HA12220F Datasheet, PDF (12/20 Pages) Hitachi Semiconductor – CD-ROM Drive Head Amplifier IC

HA12220F
Focus Error Amplifiers
The FE amplifier adds and subtracts the output from the PDIC.
FVR2 is a variable resistor used to increase the gain by 12dB in CD-RW mode. This variable resistor is set
by 1-bit data from the HD49250.
FVR is a variable resistor that changes the focus error gain over the range –8 to +8dB in ±4dB steps. This
variable resistor is set by 3-bit data from the HD49250.
An offset of between –0.7 and 0.7V (in 0.1V steps) is inserted into the focus error signal. This is set by 4-
bit data from the HD49250. The FE output cut-off frequency (fc) is 60kHz Typ.
28 ^{RF1 160k}
1 ^{RF2 160k}
2 ^RF3
3 ^{RF4 160k}
160k
10p
10p
160k
–
+
FE
160k
+FA2
–
Gain=12dB Typ
+FA
FVR2
–
160k
FVR
9
10p
FE
Offset
Figure 8 Focus Error Amplifiers
Defect Detection Circuit
When a scratched disc is played, the EFM RF signal has the shape shown in figure 10 (a). The defect
detection circuit detects the drop-out area of this signal.
from AGC
0.015µ
21
DFH
DEFECT
MIRR
DFT ₂₀
HD49250
MIRH ₁₉
0.033µ
MIRR ₁₈
HD49250
Figure 9 Mirror Detection, Defect Detection
(a) Pin 22
(b) Pin 20
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Figure 10 Defect Detection Waveform
Rev.1, Apr. 1997, page 12 of 20