SAA7324H NXP Semiconductors, SAA7324H Datasheet - Page 29

• Manufacturer Part Number: SAA7324H
• Manufacturer: NXP Semiconductors

Specifications of SAA7324H

• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 64
• Lead Free Status / Rohs Status: Compliant

Philips Semiconductors
7.14.3.4
Whenever FOK is false for longer than approximately
3 ms, it is assumed that the focus point is lost. A fast
restart procedure is initiated which is capable of restarting
the focus loop within 200 to 300 ms depending on the
programmed coefficients of the microcontroller.
7.14.3.5
The gain of the focus control loop (foc_gain) can be
multiplied by a factor of 2 or divided by a factor of 2 during
normal operation. The integrator value of the PID is
corrected accordingly. The differentiating (foc_pole_lead)
action of the PID can be switched at the same time as the
gain switching is performed.
7.14.3.6
The loop gain of the focus control loop can be corrected
automatically to eliminate tolerances in the focus loop.
This gain control injects a signal into the loop which is used
to correct the loop gain. Since this decreases the optimum
performance, the gain control should only be activated for
a short time (for example, when starting a new disc).
7.14.4
7.14.4.1
During start-up an automatic adjustment procedure is
activated to set the values of the radial error gain (re_gain),
offset (re_offset) and satellite sum gain (sum_gain) for TPI
level generation. The initialization procedure runs in a
radial open loop situation and is 300 ms. This start-up
time period may coincide with the last part of the motor
start-up time period:
7.14.4.2
The microcontroller can move the sledge in both directions
via the steer sledge command.
2000 Jun 26
Automatic gain adjustment: as a result of this
initialization the amplitude of the RE signal is adjusted to
within 10% around the nominal RE amplitude
Offset adjustment: the additional offset in RE due to the
limited accuracy of the start-up procedure is less than
TPI level generation: the accuracy of the initialization
procedure is such that the duty factor range of TPI
becomes 0.4 < duty factor < 0.6 (default duty
factor = TPI HIGH/TPI period).
Digital servo processor and Compact Disc
decoder with integrated DAC (CD10 II)
50 nm
R
ADIAL SERVO SYSTEM
Focus loss detection and fast restart
Focus loop gain switching
Focus automatic gain control loop
Level initialization
Sledge control
29
7.14.4.3
The actuator is controlled using a PID loop filter with user
defined coefficients and gain. For stable operation
between the tracks, the S-curve is extended over 0.75 of
the track. On request from the microcontroller, S-curve
extension over 2.25 tracks is used, automatically changing
to access control when exceeding those 2.25 tracks.
Both modes of S-curve extension make use of a
track-count mechanism. In this mode, track counting
results in an ‘automatic return-to-zero track’, to avoid
major music rhythm disturbances in the audio output for
improved shock resistance. The sledge is continuously
controlled, or provided with step pulses to reduce power
consumption using the filtered value of the radial PID
output. Alternatively, the microcontroller can read the
average voltage on the radial actuator and provide the
sledge with step pulses to reduce power consumption.
Filter coefficients of the continuous sledge control can be
preset by the user.
7.14.4.4
The access procedure is divided into two different modes
(see Table 13), depending on the requested jump size.
Table 13 Access modes
Note
1. Microcontroller presettable.
The access procedure makes use of a track counting
mechanism, a velocity signal based on a fixed number of
tracks passed within a fixed time interval, a velocity set
point calculated from the number of tracks to go and a user
programmable parameter indicating the maximum sledge
performance.
If the number of tracks remaining is greater than the
brake_distance then the sledge jump mode should be
activated or, the actuator jump should be performed.
The requested jump size together with the required sledge
breaking distance at maximum access speed defines the
brake_distance value.
Actuator jump 1 - brake_distance
Sledge jump
ACCESS
TYPE
Tracking control
Access
brake_distance - 32768 maximum
JUMP SIZE
(1)
Product specification
SAA7324
decreasing
velocity
power to
sledge
ACCESS
SPEED
(1)