EL4585CN Ver la hoja de datos (PDF) - Elantec -> Intersil
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EL4585CN Datasheet PDF : 16 Pages
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EL4585C
Horizontal Genlock 8 FSC
Applications Information
Choosing External Components
1 To choose LC VCO components first pick the
desired operating frequency For our example
we will use 28 636MHz with an H-sync fre-
quency of 15 734kHz
2 Choose a reasonable inductor value (1-5mH
works well) We choose 3 3mH
3 Calculate CT needed to produce FOSC
1
FOSC e 2q 0LCT
1
1
CT
e
e
4q2F2L
4q2(28
636e6)2(3
3e
b
e9
6)
4pF
4 From the varactor data sheet find CV 2 5V
the desired lock voltage CVe23pF for our
SMV1204-12 for example
5 C2 should be about 10CV so we choose
C2e220pF for our example
6 Calculate C1 Since
CT
e
(C1C2)
a
C1C2CV
(C1CV) a
(C2CV)
then
C1
e
(C2Cv)
b
C2CTCV
(C2CT) b
(CTCV)
For our example C1e17pF (A trim cap may be
used for fine tuning ) Examples for each frequen-
cy using the internal divider follow
Typical LC VCO
4585 – 10
LC VCO Component Values (Approximate)
Frequency
(MHz)
L1
(mH)
C1
(pF)
C2
(pF)
26 602
33
22
220
27 0
33
21
220
29 5
27
22
220
35 468
22
16
220
21 476
47
26
220
24 546
39
22
220
28 636
33
17
220
Note Use shielded inductors for optimum performance
Typical Xtal VCO
4585 – 11
8
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