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Philips SACD 1000/001 Service Manual Page 64

Dvd-video player.
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GB 108
SACD 1000
DVDALAS2plus Advanced Analogue
DVD Signal Processor and Laser Supply
• Operates with DVD-ROM,DVD-RAM, DVD+RW,
DVD-RW, CD-ROM and CD-RW media
• Operates up to 64x CD-ROM and 8x DVD-ROM
• Support for Dual Light pen DVD systems (DVD/CDRW)
• DVD-RAM (C) playback capability
• DVD-RAM Land-Groove servo polarity switching
• 3 different tracking servo strategies:
Conventional 3 beam tracking for CD
Differential Phase Detection (DPD) for DVD-ROM
(including option to emulate traditional drop out
detection; drop out concealment)
Advanced Push Pull with dynamic offset compensation
for DVD-RAM (recorded and unrecorded areas)
• Radial error signal for fast track counting (FTC)
• 2 different strategies to read header data:
- Full bandwidth Push Pull signal
- Left and Right side signal
• Universal photo diode IC interface using internal
conversion resistors and offset cancelation
• Flexible adaption to different light pen configurations
• Input buffer amplifiers with low-pass filtering
• RF data amplifier with wide (programmable) bandwidth
equivalent to 64xCD / 8x DVD when using equaliser
• Built-in equalisers cover CAV inner-outer disc range at
highest speed.
• Programmable RF gain for DVD-ROM / DVD-RAM /
CD-RW / CDROM applications(approx 50dB range)
• Balanced RF-Data signal transfer (single ended still
• Fully automatic laser control including stabilization and
an ON/OFF switch, plus a separate supplypin for power
• Automatic monitor diode polarity selection.
• 3 and 5 V compatible digital interface
• Enhanced signal conditioning in DPD circuit for optimal
tracking performance under noisy conditions.
Circuit-, IC descriptions and list of abbreviations
Plastic low pro?le QFP64; body 10 x 10 x 1.4 mm
The DVDALAS2 is an analogue preprocessor and laser
supply circuit for DVD / CD read only players. The device
contains data amplifiers, several options for radial tracking
and focus control. The preamplifier forms a versatile,
programmable interface between dual, voltage output
CD/DVD mechanisms to Philips' digital signal processor
family for CD and DVD (Gecko, HDR65, Iguano, etc..)
The device contains serval options for radial tracking:
Conventional 3 beam tracking for CD;
Differential Phase Detector (DPD) for DVD;
Push Pull for DVD-RAM with flexible L/R weighing to
compensate dynamic offsets e.g. beamlanding offset.
A radial error signal is generated to allow fast track count
(FTC) during track jumps.
The dynamic range of this preamp/processor combination
can be optimized for the LF servo and RF data paths. The
gain in both channels can be programmed separately. This
will guarantee an optimal playability for all kind of discs.
Several functions are included to allow playback of
DVD-RAM(C) discs:
• The header information can be read via the data output
path (RF)
• DC offset compensation techniques provide a fast
settling after disc errors.
• Radial servo Polarity switch for land/groove
• two settings for focus offset correction for land and
The device can accommodate astigmatic, single foucault
and double foucault detectors and can be used with P-type
lasers with N- or P-sub monitor diodes. After an initial
adjustment, the circuit will maintain control over the laser
diode current. With an on-chip reference voltage
generator, a constant and stabilized output power is
ensured independent of ageing. A separate power supply
connection allows the internal power dissipation to be
reduced by connecting a low voltage supply.


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