HA12220 Hitachi Semiconductor, HA12220 Datasheet - Page 12

• Manufacturer Part Number: HA12220
• Description: CD-ROM Drive Head Amplifier IC
• Manufacturer: Hitachi Semiconductor

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.
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.
Rev.1, Apr. 1997, page 12 of 20
28
1
2
3
RF1
RF2
RF3
RF4
160k
160k
160k
160k
10p
Figure 9 Mirror Detection, Defect Detection
from AGC
Figure 10 Defect Detection Waveform
(a) Pin 22
(b) Pin 20
Figure 8 Focus Error Amplifiers
160k
160k
10p
–
+
FE
DEFECT
FVR2
MIRR
21
DFH
0.015
10p
160k
+
–
MIRH
MIRR
FA2
DFT
Offset
20
19
18
FVR
Gain=12dB Typ
0.033
HD49250
HD49250
+
–
FA
FE
9