2.1 Oscillator Frequency when using FOSC as Clock Source
Oscillator frequency (FOSC) should be 8 MHz or below when using FOSC as the clock source of the ADC, irrespective of the ADC Clock Divider (ADCLK) value. The ADCRC oscillator source should be used for ADC when the application requires using FOSC to be greater than 8 MHz.