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ADC Accuracy Improvement

Question asked by Kavitha Kakarla on Aug 6, 2017
Latest reply on Aug 7, 2017 by Markus Ransberger

Hi,

We are using MPC5746C micro for one of our projects and we observed below issue for our ADC Module:

 

We are providing 5V reference voltage to our custom board, but because of the Resistors used in the Voltage Divider Circuits at the Regulator Output, we are observing slightly higher voltage which is approximately 5.04V (which is unavoidable).

So, when we try to convert the ADC Count observed in the CDATA field of ADC_0.CDR register to Voltage value, around 20-50mV higher voltage is observed compared to the ADC Input voltage.

 

To resolve this issue, any suggestions on the below points:

 

1. We are following the ADC Calibration Process as mentioned in the MPC5746C reference manual section      34.6.11.1. Apart from this was there any other procedure to be followed to ensure ADC is properly calibrated?

 

2. As mentioned above, due to the slight change in the reference voltage, we are receiving different ADC Output    value from the applied input voltage

 As per the MPC5748G reference manual, in case of any board issues, can we use the ADC0_OFSGNUSR        register to eliminate the slight difference in the ADC Output value OR is there any other method that can be  suggested to resolve this issue?

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