The ADC is operated with an external clock or with the internal oscillator. For external clock operation, apply the clock signal to the CLKIN pin. The ADC detects the presence of the external clock and selects the clock automatically. Read the CLOCK bit in the STATUS0 register to verify the clock mode. As described in Table 9-7, the clock frequency depends on the data rate used. Be sure the external clock is free of overshoot and glitches. A source-termination resistor placed at the clock buffer often helps reduce overshoot.

To operate the ADC by the internal oscillator, connect CLKIN to DGND. Be aware of the accuracy of the internal oscillator as described in the Section 7.5. The internal oscillator begins operating immediately at device power-on.