UG-549
ADuCM310 Hardware Reference Manual
Rev. C | Page 26 of 192
ADC Voltage Reference Selection
The
integrates a low drift, 2.5 V ADC reference source. By default, this internal reference is enabled and selected as the
reference source for the ADC. When using the internal 2.5 V voltage reference, ensure the following:
•
ADCCON[7] = 1 to power up the internal reference buffer
•
AFEREFC[3] = 0 to select the internal reference as the ADC reference source
It is also possible to select an external reference source through the ADC_CAPP pin.
To select an external voltage source as the ADC reference source, ensure the following:
•
ADCCON[7] = 0 to power down the internal reference buffer
•
AFEREFC[3] = 1 to select the external reference as the ADC reference source
The external reference source must be capable of driving the 4.7 µF capacitor on the ADC_CAPP pin.
If switching from the external to internal reference voltage source, note there is a power-on time specification given in the
data
sheet for the ADC reference buffer to fully power up after ADCCON[7] is set to 1.