EL4584CN 查看數據表（PDF） - Elantec -> Intersil
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EL4584CN Datasheet PDF : 16 Pages
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EL4584C
Horizontal Genlock 4 FSC
Xtal VCO Component Values (Approximate)
Frequency
(MHz)
R1
(kX)
C1
(pF)
C2
(uF)
13 301
300
15
001
13 5
300
15
001
14 75
300
15
001
17 734
300
15
001
10 738
300
15
001
12 273
300
15
001
14 318
300
15
001
Choosing Loop Filter
Components
The PLL VCO and loop filter can be described
as
Where
Kdephase detector gain in A rad
4584 – 13
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
Colpitts Oscillator
F(s)eloop filter impedance in V A
KVCOeVCO gain in rad s V
Neinternal or external divisor
It can be shown that for the loop filter shown
below
C3
e
KdKVCO
N0n2
C4
e
C3
10
R3
e
2Ng0n
KdKVCO
Where 0n e loop filter bandwidth and g e loop
filter damping factor
1 Kd e 300 mA 2qrad e 4 77e-5A rad for the
EL4584C
4584 – 12
C1 is to adjust the center frequency C2 DC iso-
lates 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
1
Fe
2q0LCT
2 The loop bandwidth should be about H-sync
frequency 20 and the damping ratio should be
1 for optimum performance For our example
0n e 15 734 kHz 20 e 787 Hz 5000 rad S
3 Ne910 from table 1
VCOfrequency 14 31818M
Ne
e
e 910
H-SYNCfrequency 15 73426k
4 KVCO represents how much the VCO frequen-
cy changes for each volt applied at the control
pin It is assumed (but probably isn’t) linear
about the lock point (2 5V) Its value depends
on the VCO configuration and the varactor
CT
e
(C1C2)
a
C1C2CV
(C1CV) a
(C2CV)
10
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