SAA7373 Datasheet, PDF (23/60 Pages) NXP Semiconductors – Digital servo processor and Compact Disc decoder CD7

Philips Semiconductors
Digital servo processor and Compact Disc
decoder (CD7)
Product specification
SAA7373
7.13.1.4 CDV/CAV output mode
In the CDV motor mode, the FIFO position will be put in
pulse-width modulated form on the MOTO1 pin [carrier
frequency (300 × d) Hz], where ‘d’ is the disc speed factor.
The PLL frequency signal will be put in pulse-density
modulated form (carrier frequency 4.23 × n MHz) on the
MOTO2 pin. The integrated motor servo is disabled in this
mode.
The PWM signal on MOTO1 corresponds to a total
memory space of 20 frames, therefore the nominal FIFO
position (half full) will result in a PWM output of 60%.
In the lock to-disc (CAV) mode the CDV motor mode is the
only mode that can be used to control the motor.
7.13.2 SPINDLE MOTOR OPERATING MODES
The operation modes of the motor servo is controlled by
register 1 (see Table 9).
In the SAA7373 decoder there is an anti-wind-up mode for
the motor servo, selected via register 1. When the
anti-wind-up mode is activated the motor servo integrator
will hold if the motor output saturates.
7.13.2.1 Power limit
In start mode 1, start mode 2, stop mode 1 and stop
mode 2, a fixed positive or negative voltage is applied to
the motor.
This voltage can be programmed as a percentage of the
maximum possible voltage, via register 6, to limit current
drain during start and stop. The following power limits are
possible;
100% (no power limit), 75%, 50%, or 37% of maximum.
7.13.3 LOOP CHARACTERISTICS
The gain and crossover frequencies of the motor control
loop can be programmed via registers 4 and 5. The
following parameter values are possible;
Gains: 3.2, 4.0, 6.4, 8.0, 12.8, 16, 25.6 and 32
Crossover frequency f₄: 0.5 × n Hz, 0.7 × n Hz,
1.4 × n Hz, 2.8 × n Hz
Crossover frequency f₃: 0.85 × n Hz, 1.71 × n Hz,
3.42 × n Hz
It should be noted that the crossover frequencies f₃ and f₄
are scaled with the overspeed factor ‘n’ whereas the gains
are not.
7.13.4 FIFO OVERFLOW
If FIFO overflow occurs during Play mode (e.g. as a result
of motor rotational shock), the FIFO will be automatically
reset to 50% and the audio interpolator tries to conceal as
much as possible to minimise the effect of data loss.
Table 9 Operating modes
MODE
Start mode 1
Start mode 2
Jump mode
Jump mode 1
Play mode
Stop mode 1
Stop mode 2
Off mode
DESCRIPTION
The disc is accelerated by applying a positive voltage to the spindle motor. No decisions are
involved and the PLL is reset. No disc speed information is available for the microcontroller.
The disc is accelerated as in start mode 1, however the PLL will monitor the disc speed. When the
disc reaches 75% of its nominal speed, the controller will switch to jump mode. The motor status
signals selectable via register 2 are valid.
Motor servo enabled but FIFO kept reset at 50%, integrator is held. The audio is muted but it is
possible to read the subcode. It should be noted that in the CD ROM modes the data, on EBU and
the I²S-bus is not muted.
Similar to jump mode but motor integrator is kept at zero. Used for long jumps where there is a large
change in disc speed.
FIFO released after resetting to 50%. Audio mute released.
Disc is braked by applying a negative voltage to the motor. No decisions are involved.
The disc is braked as in stop mode 1 but the PLL will monitor the disc speed. As soon as the disc
reaches 12% (or 6%, depending on the programmed brake percentage, via register E) of its
nominal speed, the MOTSTOP status signal will go HIGH and switch the motor servo to Off mode.
Motor not steered.
1998 Jul 06
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