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'[AVR]: Decoupling Aref when using AVcc on ADC'
2003\05\09@110428 by John Pearson

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Refering to the MEGA8 ADC reference voltage, two sources mention decoupling Aref pin with a capacitor when using AVcc as the voltage reference.

I am unable to find what capacitor value or how to install.
So can I assume I use a .1uF mono tant. between AVcc and ground?

Thanks

John

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2003\05\09@111454 by Dave VanHorn

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At 08:17 AM 5/9/2003 -0700, John Pearson wrote:
>Refering to the MEGA8 ADC reference voltage, two sources mention
>decoupling Aref pin with a capacitor when using AVcc as the voltage reference.
>
>I am unable to find what capacitor value or how to install.

That's because it's up to you, and the right answer depends on your system
noise.

>So can I assume I use a .1uF mono tant. between AVcc and ground?

Sure.
I also put a 10 ohm resistor in series with AVCC, and a local bypass there.

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2003\05\09@195006 by John Samperi

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At 08:17 AM 9/05/03 -0700, you wrote:
>Refering to the MEGA8 ADC reference voltage, two sources mention
>decoupling Aref pin with a capacitor when using AVcc as the voltage
reference.
>
>I am unable to find what capacitor value or how to install.
>
>So can I assume I use a .1uF mono tant. between AVcc and ground?

John

The AT90S8535 specs show a 100R in series with AVCC and a 10nF
from AVCC to ground. But as David mentioned you may have to adjust
these to your condition. I'm using the above values in one of my boards.

Regards

John Samperi

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