Re: Rechargeable 3v battery details for microcontroller (Can't lose data!)

From: Kevin (spamisannoying_at_sothisis.fake)
Date: 01/18/05 

Date: Mon, 17 Jan 2005 23:36:24 -0400

On Mon, 17 Jan 2005 18:28:34 -0500, Mark Jones <abuse@127.0.0.1>
wrote:

> Hmmm... 10mS is not a long time at all... and the EEPROM has a
>1-million write cycle life... is that not good enough? If not, cycle
>through the EEPROM bytes as they are being written and it could last
>for hundreds of millions of cycles.

Well, I was thinking of the possibility of a power glitch or sag in
which the Vcc to the PIC fails while it is writing EEPROM. If this
happens, then the byte currently being written is now corrupt. Also
I'm guessing it probably isn't good for the EEPROM to have the power
fail while writing (I was thinking that the high voltage needed to
generate the erase voltage is generated by the on-chip charge pump
using Vcc. What happens if Vcc fluctuates or droops while writing?
Does this affect EEPROM reliability in some way or does it just
corrupt the EEPROM byte being written to?)

> Probably for quite awhile, but don't forget about internal
>resistances. The cap would probably go dead on its own accord long
>before a 99.2% sleeping PIC would kill it.

Will add some supercaps to the next parts order - I always wanted to
play around with them anyway ;-)

Kevin.

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