Achieving both Higher
Output and Higher Speed |
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While both an increased output
transient waveform speed and an increased maximum output
drive current are required to achieve increased linear
velocities, increasing the maximum output drive current
required increasing the size of the output transistors.
However, increasing the size of the output transistors
leads to delays in the output transient waveform. Despite
this tradeoff relationship, the CXA2680ER achieves both
of the following output current performance levels.
* CD system total maximum drive current: 370 mA (figure
1) (VCC = 5V, VOP = 2.5V, T = 150°C)
* DVD system total maximum drive current: 320 mA (figure
2) (VCC = 5V, VOP = 3V, T = 150°C)
Thus this device can supply the required maximum output
drive current even under severe operating conditions
for both CD and DVD. Furthermore, in the CXA2680ER,
Sony optimized the output transient waveforms to have
both higher speed and a mirtnimal amount of overshoot
by including a built-in waveform shaping circuit. This
allows this device to support x8-speed DVD recording. |
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Read Channel Low Noise |
|
Sony's painstaking low-noise
design efforts to achieve the signal-to-noise ratio
required for higher linear speeds achieved a noise level
of 1.5 nA/√Hz (at 20 MHz, 35 mA, 20 mA p-p). |
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High-Frequency Modulator
Frequency Accuracy |
|
In high-frequency modulator,
which is used to reduce noise during playback, interference
between the return light from the disc and the laser
beam due to variations in frequency causes noise to
be aggravated. The CXA2680ER cancels frequency variations
depending on the internal resistance caused by VCO that
has the emitter junction multivibrator, thus allowing
noise to reduce. |
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DVD System Modulator
Amplitude Switching Function |
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This function allows applications
to set a modulator amplitude value that is optimal for
the DVD media used. |
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Support for a Variety
of Timing Signals |
|
The CXA2680ER provides both
differential inputs (LVDS/LVPECL) for higher speeds
and single-ended inputs (3.3 V CMOS/TTL). |
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Small Package with
Improved Heat Dissipation |
|
The CXA2680ER is provided
in a 32-pin VQFN (4.8 x 4.8 mm) miniature package that
can contribute to pickup miniaturization through reductions
in the mounting area. Not only is the package size noteworthy,
but this package can also increase the efficiency with
which heat is dissipated, since it allows the heat sink
to be cortnnected with silicon grease to the die pads,
which are exposed at the package surface. Since this
prevents heat from escaping through the PWB to the laser
diode, PWBs using this device are easy on the laser
diode. This also allows the IC to be connected at the
rear surface. |
Five-Channel Dual CD/DVD Laser Driver for Ultra Combo Drives
Vol.32