Joined: 05 Aug 2007 Posts: 7 Location: Gelsenkirchen
Posted: Mon Jan 24, 2011 3:21 pm Post subject: AC Bandgap
AC Bandgap ref
The ATtiny25(etc) and ATtiny261(etc) have 3-bits of reference selection. Does anyone know if beside the 1V1 reference for the AC (not ADC), the 2V56 is selectable. This would greatly help me in a dual-slope measurement. (measuring 100pF to 200pF)
You cannot select the 2.56V reference as an input to the comparator (only the 1.1V ref). I think the 2.56V is generated in the ADC circuitry.
However, you could set up the ADC to use internal 2.56V ref with bypass cap on the AREF pin, and connect the comparator to the AREF pin to get a 2.56V reference. Note that the internal reference is not very accurate (1.0 - 1.2V specified for tiny25), but that doesn't matter for this type of measurement. _________________ If all else fails, read the manual. Even better: read the manual before something fails. If you can't find it in the manual, search the forum.
BascomAVR 2.0.8.5
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