EL4585C
Horizontal Genlock, 8 F
SC
Typical Application
Horizontal genlock provides clock for an analog to digital converter, digitizing analog video.
4585–18
Xtal VCO Component Values (Approximate)
Colpitts Oscillator
Frequency
(MHz)
R1
C1
C2
(kX)
(pF)
(mF)
26.602
27.0
300
300
300
300
300
300
300
15
15
15
15
15
15
15
.001
.001
.001
.001
.001
.001
.001
29.5
35.468
21.476
24.546
28.636
4585–12
C
is to adjust the center frequency, C DC iso-
2
1
lates the control from the oscillator, and V1 is the
primary control device. C should be much larger
than C so that V has maximum modulation
capability. The frequency of oscillation is given
by:
The above oscillators are arranged as Colpitts os-
cillators, and the structure is redrawn here to em-
phasize the split capacitance used in a Colpitts
oscillator. It should be noted that this oscillator
configuration is just one of literally hundreds
possible, and the configuration shown here does
not necessarily represent the best solution for all
applications. Crystal manufacturers are very in-
formative sources on the design and use of oscil-
lators in a wide variety of applications, and the
reader is encouraged to become familiar with
them.
2
V
1
1
e
F
2q LC
0
T
C C C
1 2 V
e
C
T
a
a
(C C )
(C C )
1
(C C )
1 V
2
2 V
9
ELANTEC [ ELANTEC SEMICONDUCTOR ]
