saa7826 NXP Semiconductors, saa7826 Datasheet - Page 9

• 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
7.1
The SAA7826 removes the need for an external diode signal pre-amplifier.
A simplified diagram of the HF data path is illustrated in Fig.3. The high-pass filter, equalizing filter, HF gain and adaptive
slicer are all register programmable, thus enabling the SAA7826 to be optimized for the intended application.
7.2
7.2.1
The decoding part supports a full audio specification and
can operate at single-speed (n = 1), double-speed (n = 2)
and quad-speed (n = 4). The factor ‘n’ is called the
overspeed factor. A simplified data flow through the
decoder part is illustrated in Fig.7 for the M0 version and
Fig.8 for the M1 version.
7.2.2
The SAA7826 is a 1 , 2 and 4 (three-speed) decoding
device, with an internal Phase-Locked Loop (PLL) clock
multiplier. Table 1 gives the playback speeds that are
achievable in conjunction with crystal frequency, the
mechanism and internal clock settings (selectable via
decoder register B).
2003 Oct 01
handbook, full pagewidth
CD audio decoder, digital servo and filterless
DAC with integrated pre-amp and laser control
FUNCTIONAL DESCRIPTION
Data acquisition and HF data path
Decoder part
P
D
d1_hf
d2_hf
d3_hf
d4_hf
hf_gain 5:0
RINCIPLE OPERATING MODES OF THE DECODER
ECODER SPEED AND CRYSTAL FREQUENCY
high-pass filter
Fig.3 Simplified block diagram of the HF data path and adaptive slicer.
V ref
op-amp
op-amp
summing amplifier
op-amp
9
V ana
7.2.3
For electronic shock absorption applications, the SAA7826
can be put into lock-to-disc mode. This allows Constant
Angular Velocity (CAV) disc playback with varying input
data rates from the inside to the outside of the disc.
In the lock-to-disc mode, the FIFO is blocked and the
decoder will adjust its output data rate to the disc speed.
Hence, the frequency of the I
clocks are dependent on the disc speed. In the lock-to-disc
mode there is a limit on the maximum variation in disc
speed that the SAA7826 will follow. Disc speeds must
always be within 25% to 100% range of their nominal
value. The lock-to-disc mode is enabled or disabled by
decoder register E.
equalising
L
bypass
filter
OCK
-
TO
-
DISC MODE
comp
adaptive slicer
2
S-bus (WCLK and SCLK)
67.7 MHz
THRESHOLD
CONTROL
Product specification
SAA7826
sliced
data
MBL438