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4. Circuit Description
4.1 Inverter Board Circuit
The diagram of inverter board circuit is shown in Appendix (PWB-0538). The inverter supplies power for
backlight for the LCD panel.
4.2 Power supply Board Circuit
Please refer to power Schematic sheet in Appendix. The 12Vdc from adaptor output is fed into J800 as
power regulation of U801 (AO4403) 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) The another 10.5Vdc
will output as audio power at when audio jet is inserted.
4.3 Scaling controller Board Circuit
The Scaling IC U005 is to convert the input signal from VGA, SXGA and UXGA to a SXGA resolution that
panel can acknowledge.
The scaling IC of MRT MASCOT V2 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 68 to pin 79 of U005 have programmable drive strengths and can be disabled to control Panel.
The flash memory chip of U001 contains codes via parallel data bus interface to communicate
with Scaling IC U005.
The DDC memory chip of U004 stores DDC data and the NVRAM chip stores timings and setting data.
Since the NVRAM has to get series number information data from DDC chip, both their SDA and SCL
ports connected together. In order to avoid conflict on I C interface during the DDC transfer from U004,
the electrical switching of U009 is isolated and controlled by scaling IC pin GPIO7.
4.4 Audio Circuit
The audio Right/Left channels are fed into pin 6 /8 of sound AMP U701 (AN7522) while Audio plug is
inserted on 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 sound outputs of U701 will drive speakers via CN701 connecter.
ViewSonic Corporation
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Confidential – Do Not Copy
VG500-2
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