Focus System
The focus error output of A, B, C and D are given to Pin 27. C4 is required for oscillation-
proof. R7 is set such that FEOUT of Pin 27 becomes 1.46 Vp-p.
During alignment procedure, the DSP IC (MN662790) will adjust the focus balance voltage
V
FBAL
from Pin 30. V
FBAL
varies with reference to the center voltage V
REF2
(=1.65 V) within
±0.5 V.
The focus gain will change according to the type of disc. For normal disc or CDR disc,
V
GCTRL
is set to V
REF2
; for CDRW disc V
GCTRL
is set to V
REF2
- 0.75 V. At the same time, the
tracking gain is changed too.
A B
C D
F
PDIC
E
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