CXD2585Q Datasheet, PDF (93/127 Pages) Sony Corporation – CD Digital Signal Processor with Built-in Digital Servo

CXD2585Q
§ 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, these operations are 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.
Error signal
Input register
Hold Filter
DFCT
Hold register EN
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 (Hex), vibration detection can be monitored from the
SENS pin.
It also can be monitored from the ATSK pin by setting the ASOT command of $3F to 0.
ATSK
TE
Anti Shock
Filter
Comparator
TRK Gain Up
Filter
TRK Gain Normal
Filter
Fig. 5-14.
– 93 –
TRK
PWM Gen
SENS