PRELIMINARY DRAFT
Functional Decriptions
The channel is controlled by a state machine that automatically starts timing recovery and
deals with defects. This ensures quick recovery from defects and fast data acquisition
after seeks.
The CL-CR3710 contains a versatile digital block that can be used to monitor the ongoing
‘health’ or ‘quality’ of the channel, and that enables accurate equalization calibration to
compensate for wide variations in disc resolution.
Servo Channel
The CL-CR3710 contains an integrated servo system that can control either a CDROM or
a DVD mechanism, with the following features:
• Servo Control Processor (SCP), implementing algorithms designed specifically
for optical disc drives
• Supports dual pick up for CD and DVD applications
• Integrated RF amplifier with Laser Diode Automatic Power Control (LD APC)
• Track counter with velocity estimation
• Multi-function register banks
• External microcontroller interface circuitry
• Programmable Sample Rate Subsystem
Figure 2 shows the CL-CR3710 in a complete servo system. Four control loops can be
processed by this chip: focus, track, sled, spindle. Since the CL-CR3710 contains a
processor, control algorithms and interface circuitry, little external hardware and little
microcontroller intervention is required to implement the servo system.
Pickup/Sensor Interface
The Pickup Interface is the input to the servo control processor (SCP). This circuitry
provides the analog and digital processing needed before the SCP can process the
control signals from the sensors. Since laser diode automatic power control and reference
voltage generation are also provided, the CL-CR3710 can be connected directly to the
pick up electronics without the need for an external RF amplifier.
Servo Control Processor
The SCP does all the processing necessary to control all four servo loops with little
loading of the external microcontroller. The microcontroller sends setup information and
commands to the control system through the microcontroller interface. It can also monitor
key metrics and change control variables to optimize system performance.
All parameter variables and SCP instructions are stored in internal RAM. Since the CL-
CR3710 is a RAM based device, the microcontroller must first initialize these RAMs
before servo operations can begin.
Servo DACs
Control outputs for the sled, focus, and track loops are converted to analog through an
array of three 11-bit DACs. The spindle loop has a pulse width modulated (PWM) output.
DS587PP1 - rev 0.1 April 11, 2002
Copyright 2002 Cirrus Logic Inc.
CONFIDENTIAL
6
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