The soft calibration logic minimizes the DCO fluctuations in the DPLL. During
an initial calibration period, CLKOUT3 is reprogrammed to cover
frequencies spanning the entire DCO frequency range. After calibration completes, the
original CLKOUT3 settings are restored. As the DPLL switches between
settings, the DCO frequencies overlap, and the JUMP values allow the DPLL to switch
between the settings while minimizing DCO fluctuations.
If calibration logic is not used, unexpected behavior can occur, such as the following:
- The DPLL does not guarantee jitter performance without the calibration logic.
- The DPLL can under-report jitter, which can affect STA.
- The DPLL can experience locking issues.