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AD5242: Over -50% variance in measured resistance

Question asked by haripg on Dec 8, 2014
Latest reply on Jul 28, 2015 by haripg

Hi,

 

I was testing the range of the 1M TSSOP AD5242 IC. I encountered over -50% variance in the measured RDAC values and the nominal values. This was seen over both the RDAC channels of 4 chips (That is a test case of 8 RDACs).  Another observation is that at higher values, the resistance is not stable, but keeps drifting.

 

The circuit consisted only of the AD5242 and no other components. The AD5242 was configured as per the data sheet in rheostat mode, with the wiper tied to the unused terminal A. The resistance was measured between Wiper and Terminal B.

 

I am writing the instructions to the IC through I2C provided by mBED platform. I am able to read back the written data.

 

I am attaching a table of readings for reference:

All Resistance values are in Ohms.

 

Screenshot from 2014-12-09 10:00:12.png

 

Is this expected behavior. Is there any way to fix such erratic values?

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