NEC PD17062 - Manual (Page 226)

226
µ
PD17062
18.5.2 Functions of the Phase Comparator (
φ
-DET)
As shown in Fig. 18-5, the phase comparator compares the phase of the output frequency “f N ” of the
programmable divider (PD) and the phase of the reference frequency “f r ”, and outputs the up request signal
(UP) or down request signal (DW).
If the divider output frequency f N is lower than the reference frequency f r , the phase comparator outputs
an up request. If f
N
is higher than f
r
, the phase comparator outputs a down request.
Fig. 18-6 shows the relationship among the reference frequency f r , divider output frequency f N , up request
UP, and down request DW.
In the PLL disable mode, neither up nor down request is output.
The up and down requests are directed to the charge pump and unlock detection block.