EL4584C Elantec Semiconductor, Inc. (acquired by Intersil), EL4584C Datasheet - Page 11

• Manufacturer Part Number: EL4584C
• Description: Horizontal Genlock, 4FSC
• Manufacturer: Elantec Semiconductor, Inc. (acquired by Intersil)

5 Now we can solve for C
C
C
R
6 Notice R
3
4
3
transfer function C
reverse bias control voltage and C
capacitance Since F(V
probably best to build the VCO and measure
K
surement are shown below The slope of the
curve is determined by linear regression tech-
niques and equals K
K
sign R
be adjusted to compensate for any static phase
error T at lock but if made too large will
slow loop response If R
(see timing diagrams) increases and if R
creases T decreases For LDET to be low at
lock
ate high frequency noise from the charge
pump
e
e
e
VCO
VCO
We choose R
K
C
10
K
2N
N
3
d
l
d
T
K
about 2 5V The results of one such mea-
F
K
e
e
2
OSC
VCO
VCO
l
should be large around 100k and can
2 n
2
0 001 F
6 05 Mrad S V
k
n
has little effect on the loop filter de-
vs V
50 ns C
e
e
C
3
(4 77e
(4 77e
LC VCO
e
(2)(910)(1)(5000)
(910)(5000)
v
30 k
4
e
is used mainly to attenu-
VCO
b
b
F(V
C
3
2
5)(6 05e6)
5)(6 05e6)
) is nonlinear it is
for convenience
C
is made smaller T
C
4
) where V
For our example
and R
2
V
e
e
is varactor
3
0 01 F
31 5 k
C
is the
4584 – 14
2
in-
11
Lock Time
Let
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 (
decreased damping also decreases loop stability
it is sometimes desirable to design slightly over-
damped (
stability
Frequency
Frequency
Xtal Loop Filter Components (Approximate)
LC Loop Filter Components (Approximate)
(MHz)
(MHz)
13 301
13 5
14 75
17 734
10 738
12 273
14 318
13 301
13 5
14 75
17 734
10 738
12 273
14 318
e
e
Horizontal Genlock 4 F
R
1) occurs at minimum lock time Because
3
C
l
3
1) trading lock time for increased
As T increases damping increases
Typical Loop Filter
(k )
(k )
100
100
100
100
100
100
100
100
100
100
100
100
100
100
R2
R2
EL4584C
(M )
(k )
R3
R3
30
30
33
39
22
27
30
4 3
4 3
4 3
4 3
4 3
4 3
4 3
( F)
0 01
0 01
0 01
0 01
0 01
0 01
0 01
(pF)
C3
C3
68
68
68
68
68
68
68
0 001
0 001
0 001
0 001
0 001
0 001
0 001
( F)
(pF)
4584 – 16
C4
SC
C4
6 8
6 8
6 8
6 8
6 8
6 8
6 8