weak crystal driving mode (was: Re: [avr-chat] (no subject))

[Clemens Koller]

David VanHorn schrieb:
> > I don't know how the internal osc. behaves. But external
> > crystals can be weakly driven for low power applications.
> > I.e. I have an 3.3V AVR and an external 11.0592MHz crystal.
> > The voltage swing on this crystal has only 1Vss but is still
> > working very reliable (verified with additional load).
>
> Check your CKOPT fuse. You should not run with that fuse in the
> default state without a lot of research as to wether your crystal will
> work on that drive.

As I said, I verified that it works reliable, so I can recommend
using that feature _if_done_right_ to save power, since the
internal oscillator isn't really precise, even if calibrated
(and it still depends on temperature).

> In the default state, the Vittoz oscillator is enabled, which is weak
> and can cause BIG problems.

Which problems? I don't see any problems mentioned in the Errata Sheet(s).
Of course, you mustn't drive any other or any big load with the oscillator
and have a low power (uWatt) capable crystal.
(BTW: I'm using the ATMega168 right now).

Regards,
--
Clemens Koller
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