74hct4046a NXP Semiconductors, 74hct4046a Datasheet - Page 26

• Manufacturer Part Number: 74hct4046a
• Description: Phase-locked-loop With Vco
• Manufacturer: NXP Semiconductors

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