ADUM3190WT as isolation amp for voltage measurement

 Hello,

I am using ADUM3190 as isolation amplifier and observing gain variation from 1.9 to 2.8 with input voltage of 0.3V to 1.5V. I have a resistive divider network at the input (total resistance is 3Mohm) and power with 5V for VDD1 and VDD2, both are isolated with each other.  The voltage measurement is from 200V to 1000V.  But as per the datasheet, the gain is between 2.5 to 2.7 for WT/WS devices. The schematic is same as the test circuit provided in the datasheet fig.29 with ROD = 4.7kohm.

In one of the post, it is mention about the limited input impedance of the ADUM3190, but datasheet mentioned as 10nA input bias current, which is good enough for my voltage measurement between 200-1000V

Please help me to understand this behavior and make the device work as per the spec.

Let me know if any more information required. 

Regards,

Anand M

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