CXD3003R datasheet(105/137 Pages) SONY

105 / 137 page

– 105 –

CXD3003R

§5-12. Brake Circuit

Immediately after a long distance track jump it tends to be hard for the actuator to settle and for the servo to

turn on.

The brake circuit prevents these phenomenon.

The brake circuit is to use tracking drive as a brake by cutting unnecessary portions of it utilizing the 180°

offset in the RF envelope and tracking error phase relationship which occurs when the actuator traverses the

track in the radial direction from the inner track to the outer track and vice versa. (See Figs. 5-15 and 5-16.)

Concretely, this operation is achieved by masking the tracking drive using the TRKCNCL signal generated by

loading the MIRR signal at the edge of the TZC (Tracking Zero Cross) signal.

The brake circuit can be turned on and off by D18 of $1. (See Fig. 5-17.)

TRK

DRV

FWD

JMP

REV

JMP

Servo ON

Trace

MIRR

TZC

Edge

TRKCNCL

TRK

DRV

SENS

TZC out

Inner track

Outer track

TRK

DRV

REV

JMP

FWD

JMP

Servo ON

Trace

MIRR

TZC

Edge

TRKCNCL

TRK

DRV

SENS

TZC out

Outer track

Inner track

Fig. 5-15.

Fig. 5-16.

D23 to D20

D19 to D16

1 0

∗ ∗

∗ ∗ ∗

∗ 1 ∗ ∗

∗ 0 ∗ ∗

∗ ∗ 0 ∗

∗ ∗ 1 ∗

∗ ∗ ∗ 1

∗ ∗ ∗ 0

ANTI SHOCK ON

ANTI SHOCK OFF

BRAKE ON

BRAKE OFF

TRACKING GAIN NORMAL

TRACKING GAIN UP

TRACKING GAIN UP FILTER SELECT 1

TRACKING GAIN UP FILTER SELECT 2

0 0 0 1

TRACKING

CONTROL

Fig. 5-17.

∗: Don’t care

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