SNAS722A December 2017 – October 2018 LMK61E07
The N divider of the PLL includes fractional compensation and can achieve any fractional denominator (DEN) from 1 to 4,194,303. The integer portion, INT (valid range 1-4095), is the whole part of the N divider value and the fractional portion, NUM / DEN, is the remaining fraction. INT, NUM, and DEN are programmed in R25/R26, R27/R28/R29, and R30/R31/R32, respectively. The total programmed N divider value, N, is determined by: N = INT + NUM / DEN. The output of the N divider sets the PFD frequency to the PLL. The feedback frequency to the PFD must equal the reference path frequency to the PFD for the PLL to lock. In DCXO mode, the NUM registers can be reprogrammed MSB first and LSB last to update the output frequency without glitches or spikes.