[time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

Since we don’t often *need* the smallest cell made *and* we’re probably 
talking lifetime of the cell….. does 22 na vs 33 na matter?

…. hmmm ….

CR2032 ( which is the smallest I would use) is rated at 0.22 AH. 

A nano amp for a year is about 8 uA hours a year. 

So 30 na for 20 years is 0.005 AH 

Indeed, the self discharge of the cell (or life or whatever you want to call it)
will probably get you before the 30 na drain will. 

Based on the previous data on the chip, I think I would just run the crystal
all the time. 

Bob

> On Mar 6, 2018, at 11:22 PM, Mark Sims <holrum at hotmail.com> wrote:
> 
> Probably 20+ years for a lithium coin cell... basically the shelf life of the cell.  I have a card of 24 year old CR-2032's that are still above 3V, and no sign of leakage.
> 
> BTW, never handle a coin cell (particularly in watch applications) with your fingers... your grubby fingerprints are rather conductive and can discharge a cell surprisingly quickly.   
> 
> Also note the clock chip has 512 bytes of RAM in it.
> 
> ----------------
> 
>> Assuming you are going to run it off a battery. What’s the self discharge
> rate on a reasonable battery? 
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