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RMS to DC AD8436 dynamic range vs Supply voltage

Question asked by Dicky on Oct 8, 2013
Latest reply on Oct 9, 2013 by krisf

Hi,

 

I am using AD8436 to measure RMS value of AC/DC current. The current is sensed by a hall sensor. The output of the hall sensor has an offset at 2.5V, the range is 0.5-4.5V.

 

The configuration of ADC8436:

(1) DC coupled.

(2) VDD = 5V, VEE = 0V.

 

When i tested the circuit by supplying sinusoidal signal (offset at 2.5V), I got the correct RMS voltage at the output only if the input peak-to-peak voltage is lower than 500mV. When i increased the input signal amplitude, the RMS voltage is not accurate any more.

 

Is this problem due to too low supply voltage? There is no clear specification on the data sheet on the relation between supply voltage and dynamic range. Please advise.

 

Thanks.

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