Datasheet

1997 Nov 25 26
Philips Semiconductors Product specification
Phase-locked-loop with VCO 74HC/HCT4046A
VCO frequency characteristic
VCO frequency
with extra
offset
PC1, PC2 or PC3 With R1 and R2 within the ranges 3 kΩ<R1 < 300 kΩ,
3kΩ<R2 < 300 kΩ, the characteristics of the VCO operation will be as
shown in Fig.26.
Fig.26 Frequency characteristic of VCO operating with offset:
f
o
= centre frequency; 2f
L
= frequency lock range.
Selection of R1, R2 and C1
PC1, PC2 or PC3 Given f
o
and f
L
, determine the value of product R1C1 by using Fig.31.
Calculate f
off
from the equation f
off
=f
o
1.6f
L
.
Obtain the values of C1 and R2 by using Fig.30.
Calculate the value of R1 from the value of C1 and the product R1C1.
PLL conditions
with no signal at
the SIG
IN
input
PC1 VCO adjusts to f
o
with φ
DEMOUT
=90°and V
VCOIN
= 1/2 V
CC
(see Fig.6).
PC2 VCO adjusts to f
o
with φ
DEMOUT
= −360° and V
VCOIN
= min. (see Fig.8).
PC3 VCO adjusts to f
o
with φ
DEMOUT
= −360° and V
VCOIN
= min. (see Fig.10).
SUBJECT
PHASE
COMPARATOR
DESIGN CONSIDERATIONS