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4 Circuit Description
A. DC-DC CONVERTER AND LDO
This brick converts the 12V input voltage to 5V for panel use and U9
converts
the voltage from 5V to 3.3V ,U8 convert
s
the
voltage from 5V to 2.5V for controller use.
It consists of a PWM IC (LM2596), flywheel Diode (D4), buck choke (L1), and capacitor (C68,C69).
U7 (LM2596) is a PWM generator working at 150Khz.
Self protection features include a t
wo
stage frequency reducing current limit for the output switch and an over temperature
shutdown for complete protection under fault condition.
U8 is a low dropout voltage and fast trasient response three terminal regulator,
the
output voltage is 2.5V fixed.
U9 is a low dropout voltage and fast trasient response three terminal regulator,
the
output voltage is 3.3V fixed.
B. Scaling controller
The gm2121 is a graphics processing IC for Liquid Crystal Display (LCD) monitor at SXGA resolution . It provides a
high-speed
triple-ADC and PLL,a high quality zoom and shrink scaling engine , an on-screen display (OSD) controller,
digital color controls,
an on-chip micro-controller ( OCM ) and industry standard dual four channel LVDS transmitter for
direct connect to LCD panel
with LVDS interface.
The triple-ADC is to convert RGB analog signal to digital signal. The gm2121 is a complete 8-bit up to 162MHz
(SXGA 75Hz /
UXGA 60Hz) monolithic analog interface optimized for capturing RGB graphic signal, +3.3V and +2.5V
power supply is
necessary.
The gm2121 scaling filter can combine it’s advanced scaling with a pixel-replication type scaling function.this is useful for
improving the sharpness and definition of graphics when scaling at high zoom factors. Gm2121 provides an 8 to 10 bit
look-up
table (LUT) for each input color channel intended for Gamma correction and to compensate for a non-linear
response of the LCD
panel . A 10-bit output results in an improved color depth control. The 10-bit output is then dithered
down to 8 bits( or 6 bits) per
channel at the display .
C. AMP
The APA4835 is a monolithic integrated circuit , which provides DC volume control , and a stereo bridged audio power
amplifiers
capable of producing 2W (2.2W) into 4
Ω
with less than 10% (1.0%) THD+N. APA4835 includes a DC volume
control , stereo
bridge-tied and single-ended audio power amplifiers , stereo docking outputs , and a selectable gain control,
that makes it
optimally fittable for notebook PC, multimedia monitors , and other portable applications.
5
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