saa7826 NXP Semiconductors, saa7826 Datasheet - Page 27

• Manufacturer Part Number: saa7826
• Description: Cd Audio Decoder, Digital Servo And Filterless Dac With Integrated Pre-amp And Laser Control
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.15.1.4
In the CDV motor mode, the FIFO position will be put in
pulse-width modulated form on the MOTO1 pin [carrier
frequency = 300
factor]. The PLL frequency signal will be put in
pulse-density modulated form (carrier
frequency = 4.23
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.
7.15.2
The operating modes of the motor servo are controlled by
decoder register 1; see Table 12.
In the SAA7826 decoder there is an anti-windup mode for
the motor servo, selected via decoder register 1. When the
anti-windup mode is activated the motor servo integrator
will hold if the motor output saturates.
2003 Oct 01
CD audio decoder, digital servo and filterless
DAC with integrated pre-amp and laser control
S
PINDLE MOTOR OPERATING MODES
CDV/CAV output mode
d Hz; where ‘d’ is the disc speed
n MHz) on the MOTO2 pin. The
MOTO1
V4
Fig.19 Motor 4-line PWM mode application diagram.
10
V SS
27
M
+
7.15.2.1
The SAA7826 contains a servo loop that is used to
regulate the spindle speed. The motor OV flag is provided
to indicate when the motor output has overloaded. During
a large change in disc speed, i.e. by a long jump or X factor
change, the motor OV flag will be asserted due to the full
and longer duration required to attain the new desired
sped.
The OC flag indicates when the internal processes of the
modulator have overflowed and not necessarily when the
output power has reached 100%. Similarly, the flag does
not fall at a specific output power level but at a specific
speed error level. The error level at which the flag falls is
determined by the selected servo gain and will be
internally equivalent to +3
7.15.2.2
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.
100 nF
Motor OV flag
Power limit
MGA364 - 2
MOTO2
V5
gain or 3
Product specification
SAA7826
gain.