Clock Chip

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Clock Chip

Post by LarryWilliams » Tue Aug 19, 2003 9:15 am

I'm looking for a timekeeping chip (DIP Pkg.) that draws only a few uA of current. These days,
it takes a processor to load 'em up, which I don't wish to use. O.K. - so I figured I could find a parallel data loading "real time clock" and broadside the data in, one word at a time, to initialize it. Don't care about using it as a clock per se, just as an accurate timer. Alternatives? '555 isn't accurate. 38kHz xtal and CMOS osc. with divider string will draw over 100 uA. So far, in a DIP Pkg., parallel load, little current, I have found an NEC uPD4991; however, I think it's obsolete. Anyone know of a source for the NEC or has another idea for a low current clock chip?<p>Thanx in advance.<p>Larry

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Re: Clock Chip

Post by Externet » Tue Aug 19, 2003 11:35 am

Hi Larry.<p>A bunch of deceased/obsolete mainboards at my work place have those Dallas Semiconductor dip ic's that keep time and calendar in pc's.
I know nothing about them, but I believe they have a battery inside and could be useable for your needs.
- Abolish the deciBel ! -

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Re: Clock Chip

Post by Mike » Thu Aug 21, 2003 5:28 am

Larry,<p>If you use resistors with a 1% or less tolerance, and the exact capacitor value needed, a 555 is very stable. If you don't want to fool with the 555, I have the packaging for a MOS/LSI Digital Click/Calander/Timer. Where the part is, I don't know. It was purchased at RadioShack, and the packaging says RS 7001, possibly the part name. It was RadioShack part number 276-1756. I searched for the part, and they didn't have it. I can tell that it is very old. At the time it was bought, it cost $10.95, so now, if you find it, it probably will be more. If you do find it, that should be exactly what you need.<p>Inside the pactaging was a atasheet. The Chip is also called the RS 1758, or the CT 7001. It also offers radio as the alarm.<p>
-Mike<p>[ August 21, 2003: Message edited by: mikea1962375 ]</p>

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Re: Clock Chip

Post by happy » Wed Sep 10, 2003 10:43 pm

Not quite sure what you are planning to do, but here is a non-DIP type chip. TI makes the MSP430 series of chips and have app notes for self calibration and temp compensation. They will run the clock program (800 nA) for over 20 years on a coin lithium battery and cost from 99 cents. For a couple dollars more, the LCD driver is included.

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