MC14046B
SF
9
out
SOURCE
10
FOLLOWER
VCO
R
in
SF
PCA
14
3
in
EXTERNAL
9
VCO
out
@ FREQUENCY Nf′ = f
PHASE
2 OR 13
4
VCO
@ FREQUENCY f′
LOW−PASS
FILTER
COMPARATOR
PC1
OR
11
12
6
7
out
PCB
CI
CI
B
in
A
PC2
out
R1
R2
CI
EXTERNAL
÷ N
COUNTER
Typical Low−Pass Filters
Typically:
R3
C2
R3
(a)
(a)
6N
max
N
OUTPUT
OUTPUT
R
4
C
+
2
–
INPUT
INPUT
f
2 p D f
2 pf
R3 C2
1
L
R4
C2
Ǹ
2f
C
[
100NDf
p
(R ) 3, 000W) C
+
– R C
4 2
3
2
f
2
max
D f = f
− f
min
max
NOTE: Sometimes R3 is split into two series resistors each R3 ÷ 2. A capacitor C is then placed from the midpoint to ground. The value for
C
C
C
should be such that the corner frequency of this network does not significantly affect W . In Figure B, the ratio of R3 to R4 sets
n
the damping, R4 ^ (0.1)(R3) for optimum results.
LOW−PASS FILTER
Filter A
Filter B
Definitions: N = Total division ratio in feedback loop
K K
K K
f VCO
NC (R ) R )
2 3 4
Kφ = V /π for Phase Comparator 1
f VCO
DD
+ Ǹ
+ Ǹ
w
w
n
n
Kφ = V /4 π for Phase Comparator 2
NR C
3 2
DD
2 p D f
VCO
K
VCO
+
V
DD
– 2 V
Nw
N
n
z +
z + 0.5 w (R C
)
)
n
2 p f
10
3 2
r
2K K
f VCO
K K
f VCO
for a typical design W
^
(at phase detector input)
n
R C S ) 1
ζ ^ 0.707
3 2
1
F(s) +
F(s) +
R C S ) 1
S(R C ) R C ) ) 1
3 2
3 2
4 2
Waveforms
Phase Comparator 1
Phase Comparator 2
V
V
V
V
DD
SS
OH
DD
SS
OH
PCA
PCB
PCA
in
in
in
V
V
PCB
in
V
V
V
V
OL
OL
OH
OH
LD
PC2
PC1
out
V
V
V
V
OL
OL
OH
OH
out
VCO
in
V
V
V
OL
OL
OH
VCO
in
V
OL
Note: for further information, see:
(1) F. Gardner, “Phase−Lock Techniques”, John Wiley and Son, New York, 1966.
(2) G. S. Moschytz, “Miniature RC Filters Using Phase−Locked Loop”, BSTJ, May, 1965.
(3) Garth Nash, “Phase−Lock Loop Design Fundamentals”, AN−535, Motorola Inc.
(4) A. B. Przedpelski, “Phase−Locked Loop Design Articles”, AR254, reprinted by Motorola Inc.
Figure 3. General Phase−Locked Loop Connections and Waveforms
http://onsemi.com
6
ONSEMI [ ONSEMI ]
