U74HCT7046

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

10 of 16

www.unisonic.com.tw

QW-R502-851.A

PHASE COMPARATORS (Cont.)

Phase comparator 2 (PC2)

This is a positive edge-triggered phase and frequency detector. If the PLL is using the comparator, the loop is

comprised of two D-type flip-flops, control-gating and a 3-state output stage. The circuit function is as an up-down

)

(

4

V

V

COMPIN

SIGIN

DEMOUT

CC

φ

φ

π

−

=

The phase comparator gain is:

)

r

V /

(

4

V

K

CC

P

π

=

π

4

Fig.3 Phase comparator 2: average output voltage versus input phase difference.