saa7327 NXP Semiconductors, saa7327 Datasheet - Page 26

• 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
7.14.1
The photo detector in conventional two-stage three-beam
Compact Disc systems normally contains six discrete
diodes. Four of these diodes (three for single foucault
systems) carry the Central Aperture signal (CA) while the
other two diodes (satellite diodes) carry the radial tracking
information. The CA signal is processed into an HF signal
(for the decoder function) and LF signal (information for
the focus servo loop) before it is supplied to the SAA7327.
The analog signals from the central and satellite diodes
are converted into a digital representation using
Analog-to-Digital Converters (ADCs).
Table 12 Shadow register settings to control diode input current ranges
2000 Jun 26
SHADEN BIT
Digital servo processor and Compact Disc
decoder with integrated DAC for video CD (CD7 II)
Servo part
1
D
IODE SIGNAL PROCESSING
REGISTER
magnitude
SHADOW
control for
D1 to D4
A signal
diodes
ADDRESS
1010
DATA
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
26
The ADCs are designed to convert unipolar currents into a
digital code. The dynamic range of the input currents is
adjustable within a given range, which is dependent on the
value of the external reference current (I
the values programmed in shadow registers A and C.
The magnitude of the signal currents for the central
aperture diodes D1 to D4 and the radial diodes R1 and R2
are programmed separately to sixteen separate current
ranges.
The maximum input currents with an external 30 k
reference current resistor are given in Table 12.
(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
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)
FUNCTION
Product specification
ref
SAA7327
) resistor and
INITIAL
reset