tza1020 NXP Semiconductors, tza1020 Datasheet - Page 7

• Manufacturer Part Number: tza1020
• Description: Pre-amplifiers For Cd-rw Systems
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7
All functions are designed in such a way that a read speed
up to twelve times nominal speed is possible
(N = 1, 2, 4, 8 or 12). Recording speed up to four is
possible (N = 1, 2 or 4). The maximum recording speed
must be determined.
7.1
The central diodes currents (C1 to C4) are fed to a high
bandwidth current amplifier. The gain of the current
amplifier can be switched by means of the I
microcontroller interface to compensate for differences in
CD-R and CD-RW disc reflection. Data signals up to
twelve times nominal data speed can be read.
7.2
The currents from the central diodes (C1 to C4), the
current from the satellite diodes (SA1, SA2, SB1 and SB2)
and the laser set-point current (CAGAIN) are (optionally
sampled) fed to the first low-pass filters with a bandwidth
of 60 kHz. The normalizing circuit generates error signals
for servo control that are independent of the diode current
level. The gain of the error signals is controlled by the
I
becomes active if the input current level is below a certain
threshold value. This threshold value is also controlled by
the I
7.3
The wobble signal of the pre-groove is detected by means
of the PPN signal. The currents from inputs C1 to C4 are
filtered and processed to provide optimal signal-to-noise
ratio. The bandwidth of the filter may be adapted to the
disc speed via the I
reduction loop is controlled by an external capacitor, the
I
processor.
2000 Oct 30
2
2
C-bus microcontroller interface. A dropout concealment
C-bus interface controls the total operation of the
Pre-amplifiers for CD-RW systems
FUNCTIONAL DESCRIPTION
2
C-bus.
Data amplifier
Normalizer
Wobble pre-processor
2
C-bus. The bandwidth of a noise
2
C-bus
7
7.4
The beta detector generates signals necessary for the
symmetry detection of the HF signal. By measuring peak
values (A1 and A2) and average value of the signal
(CALF), an optimum laser writing power can be
determined. The gain of the measured values is controlled
by the I
and bandwidth of the low-pass filtered aperture signal can
also be adapted to the disc speed by the I
7.5
The alpha detector determines a parameter called ‘alpha’
during disc writing. Alpha must be kept constant to allow
recording over a fingerprint or black dot. The definition of
alpha is different for CD-R and CD-RW; for CD-R the light
absorption of the disc is measured, for CD-RW alpha is
determined by actual laser power and disc reflection. The
gain of the measured signals and the CD-R and CD-RW
selection is performed by the I
7.6
The fast track count circuit generates a Radial Error (RE)
signal for fast track counting. A gain switch compensates
for difference in CD-R and CD-RW disc reflection.
7.7
To allow alignment of photo diodes via the TZA1020, a
number of linear combinations of input currents can be
realized (MEAS1 and MEAS2). Selection of the actual
combination is performed by the I
Beta detector
Alpha detector
Fast track count
Spot position measurement
2
C-bus. The time constant of the peak detectors
TZA1020; TZA1020A
2
C-bus.
2
C-bus.
Product specification
2
C-bus.