AnsweredAssumed Answered

AD8275 Accuracy Problem

Question asked by Adam.Yao on May 6, 2017
Latest reply on Jun 7, 2017 by christoliver

Hi,there

I'm using AD8275 for my project to scale the +/-10V bipolar singal to unioplar 0-4V so that it could be accepted by a 5V ADC. According to the typical appication circuit of the data sheet,i built a minimum one based on this chip.During testing,i found that it worked well for positive signals,but the scaled output was not so accurate as i expected when input was switched to negative range.Can someone help me figure out what the probelem lies in? I attach some measured and calculated value here. 


** The measured reference voltage(VREF) is about 4.1V
** VOUT = VIN / 5 + VREF / 2

 

  VIN     Measured Value     Calculated Value
+9.5V          3.95V                       3.95V
+7.5V          3.55V                       3.55V
+5.0V          3.05V                       3.05V

 

  0.0V          2.05V                        2.05V

 

-5.0V          1.04V                        1.05V
-7.5V          0.54V                        0.55V
-9.5V          0.12V                        0.15V

 

 

It's clear that the accuracy is not satisfied when VIN goes to negative.

 

Thank you in advance.

 

--Adam

Attachments

Outcomes