If you are using an external reference or one of the internal
references for the positive reference, then a 5-10uF capacitor
is required on pin VeREF+ or VREF+. If you are using an external
reference for the negative reference, then a 5-10uF capacitor is
required on pin VREF-/VeREF-. However, if you use AVCC as the
positive reference, then no capacitor is required on pin VREF+
or VeREF+ and if you use AVSS as the negative reference, then no
capacitor is required on pin VREF-/VeREF-. When using the AVcc
and AVss as references the power supply decoupling capacitor
provides the necessary low impedance path. Please refer the ADC12
Grounding and Noise Considerations section under the ADC12 chapter
in the MSP430xxxx User`s guide for more details.
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