EL4584C View Datasheet(PDF) - Elantec -> Intersil
Part Name
Description
Manufacturer
EL4584C Datasheet PDF : 16 Pages
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EL4584C
Horizontal Genlock 4 FSC
transfer function CveF(VC) where VC is the
reverse bias control voltage and CV is varactor
capacitance Since F(VC) is nonlinear it is
probably best to build the VCO and measure
KVCO about 2 5V The results of one such mea-
surement are shown below The slope of the
curve is determined by linear regression tech-
niques and equals KVCO For our example
KVCO e 6 05 Mrad S V
FOSC vs VC LC VCO
Lock Time
Let SeR3C3 As T increases damping increases
but so does lock time Decreasing T decreases
damping and speeds up loop response but in-
creases overshoot and thus increases the number
of hunting oscillations before lock Critical damp-
ing (ge1) occurs at minimum lock time Because
decreased damping also decreases loop stability
it is sometimes desirable to design slightly over-
damped (gl1) trading lock time for increased
stability
Typical Loop Filter
4584 – 14
5 Now we can solve for C3 C4 and R3
C3
e
KdKVCO
N02n
e
(4
77e b 5)(6 05e6)
(910)(5000)2
e
0
01
mF
C4
e
C3
10
e
0
001
mF
R3
e
2Ng0n
KdKVCO
e
(2)(910)(1)(5000)
(4 77e b 5)(6 05e6)
e
31
5
kX
We choose R3 e 30 kX for convenience
6 Notice R2 has little effect on the loop filter de-
sign R2 should be large around 100k and can
be adjusted to compensate for any static phase
error Ti at lock but if made too large will
slow loop response If R2 is made smaller Ti
(see timing diagrams) increases and if R2 in-
creases Ti decreases For LDET to be low at
l l lock Ti k 50 ns C4 is used mainly to attenu-
ate high frequency noise from the charge
pump
4584 – 16
LC Loop Filter Components (Approximate)
Frequency
(MHz)
R2
(kX)
R3
(kX)
C3
(mF)
C4
(mF)
13 301
100
30
0 01 0 001
13 5
100
30
0 01 0 001
14 75
100
33
0 01 0 001
17 734
100
39
0 01 0 001
10 738
100
22
0 01 0 001
12 273
100
27
0 01 0 001
14 318
100
30
0 01 0 001
Xtal Loop Filter Components (Approximate)
Frequency
(MHz)
R2
(kX)
R3
(MX)
C3
(pF)
C4
(pF)
13 301
100
43
68
68
13 5
100
43
68
68
14 75
100
43
68
68
17 734
100
43
68
68
10 738
100
43
68
68
12 273
100
43
68
68
14 318
100
43
68
68
11
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