CXD3018Q/R
§5-10. DFCT Countermeasure Circuit
The DFCT countermeasure circuit maintains the directionality of the servo so that the servo does not become
easily dislocated due to scratches or defects on discs.
Specifically, this operation is achieved by detecting scratches and defects with the DFCT signal generation circuit,
and when DFCT goes high, applying the low-frequency component of the error signal before DFCT went high to
the FCS and TRK servo filter inputs. (See Fig. 5-13.)
In addition, these operations are activated by the default. They can be disabled by setting D7 (DFSW) of $38 to 1.
Hold filter
Input register
Error signal
Hold register EN
DFCT
Servo filter
Fig. 5-13
§5-11. Anti-shock Circuit
When vibrations occur in the CD player, this circuit forces the TRK filter to switch to gain-up mode so that the
servo does not become easily dislocated. This circuit is for systems which require vibration countermeasures.
Concretely, vibrations are detected using an internal anti-shock filter and comparator circuit, and the gain is
increased. (See Fig. 5-14.)
The comparator level is fixed to 1/16 of the maximum comparator input amplitude. However, the comparator
level is practically variable by adjusting the value of the anti-shock filter output coefficient K35.
This function can be turned on and off by D19 of $1 when the brake circuit (described hereafter) is off. (See
Table 5-17.)
This circuit can also support an external vibration detection circuit, and can set the TRK servo filter to gain-up
mode by inputting high level to the ATSK pin.
When the upper 4 bits of the command register are 1 (h), vibration detection can be monitored from the SENS
pin. It can also be monitored from the ATSK pin by setting $3F command ASOT to 1.
ATSK
SENS
Anti-shock
filter
Comparator
TE
TRK gain-up
filter
TRK
PWM Gen.
TRK gain normal
filter
Fig. 5-14
– 96 –
ETC [ ETC ]
