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3. SERVO SIGNAL
3-1. FOCUSING ERROR (FE)
F1
36
F2
37
E2
39
E1
40
A
43
B
47
C
46
D
44
D A
C
B
FE for DVD-ROM,CD are made from 4D(A,B,C,D).
FE S-curve amplitude is detected from IC201 109 pin and FE gain is controlled by register "FEG" to keep 1.65V
amplitude.
Center Voltage of FE is about 1.65V.
Offset adjustment for added FE keep max voltage with jitter min.
Added offset quantity is programmable by current which feed into IC101 7 pin from IC201 57 pin.
FE for DVD-RAM 2.6G,4.7G is obtained from 4D(A,B,C,D) or sub spot(Sub beam) (E1,E2,F1,F2).
For DVD-RAM 2.6G, 4.7G, offset is occurred when track is crossed.
The reason for sub spot(sub beam) add is cancel of offset.
20
x1.17
x1
FESEL 0, 1
x1
x1
Tracking
Focusing Error circuit
FEG
Offset Add.
circuit
1.65V
FBAL
7
S-Curve : about 1.65Vpp
S-Center : 1.65V
A/D
18
109
FE
3.3V
PWM
57
IC201
Detect
Amplitude
PLL
106
1.65V
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