saa7806 NXP Semiconductors, saa7806 Datasheet - Page 56

• Manufacturer Part Number: saa7806
• Description: Saa7806 One Chip Automotive Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13697
Objective data sheet
Fig 35. Laser control circuit
laser power
laser_clk32MHz
6.7.10 Driver interface
laser_clk8MHz
DAC
6.8 Laser interface
Vmon_dac
When the automatic sequencers are not used it is possible to generate timer interrupts,
defined by the time_parameter coefficient.
The control signals (pins RA, FO and SL) for the mechanism actuators are pulse density
modulated. The modulating frequency can be set to either 1.0584 MHz or 2.1168 MHz;
controlled via the xtra_preset parameter. An analog representation of the output signals
can be achieved by connecting a first-order low-pass filter to the outputs.
During reset (i.e. pin RESET_N is held LOW) the RA, FO, and SL pins are
high-impedance. At all other times, when the laser is switched off, the RA and FO pins
output a 2 MHz, 50 % duty cycle signal.
The laser diode pre-amp function is built onto the SAA7806 and is illustrated in
The current can be regulated, up to 120 mA, in four steps ranging from 58 % up to full
power. The voltage derived from the monitor diode is maintained at a steady state by the
laser drive circuitry, regulating the current through the laser diode.
laser_comp_out
TIMING AND CONTROL LOGIC
COUNTER
UP/DOWN
Rev. 01 — 20 June 2005
SIGMA
DELTA
DAC
laser_pdmin
laser_ion
One chip automotive CD audio device
LASER DIODE
MONITOR
AND
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
001aab779
SAA7806
76
77
78
LPOWER
LASER
MONITOR
Figure
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35.