MSP430F427A SD16 ADC sampling issue

Abacus Electronics

Other Parts Discussed in Thread: MSP430F427A

I am using MSP430F427A with SD16 ADC for single phase energy meter application.

When I set the SD16 for higher sampling rate (4Mhz) then the sample values gradually decrease even if the input is kept unchanged, and sets down after few minutes to a constant value. But if I decrease the sampling rate (to say 1MHz), the sample values are stable.

I am new to the MSP430 world, please suggest any solution.

Thanks in advance.

over 7 years ago

0 Dennis Eichmann over 7 years ago

Guru 74080 points

Hi Abacus!

Could you describe your hardware around the ADC pin? Possible that the source (the signal you are sampling) has a too high output impedance. Remember that the ADC sinks current with every sample it takes. For example when having a RC circuit in front of the ADC input and the resistor value is too high, the ADC will discharge the capacitor while it is sampling and the too high resistance cannot offer enough current to recharge the capacitor to it's original value in between the samples. Therefore it will loose charge and the voltage drops. This effect decreases with lower sampling rate, of course.

Dennis