U74HCT7046

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

8 of 16

www.unisonic.com.tw

QW-R502-851.A

coupled to the self-biasing amplifier at pin 14. Capacitive coupling is required for signals with smaller swings.

Phase comparator 1 (PC1)

This is an EXCLUSIVE-OR network. To obtain the maximum locking range, the signal and comparator input

)

(

V

V

COMPIN

SIGIN

DEMOUT

CC

φ

φ

π

−

=

The phase comparator gain is:

)

r

V /

(

V

K

CC

P

π

=

As shown in Fig.1, the average output voltage from PC1, fed to the VCO input via the low-pass filter and seen at

π

Fig.1 Phase comparator 1: average output voltage versus input phase difference.

GND

locked if it was initially in lock. The capture range is smaller or equal to the lock range.

With PC1, the low-pass filter characteristics determine the capture range which can be made as large as the

lock range.

This configuration retains lock even with very noisy input signals. Typical behavior of this type of phase