AD1835A: DC offset voltage

Document created by analog-archivist Employee on Feb 23, 2016
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I am using the Analog Devices EZ-kit lite 21369 development board which has an
AD1835A codec. The problem is that there seems to be an unwanted DC offset on
the output values from the ADC's in the codec. I therefore wanted to use the
built-in high pass DC blocking filter in the AD1835A. As I understand it from
the datasheet of the AD1835A, the filter is enabled by setting bit 8 of the ADC
Control 1 register. However, when I set this bit, I still get a DC component on
the output of the ADC. Do you have any suggestions to a solution?


The bias voltage that you are seeing on the DACx output pins is normal and will
not be removed by register control. An identical voltage is available on the
FILTR pin (18), also called Vref and Vbias in various places in the Datasheet.
I apologize for the naming confusion. I would recommend that you provide
10uF/0.1uF filtering on the FILTR pin and use this voltage as reference for
your DAC output filter stage, as shown in Figure 19 of the Datasheet.