AN8808SB Datasheet, PDF (8/10 Pages) Panasonic Semiconductor – Three-Beam Method Head Amplifier IC for CD supporting the hologram pick-up

AN8808SB
ICs for CD/CD-ROM Player
Pins31 and 32 are used to make the resistance converting the current to voltage variable. When these pins are directly
connected to VREF and 20kΩ of resistance is connected between TE and TE–, and between TE and TEOUT respectively,
equivalent resistance to TEOUT is 629kΩ.
Table 2
VC
E/F
F/E
1.5V
0.14
7.0
2.5V
1.0
1.0
3.5V
7.0
0.14
The VCBA is for tracking balance adjustment in the same way of for focus. Table 2 shows the tracking balance ratio under the
same conditions as shown in Table 1.
• AGC
In order to absorb the attenuation of RF signal by disk, pick-up dispersion, finger print and other factors, AGC circuit for RF is
incorporated.
The input impedance of Pin8 is approx. 27.9kΩ. ByPin10 (ARF), the gain-controlled RF-signal is outputted. Input allowable
level is approx. 1VP–P ~ 500mVP–P ~ 250mVP–P, and output is 1VP–P. Pin9 is a connecting pin with capacity for constructing the
AGC loop filter, and it is recommended that the external capacitor of 1µF around should be connected to it for VCC.
RF
VCC
1µF
ARF
8
9
10
AGC
Figure 4 : AGC
• RFDET
The RFDET detects amplitude of RF signal inputted to Pin8. Threshold value is approx. 100mV (f= 500kHz), and RF Present
= L, RF Absent = H are outputted.
• BDO Detection
BDO is detected by the low speed detection circuit and high speed detection circuit. The high speed detection circuit is
incorporated. On the other hand, the capacitor of the low speed detection circuit must be connected to Pin13. The capacity value
is 2200pF and it is recommended that it should be connected for VCC. When this capacity value of Pin13 is increased, BDO is
detected with large RF missing rate. When it is decreased, BDO can be detected with small RF missing rate.
BDO present = H
BDO absent = L