HA12220F Datasheet, PDF (10/20 Pages) Hitachi Semiconductor – CD-ROM Drive Head Amplifier IC

HA12220F
RF Amplifiers
The output from PDIC is summed by RFS amplifier.
Figure 4 shows the equivalent circuit for the EQ block in figure 3. The peaking characteristics can be
changed with 4-bit data from the HD49250.
On resistance of SC1 to SC4 are 600Ω Typ.
28 ^{RF1 12k}
1 ^{RF2 12k}
2 ^{RF3 12k}
3 ^{RF4 12k}
EQ
–
+
RFS
to AGC
Figure 3 RFS Amplifier
4p 8p 16p
SC3 SC2 SC1 SC4
0.3p
1.58k
4k 4k
Figure 4 RFS Amplifier Equalizer Equivalent Circuit
The RFS amplifier output is input to the AGC amplifier internally in the IC.
Pin 24 is used to connect the capacitor that sets cut-off frequency of high-pass filter between the RFS
amplifier and the AGC amplifier. The cut-off frequency will typically be 80Hz with the external constants
shown in figure 5.
The RF signal is rectified by an internal resistor and an external capacitor connected to pin 23.
The pins 28, 1, 2, and 3 expect an input level of about 0.1Vpp. The AGC amplifier output (pin 22) will
have an amplitude of 1.2Vpp Typ.
When CD-RW mode is set by 1-bit data from the HD49250, the AGC amplifier gain is increased by 12dB.
This allows the IC to output a 1.2Vpp Typ amplitude even during CD-RW playback.
to HD49250
1µ 0.1µ
24 23
22
RFC AGCF AGCO
AGC
Gain changing
to DEFECT MIRR
from RFS
Figure 5 AGC Amplifier
Rev.1, Apr. 1997, page 10 of 20