cxd2548r Sony Electronics, cxd2548r Datasheet - Page 85

• Manufacturer Part Number: cxd2548r
• Description: Cd Digital Signal Processor With Built-in Digital Servo And Dac
• Manufacturer: Sony Electronics

§4-10. DFCT Countermeasure Circuit
The DFCT countermeasure circuit performs operations to maintain 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 performing scratch and defect detection 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. 4-8.)
In addition, these operations are activated by the default. They can be disabled by setting D7 (DFSW) of $38
to 1.
§4-11. Anti-Shock Circuit
When vibrations are produced in the CD player, this circuit forces the TRK filter to assume gain-up status 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. 4-9.)
The comparator level is fixed to 1/16 of the maximum comparator input amplitude. However, the comparator
level is practically variable by adjusting 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 4-5.)
This circuit can also support an external vibration detection circuit, and can set the TRK servo filter to gain-up
status by inputting high level to the ATSK pin.
When the serial data is $1, vibration detection can be monitored from the SENS pin.
TE
Error signal
TRK Gain Normal
TRK Gain Up
Input register
Anti Shock
Filter
Filter
Filter
Comparator
Fig. 4-8.
Fig. 4-9.
– 85 –
Servo Filter
Hold Filter
DFCT
ATSK
PWM Gen
TRK
EN
Hold register
CXD2548R
SENS