SAADC error for gain 1/5, 1/3, 2, 4

[bart]

I was wondering if it was any use to make use of gains 2 and 4, and noticed the errors for those gains are missing in the PS.

So do gains 2 and 4 actually increase the resolution?

And what are the errors for those gains?

[haakonsh]

Hey bart,

I believe the gain error for 2x and 4x is about the same as the rest. Gain is used to control the voltage reference, it does not amplify the measured signal. You use the Vref together with gain and the reference ladder to control the voltage range that you can sample over. 

Cheers,

Håkon.

[bart]

Ok, so for a sort of auto gain function, it does make sense to use gains 2 and 4 as well, nice.

[haakonsh]

It's not auto-anything, it's used to set the desired voltage reference for the ADC (Vref * Gain). 

[bart]

Yes, i get that :) But i was planning to adjust gain based on measured signal. So it's good to know that gain 2 and 4 actually add resolution for small signals.

[haakonsh]

Ahh, now I get it :)