74hct9046a NXP Semiconductors, 74hct9046a Datasheet - Page 26

• Manufacturer Part Number: 74hct9046a
• Description: Pll With Bandgap Controlled Vco
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Table 2 Design considerations for VCO section.
2003 Oct 30
VCO frequency
without extra
offset
VCO frequency
with extra offset
PLL conditions
with no signal at
pin SIG_IN
PLL with band gap controlled VCO
Fig.28 Typical power dissipation as a function
P DEM
(W)
SUBJECT
10
10
10
3
4
5
10
of R
s
.
V
4.5 V
5.5 V
CC
=
PC1, PC2
PC1
PC2
PC1, PC2
PC1, PC2
PC1
PC2
COMPARATOR
PHASE
10
2
R (k )
s
VCO frequency characteristic. With R2 =
3 k
shown in Fig.29a. (Due to R1, C1 time constant a small offset remains when
R2 = ).
Selection of R1 and C1. Given f
Fig.31.
Given f
to obtain 2f
VCO frequency characteristic. With R1 and R2 within the ranges
3 k
is as shown in Fig.29b.
Selection of R1, R2 and C1. Given f
R1C1 by using Fig.33.
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
MBD109
10
max
R1
R1
3
and f
off
L
300 k , the characteristics of the VCO operation will be as
300 k
and then use this to calculate f
from the equation f
c
c
offset
26
determine the values of R1 and C1 using Fig.31; use Fig.33
with
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
ranges shown in Table 1.
Table 1 Survey of components.
R1
R2
R1 + R2
C1
with
COMPONENT
R2
DESIGN CONSIDERATION
PC_IN
300 k , the characteristics of the VCO operation
PC_IN
= 90 and V
c
off
, determine the values of R1 and C1 using
= 360 and V
= f
c
c
and f
between 3 k and 300 k
between 3 k and 300 k
parallel value >2.7 k
>40 pF
1.6f
VCO_IN
L
min
and R1 within the range
determine the value of product
L
.
.
VCO_IN
= 0.5V
VALUE
74HCT9046A
= minimum.
CC
Product specification
.