, 04 Dec 2002 16:29:08 GMT
NNTP-Posting-Date: Wed, 04 Dec 2002 08:29:08 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Winfield Hill wrote:
> Fred Bloggs wrote...
>>Spehro Pefhany wrote:
>>>for a timer.. consider using the MC14541.
>>Hmmm...a few problems with one:
>>1) ON is dropping products left and right;
> The availability of '4541' timer chips is certainly as safe to rely
> on as any IC. It's a popular, venerable design, widely stocked at
> good prices, and manufactured by five companies: Philips, TI, ST,
> Fairchild, and ON Semi. I'd probably buy an ON Semi IC, because
> Motorola originated the design.
>>2) the "exploded logic diagram" is clearly in error regarding the
>>MODE control logic;
> Use another vendor's data sheet if that bothers you. TI's data
> sheet (acquired from Harris = Intersil) has a good description.
> Of course one should always use the data sheet's Truth Table or
> Function table if in any doubt.
Okay- thanks for the advice....
>>3) the AUTO RESET only works for Vdd above 8.5V;
> "The AUTO RESET consumes an appreciable amount of power and should
> not be used if low-power operation is desired." Careful designers
> would consider avoiding use of a 'black-box' reset circuit anyway.
The 8.5V lower limit excludes 5V and this is more often than not a
> The 4541 design has much to recommend it, hence its over 30 years
> of popularity. Most of us have used it successfully for a variety
> of tasks in some of our designs.
I keep hearing that but don't see it. Looks like something with a lot of
unnecessary inputs that largely go unused, at the expense of providing
only a single Q output.
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