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8.1
Inverter Board Circuit
The diagram of inverter board circuit is shown in Appendix (PWB-0420_01). The inverter
supplies power for backlight for the LCD panel.
8.2
Power supply Board Circuit
Please refer to 2.0 power Schematic sheet in Appendix. The 12Vdc from adaptor output is fed into
J800 as power regulation of U801 (BA9741F) input power and inverter main power on pin 1 of
CN830. The U801 can provide two independent power sources: a) The 5Vdc will be for main
board power. ; b)
A
nother 10.5Vdc will output as audio power when audio
Jack
is inserted.
8.3
Scaling controller Board Circuit
The Scaling IC U400 is to convert the input signal from VGA, and
SV
GA to a
n
XGA
resolution that
the
panel can acknowledge.
The scaling IC of gm2115 is a highly integrated System-on-a- Chip with very powerful functions,
including integrated 8 bit triple-channel ADC/PLL, programmable OnPanel timing controller,
embedded microcontroller with parallel ROM interface, OSD engine, sRGB compliance, and
PWM back light intensity control.
The Scaling IC features an integrated timing controller (TCON) that connects directly to
commercially available row and column drivers. All TCON signals OCLK, ECK, ORGB, ERGB,
OSP, ESP, OPOL, OINV, EINV on pin 119 to pin 128 of U400 have programmable drive strengths
and can be disabled to control Panel.
The flash memory chip of U410
contains
codes via parallel data bus interface to
communicate with Scaling IC U400.
The DDC memory chip of U300
stores
DDC data and the NVRAM chip store
s
timings and
setting data. Since the NVRAM has to get series number information from DDC chip, both
their
SDA and SCL ports
are
connected together
. In order
to avoid conflict on I2C interface
during the
DDC data
transfer,
the electrical switching of U301
is isolated and controlled by scaling IC pin
GPIO7.
8.4
Audio Circuit
Please refer to section 7, sound AMP Schematic. The audio Right/Left channels are fed
into pin
6 /8 of sound AMP U701 (AN7522) while Audio plug is inserted
i
n J701 jack. The sound
output
amplitude will depend on this bias voltage on pin 9 of U701, which is always controlled by
Q702.
When mute is activated, the Q703 will be forced to saturation to block sound output.
When standby
is activated, the Q705/Q704 will also go to saturation to bypass the sound
input signal to ground.
The sound outputs of U701 will drive speakers via CN701 connecter.
7
.
T
HEORY OF OPERATION
ViewSonic Corporation
15
VG500b-1
Confidential
– Do Not Copy
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