74HCT9046AN Philips, 74HCT9046AN Datasheet - Page 25

• Manufacturer Part Number: 74HCT9046AN
• Description: PLL with bandgap controlled VCO
• Manufacturer: Philips

Philips Semiconductors
Table 3 Design considerations for VCO section.
1999 Jan 11
VCO frequency without
extra offset
VCO frequency
with extra offset
PLL conditions with no
signal at the SIG
PLL with bandgap controlled VCO
P DEM
(W)
10
10
10
SUBJECT
3
4
5
10
Fig.28 Typical power dissipation.
V
4.5 V
5.5 V
CC
IN
input
=
PC1, PC2
PC1
PC2
PC1, PC2
PC1, PC2
PC1
PC2
COMPARATOR
10
2
PHASE
R (k )
s
MBD109
VCO frequency characteristic
With R2 =
characteristics of the VCO operation will be as shown in Fig.29a.
(Due to R1, C1 time constant a small offset remains when R2 = ).
Selection of R1 and C1
Given f
Given f
Fig.33 to obtain 2f
VCO frequency characteristic
With R1 and R2 within the ranges 3 k
the characteristics of the VCO operation is as shown in Fig.29b.
Selection of R1, R2 and C1
Given f
Calculate f
Obtain the values of C1 and R2 by using Fig.32.
Calculate the value of R1 from the value of C1 and the product R1C1.
VCO adjusts to f
VCO adjusts to f
10
3
c
max
c
, determine the values of R1 and C1 using Fig.31.
and f
off
and f
25
and R1 within the range 3 k
from the equation f
L
determine the value of product R1C1 by using Fig.33.
APPLICATION INFORMATION
This information is a guide for the approximation of values
of external components to be used with the 74HCT9046A
in a phase-locked-loop system.
Values of the selected components should be within the
rages shown in Table 2.
Table 2 Survey of components.
c
R1
R2
R1 + R2
C1
c
offset
determine the values of R1 and C1 using Fig.31; use
with
L
COMPONENT
and then use this to calculate f
with
DESIGN CONSIDERATION
PCIN
PCIN
= 90 and V
off
= 360 and V
= f
c
between 3 k and 300 k
between 3 k and 300 k
parallel value >2.7 k
>40 pF
1.6f
VCOIN
R1
L
R1
.
VCOIN
=
300 k
1
74HCT9046A
300 k , the
min
2
V
VALUE
Product specification
CC
= minimum.
.
.
R2
300 k ,