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MC56F847xx 12bit ADC problem with voltages greater than 3.3V

Question asked by anantha saligram on Dec 20, 2014
Latest reply on Dec 23, 2014 by John Winters

We are using Triggered parallel mode for reading ADC channels in ADCA and ADCB.

We observed that if any one of the ADC channels in ADCA goes more than 3.3V, readings belonging to other channels of ADCA gets affected.  In our case, when ANA2 input was about 3.38Volts, ANA3 readings are always high ( 4095 ).  I reduced ANA2 input voltage to less than 3.25V and ANA3 readings are restored to correct value ( which is 2048 corresponding to 1.65 volts).

Do we have any problem in case ADC input goes in the range of 3.3V to 3.6V? Because even with diode protection we cannot prevent voltage going to these levels in hardware.

please reply

regards

anantha

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