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AD8436 DC-coupled input

Question asked by Dicky on Oct 23, 2013
Latest reply on Oct 29, 2013 by Dicky



I am using AD8436 to measure either AC or bipolar DC current. The current sensing element is hall sensor. the hall sensor is powered by 0-5V supply. The AD8436 is also powered by 0-5V supply. The offset for the hall sensor output is half of the supply (2.5V). Some questions that i have:


(1) Does AD8436 use half supply voltage as zero output reference? I found input level that results in zero output is not exactly half the supply voltage. For example, i have to input 2.493V instead of 2.5V to get 0V at the output (i am using the input and output buffer of AD8436).


(2) There is 7mV offset between hall sensor zero output and AD8436 zero input. I found that this offset affect low level input signal worse than high level input (please refer to the file attached). Can this be compensated by multi-point calibration method (to be performed with the same calibration for non-linearity effect)?


(3) Is there any other concern that should be taken care of when configuring AD8436 for DC-coupled input?the data sheet mostly describes AC-coupled mode of operation.