saa7327 NXP Semiconductors, saa7327 Datasheet - Page 27

• Manufacturer Part Number: saa7327
• Description: Digital Servo Processor And Compact Disc Decoder With Integrated Dac For Video Cd Cd7 Ii
• Manufacturer: NXP Semiconductors

Philips Semiconductors
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.20.
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:
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 dropout detection.
2000 Jun 26
FE
FE
SHADEN BIT
Digital servo processor and Compact Disc
decoder with integrated DAC for video CD (CD7 II)
n
n
=
=
-------------------- -
D1
2
1
D1 D2
S
IGNAL CONDITIONING
+
–
-------------------- -
D1
D1 D2
D2
+
–
–
D2
-------------------- -
D3
D3 D4
REGISTER
R1 and R2
n
magnitude
SHADOW
control for
, is further processed by a
C signal
–
+
diodes
D4
ADDRESS
1100
DATA
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
27
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:
RE
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 SAA7327 during initialization.
s
= (R1
(0.042).I
(0.083).I
(0.125).I
(0.167).I
(0.208).I
(0.25).I
(0.292).I
(0.333).I
(0.375).I
(0.417).I
(0.458).I
(0.5).I
(0.542).I
(0.583).I
(0.625).I
(0.667).I
R2)
ref
ref
ref
ref
ref
ref
ref
ref
ref
ref
ref
ref
= 12.075 A (nominal)
ref
ref
ref
ref
= 6.034 A (nominal)
= 1.006 A (nominal)
= 2.013 A (nominal)
= 3.019 A (nominal)
= 4.025 A (nominal)
= 5.031 A (nominal)
= 7.044 A (nominal)
= 8.05 A (nominal)
= 9.056 A (nominal)
= 10.063 A (nominal)
= 11.069 A (nominal)
= 13.081 A (nominal)
= 14.088 A (nominal)
= 15.094 A (nominal)
= 16.1 A (nominal)
re_gain + (R1 + R2)
FUNCTION
(R1 + R2)
Product specification
SAA7327
re_offset
sum_gain]
INITIAL
reset