SAA7374GP PHILIPS [NXP Semiconductors], SAA7374GP Datasheet - Page 25

• Manufacturer Part Number: SAA7374GP
• Description: Low voltage digital servo processor and Compact Disc decoder CD7LV
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
Where f
V
can be selected under software control via the preset latch
command. With this command the V
to 2.5 V then modified, decremented one level or
incremented, by resenting the command the required
number of times. In the application V
V
7.14.2
The digital codes retrieved from the ADCs are applied to
logic circuitry to obtain the various control signals. The
signals from the central aperture diodes are processed to
obtain a normalised focus error signal.
where the detector set-up is assumed as shown in Fig.19.
In the event of single Foucault focusing method, the signal
conditioning can be switched under software control such
that the signal processing is as follows;
1998 Feb 26
I
I
FE
FE
handbook, full pagewidth
in max central
in max satellite
RH
SSA1
Low voltage digital servo processor and
Compact Disc decoder (CD7LV)
n
n
is generated internally, and there are 32 levels which
=
=
.
sys
2
D1 D2
--------------------- -
D1
S
IGNAL CONDITIONING
= 4.2336 MHz.
–
+
D1 D2
--------------------- -
D1
D2
+
–
=
=
D2
–
single Foucault
f
--------------------- -
D3
sys
D3 D4
f
SATELLITE
SATELLITE
DIODE R1
DIODE R2
sys
D3
+
–
D4
V
D1
D2
V
RH
RH
–
–
V
V
RL
RL
RH
RL
voltage can be set
1.0 10
is connected to
0.5 10
Fig.19 Detector arrangement.
–
6
–
6
A
A
astigmatic focus
SATELLITE
SATELLITE
DIODE R1
DIODE R2
D2
D4
25
RE
The error signal, FE
proportional integral and differential (PID) filter section.
A Focus OK (FOK) flag is generated by means of the
central aperture signal and an adjustable reference level.
This signal is used to provide extra protection for the
track-loss (TL) generation, the focus start-up procedure
and the drop out detection.
The radial or tracking error signal is generated by the
satellite detector signals R1 and R2. The radial error signal
can be formulated as follows;
where the index ‘s’ indicates the automatic scaling
operation which is performed on the radial error signal.
This scaling is necessary to avoid non-optimum dynamic
range usage in the digital representation and reduces the
radial bandwidth spread. Furthermore, the radial error
signal will be made free from offset during start up of the
disc.
The four signals from the central aperture detectors,
together with the satellite detector signals generate a track
position signal (TPI) which can be formulated as follows;
TPI = sign [(D1 + D2 + D3 + D4)
Where the weighting factor sum_gain is generated
internally by the SAA7374 during initialization.
D1
D3
s
=
R1 R2
–
n
re_gain
, is further processed by a
+
double Foucault
SATELLITE
SATELLITE
DIODE R1
DIODE R2
R1 R2
D1
D2
D3
D4
(R1 + R2)
–
Product specification
MBG422
SAA7374
re_offset
sum_gain]