LADIC
The Laser Drive IC, LADIC, controls the data to
the lasers, and the supply to them. It performs
three main functions:
· It drives the laser for both playback and
record functions. Its greatest stress is real-
ized during record, producing data signals
and write pulses. The recording process is
flexible with respect to the input modulation
method (EFM, EFM+, 17 pp, etc.). This is
necessary to support CDR/RW and
DVDR/RW. To accomplish this, the LADIC
uses two Random Access Memories (RAM)
which can be loaded (non real-time) via the
I
2
C Bus from the microcontroller.
· It drives the laser with a sequence of pro-
grammable write pulses with high timing
accuracy and high peak current levels.
· It controls the exact light power levels coming
from the laser and controls the exact power
absorbed by the disc during recording.
The LADIC needs three independent power
supplies. These are the analog and digital power
supplies, and V Bias for the laser driver function.
The supplies are separate to obtain maximum
output performance where there are large and
highly dynamic current flows.
The LADIC is controlled by an I
2
C bus. The
laser is operated at three current levels:
Playback, Record and Erase. During the initi-
lazation of a disc to be recorded on, and test
recording is preformed in a special place on the
the inner most section of the disc. A series of
random data is recorded with a wide range of
current levels. The data is played back. Two
feedback signals are generated and sent to the
MACE3 circuit, A1 and A2. A second Fine tuning
of the Optimal Laser Current is preformed. The
disc is written to again except the current range
is chosen by the MACE3 using the feedback
received. This fine tuning of the laser current
produces the Calf feedback signal that is sent to
the MACE3 and it is stored in the MACE3’s oper-
ating RAM.
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