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20
FESEL 0, 1
Offset Add.
circuit
FEG
1.65V
FE
3.3V
1.65V
FBAL
x1.17
x1
x1
x1
7
60
59
58
57
52
51
50
49
Detect
Amplitude
A/D
PWM
PLL
57
109
22
106
IC201
S-Curve : about 1.65Vpp
S-Center : 1.65V
F1
F2
E2
E1
A
B
C
D
D A
Tracking
B
C
3. SERVO SIGNAL
3-1. FOCUSING ERROR (FE)
Focusing Error circuit
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.