EL4584 View Datasheet(PDF) - Intersil
Part Name
Description
Manufacturer
EL4584 Datasheet PDF : 12 Pages
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EL4584
For our example, C1 = 14pF. (A trim cap may be used for
fine tuning.) Examples for each frequency using the internal
divider follow.
Typical Application
Horizontal genlock provides clock for an analog to digital
converter, digitizing analog video.
XTAL VCO COMPONENT VALUES (APPROXIMATE)
FREQUENCY
R1
C1
C2
(MHz)
(kΩ)
(pF)
(µF)
13.301
300
15
0.001
13.5
300
15
0.001
14.75
300
15
0.001
17.734
300
15
0.001
10.738
300
15
0.001
12.273
300
15
0.001
14.318
300
15
0.001
The above oscillators are arranged as Colpitts oscillators,
and the structure is redrawn here to emphasize 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 informative
sources on the design and use of oscillators in a wide variety
of applications, and the reader is encouraged to become
familiar with them.
FIGURE 4. TYPICAL LC VCO
LC VCO COMPONENT VALUES (APPROXIMATE) (NOTE)
FREQUENCY
L1
C1
C2
(MHZ)
(µH)
(pF)
(pF)
13.301
15
18
220
13.5
15
17
220
14.75
12
18
220
17.734
12
10
220
10.738
22
20
220
12.273
18
17
220
14.318
15
14
220
NOTE: Use shielded inductors for optimum performance.
FIGURE 6. COLPITTS OSCILLATOR
C1 is to adjust the center frequency, C2 DC isolates the
control from the oscillator, and V1 is the primary control
device. C2 should be much larger than CV so that V1 has
maximum modulation capability. The frequency of oscillation
is given by:
F = ------------1--------------
12π LCT
CT
=
--------------------------C----1----C----2----C----V----------------------------
(C1C2) + (C1CV) + (C2CV)
Choosing Loop Filter Components
The PLL, VCO, and loop filter can be described as:
FIGURE 5. TYPICAL XTAL VCO
9
FN7174.2
July 25, 2005
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