TDA7522 Datasheet, PDF (19/23 Pages) STMicroelectronics – Digital Servo & Decoder

TDA7522
disk motor, so the data rate changes within the capture range of the digital PLL in the Acquisition part. So
output data has no jitters that M1 buffer memory in RAM&Timing can be replaced with the shock proof
memory. (as a huge time base collector instead of M1 buffer memory).
5.7 CLV & CAV
This is a spindle motor (Disc motor) servo controller which performs Constant Linear Velocity. (CLV)
The normal velocity is about from 1.2m/s to 1.4m/s, it means disc speed is of course depending on the
location of the pick-up. When pick-up is inside of the disc, disc speed reaches about 8 rotations/sec, and
in case of outside, the speed is about 3 rotations/sec.
Mainly the CLV servo consists of 3 controllers, one is rough servo controller which controls to reach certain
speed which is within the capture range of the PLL (See Acquisition part).
The another one is frequency servo controller which controls to keep certain frequency of writing clock for
FIFO memory (M1 memory) comes from CIRC or shock proof memory controller in future.
The other one is phase servo which controls to keep certain constant phase between the writing clock and
reading clock for FIFO memory.
As long as PLL is locked, the frequency servo and the phase servo work and normally there is no overflow
or underflow of the FIFO memory. (FIFO memory works as a time base corrector).
CAV (Constant Angular Velocity) control is done by ST7 be detecting the period of eccentricity from the
disc.
5.8 Audio I/F & DAC
This block represents both of Standard Audio serial format based on Sony LSI I/F for external DAC or CD-
ROM decoder, and Audio bit stream with 1bit Delta Sigma technic for Analog stage of 1bit DAC (in
TDA7521).
The Delta Sigma block consists of functions shown in figure 7.8-1.
5.9 Disturbance detector
This block detects Focus OK, Mirror signal, Defect signals, (Shock is detected by DSP in a Tracking loop
filter, and Interruption is detected in Data Acquisition block).
These disturbance signals are used mainly in Servo block to improve the Robustness of the controller.
Mirror signal is used for Track jump with TZC (Tracking Zero Cross) signal, it is handled by ST7 and also
input to 16bit Track Up/Down counter which counts physical number of tracks during tracking Jump.
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