TDA1301 Philips Semiconductors, TDA1301 Datasheet - Page 6

• Manufacturer Part Number: TDA1301
• Description: Digital servo processor DSIC2
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Automatic gain adjustment: as a result of this initialization
the amplitude of the RE signal is adjusted 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 50 nm.
TPI level generation: the accuracy of the initialization
procedure is such that the duty cycle range of TPI
becomes 0.4 < < 0.6 { = TPI(HIGH)/TPI(period)}.
S
Sledge moves to reference position (end_stop_switch) at
the inner side of the disc with user defined voltage.
T
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
Upon request from the microcontroller S-curve extension
over 2 tracks is used, automatically changing to access
control when these two tracks are exceeded.
Both modes of S-curve extension make use of a
track-count mechanism as described in Section “Off-track
counting” . In this mode track counting results in automatic
‘return-to-zero track’, to avoid major music rhythm
disturbances in the audio output to provide improved
shock resistance. The sledge is continuously controlled
using the filtered value of the integrator contents of the
actuator, or upon request by the microcontroller. The
microcontroller can read out this integrator value and
provides the sledge with step pulses to reduce power
consumption. Filter coefficients of the continuous sledge
control can be preset by the user.
A
The access procedure is divided into 2 different modes,
depending on the requested jump size.
The access procedure makes use of a track counting
mechanism (see Section “Off-track counting” ), a velocity
signal based upon the number of tracks passed within a
fixed time interval, a velocity setpoint calculated from the
number of tracks to go and a user programmable
parameter indicating the maximum sledge performance.
If the number of tracks to go is greater than break_dist the
sledge jump mode will be activated (otherwise the actuator
jump will be performed). The requested jump size together
with the required sledge braking distance at maximum
access speed defines the value break_dist.
During the actuator jump mode, velocity control with a PI
controller is used for the actuator.
March 1994
RACKING CONTROL
LEDGE HOME
CCESS
Digital servo processor (DSIC2)
3
4
track.
7
The sledge is then continuously controlled using the
filtered value of the integrator contents of the actuator.
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).
Table 1 Access procedure.
Note
1. Can be preset by the microcontroller.
Defect detector
A built-in defect detector prevents the light spot from going
out-of-focus and going off-track due to disc drop-out
excitations. The defect detector can be switched ON or
OFF under software control and can be applied to the
focus control only, or to both the focus and radial control.
The detected defect signal holds the focus and radial loop
filter outputs. The hold signal is generated whenever the
reflected light intensity drops rapidly (<1.5 ms) down to
75% of the actual intensity level.
Shock detector
The shock detector can be switched ON during normal
track following. The shock detector detects, within an
adjustable frequency band, whether the disturbances in
the radial spot position relative to the track exceeds an
adjustable level. Every time the radial tracking error (RE)
exceeds this level the radial control bandwidth is switched
directly to twice the original bandwidth.
The shock detection level is adjustable in 64 steps from
0 to 100% of the nominal radial amplitude. The bandpass
filter (BPF) lower frequency ( 3 dB) can be fixed at 0 or
20 Hz. Independently, the BPF upper frequency ( 3 dB)
can be fixed at 750 or 1850 Hz.
Off-track counting
TPI is a flag which is used to indicate whether the spot is
positioned on the track (with a margin of
track-pitch).
Actuator
jump
Sledge
jump
ACCESS
TYPE
1
break
break distance
JUMP SIZE
(1)
32768
(1)
decreasing velocity
minimum power to
sledge
Product specification
ACCESS SPEED
TDA1301T
1
4
(1)
of the