Note: CLV servo control commands can set the TOFF pin low only in CLV mode. That pin will be at the high level

at all other times. Control of the TOFF pin by microprocessor command is only valid in CLV mode.

• CLV mode

In CLV mode the LC78620E detects the disk speed from the HF signal and provides proper linear speed using

several different control schemes by switching the DSP internal modes. The PWM reference period corresponds to

a frequency of 7.35 kHz. The V/P pin outputs a high level during rough servo and a low level during phase control.

• Rough servo gain switching

For 8 cm disks, the rough servo mode CLV control gain can be set about 8.5 dB lower than the gain used for 12 cm

disks.

• Phase control gain switching

The phase control gain can be changed by changing the divisor used by the dividers in the stage immediately

preceding the phase comparator.

No. 5130-13/34

LC78620E

Internal mode

V/P

Rough servo (velocity too low)

High

Low

High

Rough servo (velocity too high)

Low

High

High

Phase control (PCK locked)

PWM

PWM

Low

MSB

LSB

Command

RES = low

1 0 1 1 0 0 0 1

CLV PHASE COMPARATOR DIVISOR: 1/2

1 0 1 1 0 0 1 0

CLV PHASE COMPARATOR DIVISOR: 1/4

1 0 1 1 0 0 1 1

CLV PHASE COMPARATOR DIVISOR: 1/8

1 0 1 1 0 0 0 0

NO CLV PHASE COMPARATOR DIVISOR USED

q

q

MSB

LSB

Command

RES = low

1 0 1 0 1 0 0 0

DISC 8 SET

1 0 1 0 1 0 0 1

DISC 12 SET

q

q