SAF7849HL/M295,557 NXP Semiconductors, SAF7849HL/M295,557 Datasheet - Page 58

• 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
6.6.6.4 Access
6.6.6.5 Radial automatic gain control loop
6.6.7 Off-track counting
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.
The access procedure is divided into two different modes depending on the requested
jump size; see
Table 14.
[1]
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 remaining, 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.
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 charge current reduces 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 or disabled via parameter xtra_preset.
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.
The Track Position Indicator (TPI) signal is a flag which is used to indicate whether the
radial spot is positioned on the track, with a margin of
combination with the Radial Polarity (RP) flag the relative spot position over the tracks can
be determined.
Access type
Actuator jump
Sledge jump
Microcontroller presettable.
Radial servo access procedure modes
Table
14.
One chip CD audio device with integrated MP3/WMA decoder
Rev. 02 — 9 May 2008
Jump size
brake_distance
brake_distance - 32768
[1]
1
4
of the track-pitch. In
Access speed
decreasing velocity
maximum power to sledge
SAF784x
© NXP B.V. 2008. All rights reserved.
58 of 93
[1]