HA12220 データシートの表示（PDF） - Hitachi -> Renesas Electronics

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HA12220

CD-ROM Drive Head Amplifier IC

Hitachi -> Renesas Electronics 

HA12220F

FOK Detection Circuit

This detector is a comparator that generates the FOK signal. FOK is one of the signals that activate the

focus servo.

The FSA amplifier (fc = 53kHz Typ) summes the output from the PDIC. When this output signal becomes

lower than the reference voltage by Vth, pin 17 goes high. This Vth can be set by 2-bit data from the

HD49250.

Vth is set to 0.8V (0dB) after a reset.

Using µ-com ADC & DAC the voltage of pin 11 had better be set the same voltage as the voltage of pin 10

before focus searching in order to reduce the effect of DC offset voltage at FSA amplifier output.

28 RF1

1 RF2

2 RF3

3 RF4

120k

120k

120k

120k

5p

600k

–

+

FSA

BUF

–

+ 11

CO

FOK

+

–

FOK 17

CI 10

µ-COM DAC

µ-COM ADC

Figure 6 FOK Detection

APC

This circuit is for the Psub laser diode. This circuit is turned on or off by 1-bit data from the HD49250.

MD

6

APC

1k

LD

7

Figure 7 APC

Rev.1, Apr. 1997, page 11 of 20

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