saa7803 NXP Semiconductors, saa7803 Datasheet - Page 53

• Manufacturer Part Number: saa7803
• Description: Saa7803 One Chip Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13695
Objective data sheet
6.7.5.2 Level initialization
6.7.5.3 Sledge control
6.7.5.4 Tracking control
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
time period:
The microprocessor can move the sledge in both directions via the steer sledge
command.
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 microprocessor, 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 use a track-count mechanism. In this mode, track
counting results in an ‘automatic return-to-zero track’ to avoid major disturbances in the
audio output and providing 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 microprocessor 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.
Fig 33. Bode diagram of radial PID system
•
•
•
300 ms. This start-up time period may coincide with the last part of the motor start-up
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 50 nm
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).
amplitude
rad_gain
(dB)
rad_int_strength
5
Rev. 01 — 19 April 2005
I
rad_int
1
P
rad_lead_length
2
D
rad_pole_lead
3
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
rad_pole_noise
One chip CD audio device
4
SAA7803
frequency
001aab776
(log Hz)
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