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ADAU1701 Auxiliary ADC resolution

Question asked by renhoek on Jun 29, 2018
Latest reply on Jul 3, 2018 by renhoek



I have a question regarding the resolution of the auxiliary ADC on the ADAU1701 DSP's. According to the Datasheet the ADC has 8 bit resolution with a 3.0V full scale analog input.
My problem is that the ADC works correctly as long as the input voltage is between 0 an 1.5V which gives me up to 0b0111 1111 set bits in the Register Control Window in SigmaStudio (so the step size of about 12mV is OK). But when the ADC input goes above 1.5V and up to 3.0V the seven lower bits remain set and the eight bit never gets set.
I have experienced this behavior on all 4 channels and an multiple DSPs.
Am I doing something wrong, or has the ADAU1701 only 7 bit resolution?