SAA7324H NXP Semiconductors, SAA7324H Datasheet - Page 30

• 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
During the actuator jump mode, velocity control with a
PI controller is used for the actuator. The sledge is then
continuously controlled using the filtered value of the radial
PID output. All filter parameters (for actuator and sledge)
are user programmable.
In the sledge jump mode maximum power (user
programmable) is applied to the sledge in the correct
direction while the actuator becomes idle (the contents of
the actuator integrator leaks to zero just after the sledge
jump mode is initiated). The actuator can be electronically
damped during sledge jump. The gain of the damping loop
is controlled via the hold_mult parameter.
The fast track jumping circuitry can be enabled/disabled
via the xtra_preset parameter.
7.14.4.5
The loop gain of the radial control loop can be corrected
automatically to eliminate tolerances in the radial 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).
This gain control differs from the level initialization. The
level initialization should be performed first.
The disadvantage of using the level initialization without
the gain control is that only tolerances from the front-end
are reduced.
7.14.5
The Track Position Signal (TPI) is a flag which is used to
indicate whether the radial spot is positioned on the track,
with a margin of
the Radial Polarity flag (RP) the relative spot position over
the tracks can be determined.
2000 Jun 26
handbook, full pagewidth
Digital servo processor and Compact Disc
decoder with integrated DAC (CD10 II)
sat1
sat2
O
FF
Radial automatic gain control loop
-
TRACK COUNTING
1
4
of the track-pitch. In combination with
DECIMATION
FILTER
Fig.21 Block diagram of defect detector.
FILTER
FAST
FILTER
SLOW
30
These signals are, however, afflicted with some
uncertainties caused by:
In order to determine the spot position with sufficient
accuracy, extra conditions are necessary to generate a
Track Loss signal (TL) and an off-track counter value.
These extra conditions influence the maximum speed and
this implies that, internally, one of the following three
counting states is selected:
1. Protected state: used in normal play situations. A good
2. Slow counting state: used in low velocity track jump
3. Fast counting state: used in high velocity track jump
7.14.6
A defect detection circuit is incorporated into the
SAA7324. If a defect is detected, the radial and focus error
signals may be zeroed, resulting in better playability.
The defect detector can be switched off, applied only to
focus control or applied to both focus and radial controls
under software control (part of foc_parm1).
The defect detector (see Fig.21) has programmable set
points selectable by the parameter defect_parm.
Disc defects such as scratches and fingerprints
The HF information on the disc, which is considered as
noise by the detector signals.
protection against false detection caused by disc
defects is important in this state.
situations. In this state a fast response is important
rather than the protection against disc defects (if the
phase relationship between TL and RP of
is affected too much, the direction cannot then be
determined accurately).
situations. Highest obtainable velocity is the most
important feature in this state.
D
GENERATION
EFECT DETECTION
DEFECT
PROGRAMMABLE
HOLD-OFF
Product specification
SAA7324
1
2
MBG421
radians
defect
output