CXD3003 datasheet(104/137 Pages) SONY

104 / 137 page

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CXD3003R

§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 scratch and defect with the DFCT signal generation

circuit, and when DFCT goes high, applying the low frequency element 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.

Input register

Hold register

Hold Filter

Servo Filter

Error signal

DFCT

Fig. 5-13.

§5-11. Anti-Shock Circuit

When vibrations occurs 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 8 bits of the command register are $1, vibration detection can be monitored from the SENS

pin.

Anti Shock

Filter

TRK Gain Up

Filter

TRK Gain Normal

Filter

TRK

PWM Gen

ATSK

SENS

Comparator

Fig. 5-14.

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