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Voltage and current errors with ADM1191 @ -10 degC

Question asked by EMSolutions on Jan 14, 2013
Latest reply on Jan 16, 2013 by EMSolutions

I'm using 3 ADM1191 to monitor the voltages and currents on my power amplifier FETs (see below). I've set up the devices to read continously and poll the values. They work as expected, except at about -10 deg C, 2 of the 3 devices sometimes start giving erronous results.

 

At 25 deg C the voltages and currents are:

#1: V = 10.5V,     I = 0.98 A

#2: V = 10.5V,     I = 1.9 A

#3: V = 10.3V,     I = 6.8 A

 

But occasionaly I get the following at about -10 deg C:

#1: V = 26.5V,     I = 1.98 A

#2: V = 26.5V,     I = 4.5 A

#3: V = 10.3V,     I = 7.5 A

 

I can resolve the problem by turning the highside DC switching FETs off then on or by re-initalising the ADM1191. However I would like to try and understand what could be possibly causing this fault. We use these devices succesfully on other units to monitor a +6V rail and haven't encountered any issues. Does anyone have any ideas?

AD1191s.JPG

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