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LTC2308 ADC Datasheet clarification

Question asked by m3atwad on Jan 17, 2018
Latest reply on Mar 28, 2018 by Clarence.Mayott

Hello,

I'm using the LTC2308 ADC in a design.  It looks like, from the data sheet, the ADC is biased and works from 0 to 4.096V when the Vref and Vrefcomp pins are ONLY bi-passed.  I'm not using them for an external voltage reference.  I want to use the internal voltage reference.  When I test this in the lab my readings max out at ~2.0V.  So, in other words, when I read from a single ended channel by sending the command 0x900 and the input is 2V I get 0x7FF which I'm assuming is the maximum signed result.  From the datasheet, it looks like the ADC is actually biased with the 4.096 voltage from the amplifier/buffer in the diagram. 

 

Long story short, what voltage is the actual ADC using as a reference if I don't provide an external one?

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