SAA7370 Datasheet, PDF (9/60 Pages) NXP Semiconductors – Digital servo processor and Compact Disc decoder CD7

Philips Semiconductors
Digital servo processor and
Compact Disc decoder (CD7)
Product specification
SAA7370
2. Data capture performance is not optimized for these
options.
7.2 Crystal oscillator
The crystal oscillator is a conventional 2 pin design
operating between 8 MHz and 35 MHz. This oscillator is
capable of operating with ceramic resonators and with
both fundamental and third overtone crystals. External
components should be used to suppress the fundamental
output of the third overtone crystals as shown in Figs 3
and 4. Typical oscillation frequencies required are 8.4672,
16.9344 or 33.8688 MHz depending on the internal clock
settings used and whether or not the clock multiplier is
enabled.
SAA7370
OSCILLATOR
7.3 Data slicer and clock regenerator
The SAA7370 has an integrated slice level comparator
which can be clocked by the crystal frequency clock, or
8 times the crystal frequency clock (if SELPLL is set HIGH
while using an 8.4672 MHz crystal, and register 4 is set
to 0xxx). The slice level is controlled by an internal current
source applied to an external capacitor under the control
of the Digital Phase-Locked Loop (DPLL).
Regeneration of the bit clock is achieved with an internal
fully digital PLL. No external components are required and
the bit clock is not output. The PLL has two registers
(8 and 9) for selecting bandwidth and equalization.
For certain applications an off-track input is necessary.
This is internally connected from the servo part (its polarity
can be changed by the foc_parm1 parameter), but may be
input via the V1 pin if selected by register C. If this flag is
HIGH, the SAA7370 will assume that its servo part is
following on the wrong track, and will flag all incoming HF
data as incorrect.
CROUT
8.4672 MHz
CRIN
MBG420
330 Ω
100 kΩ
22 pF 22 pF
Fig.3 8.4672 MHz fundamental configuration.
SAA7370
OSCILLATOR
CROUT
CRIN
33.8688 MHz
MBG419
330 Ω
100 kΩ
10 pF 10 pF
3.3 µH
1 nF
Fig.4 33.8688 MHz overtone configuration.
1998 Feb 26
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