Philips VAD8041 Service Manual page 34

EN 34 9. VAD8041
• Paedic
programmable gain pre-amplifier
• Eeprom
representing adjustments belonging to the OPU.
The laser control and diode signal processor ICs together with
an EEPROM are mounted on the OPU flex.
The laser control IC generates the DVD laser read and writing
signals needed for reading DVD discs and writing DVD+RW /
+R discs (write strategies of DVD+RW / +R discs).
The diode signal processor is an analogue pre-processor
adapted for the CD and CD-R / RW read function.
The EEPROM contains information about writing current,
writing strategies and other parameters belonging to the OPU.
9.7 Motor and Servo drivers
The SA56202 is a one-chip motor driver IC that is capable to
drive all motors of CD or DVD systems: spindle, sled and
loading motors. The driver for the 3-phase, brushless, hall-
commutated spindle motor uses True-Silent PWMTM. This
proprietary technology ensures that all 3-phase motor currents
are sinusoidal resulting in an optimally silent and power-
efficient driver. Internal compensation of the spindle motor's
back-EMF enables the driver to operate in current-steering
mode without using external power-dissipating sense resistors.
The driver for the 2-phase sled stepper motor operates in
current-steering PWM mode. In addition the IC contains four
full-bridge linear channels that are used to drive the loading
motor.
The 3D actuators (focus, tracking and tilt) are driven by IC
7409, BA5995FM.
Circuit Descriptions, Abbreviation List, and Data Sheets
integrated photo detector with
containing a number of values