SAF7849HL/M295,557 NXP Semiconductors, SAF7849HL/M295,557 Datasheet - Page 57

• Manufacturer Part Number: SAF7849HL/M295,557
• Description: IC AUD DECODER 144LQFP
• Manufacturer: NXP Semiconductors
• Type: Audio Decoderr

Specifications of SAF7849HL/M295,557

• Applications: Audio CD
• Voltage - Supply, Analog: 3 V ~ 3.6 V
• Voltage - Supply, Digital: 1.8V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 144-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 935287932557

NXP Semiconductors
SAF784X_2
Product data sheet
6.6.5.4 Focus loss detection and fast restart
6.6.5.5 Focus loop gain switching
6.6.5.6 Focus automatic gain control loop
6.6.6.1 Level initialization
6.6.6.2 Sledge control
6.6.6.3 Tracking control
6.6.6 Radial servo system
Whenever focus is lost 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 ms to 300 ms depending on the programmed coefficients of the
microcontroller.
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.
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).
During startup, 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 microcontroller 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 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 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 microcontroller can read the average
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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
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)
One chip CD audio device with integrated MP3/WMA decoder
Rev. 02 — 9 May 2008
10 % around the nominal RE amplitude
50 nm
SAF784x
© NXP B.V. 2008. All rights reserved.
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