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AC Bandgap

 
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jmpe

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Joined: 05 Aug 2007
Posts: 7
Location: Gelsenkirchen

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PostPosted: Mon Jan 24, 2011 3:21 pm    Post subject: AC Bandgap Reply with quote

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)

Greatings
JMPE
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mattcro

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Joined: 03 Oct 2007
Posts: 324
Location: Scotland

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PostPosted: Tue Jan 25, 2011 12:03 pm    Post subject: Reply with quote

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.

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jmpe

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Joined: 05 Aug 2007
Posts: 7
Location: Gelsenkirchen

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PostPosted: Wed Jan 26, 2011 1:33 pm    Post subject: Reply with quote

Hi Mattcro

I thouth so, the same problem as ST. DS are plain translations.
If read too quickly (as I did) you'll conclude it would be possible.

BUT
ATtiny87/167 solves my problem. Seems to be a wonderful IC.
Thanks a lot , till next time

JMPE
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