[Gta04-owner] GTA04 capacitor selection

Dr. H. Nikolaus Schaller hns at goldelico.com
Mon Jan 24 09:19:03 CET 2011


Hi Glenn,
it is our intention to fulfill wishes even before they are spoken out :)

Therefore, the GTA04 design uses 100% ceramic capacitors...

Even the backup battery for the RTC is changed to be a Supercap
and no longer the problematic LiIon button cell we all know from
the GTA02 board.

The only drawback is that it has a much lower capacity than
the battery (60mF vs. ~0,3mAh at 3V) but still sufficient to
swap the main battery without loosing the time.

A LiIon backup battery is problematic for several reasons:
1. models that are reflow solderable are rare
2. LiIon batteries need special care and labeling in Air Freight
3. The battery may be discharged when cleaning the soldered board
4. limited lifetime
5. it is impossible to buy the old Freerunner battery in Europe
    (although it is in production) because no distributor wants to
    take care of the Air Freight issues.

Best regards,
Nikolaus

Am 24.01.2011 um 05:50 schrieb Glenn:

> Another suggestion regarding capacitor selection.
> 
> As far as I know, aluminium capacitor have relatively short lifetimes, are more error prone - they dry out over time, and in the same proces get bigger ESR. I have encountered capacitors in linear power supplies, that failed after 1,5 years use.
> 
> -
> 
> Therefore it is suggested that ceramic capacitors are selected instead - bonus - they are bipolar and they are smaller!



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