Circuit Description - ViewSonic VE175-3-1 VS 10231 Service Manual

4. Circuit Description

1. WORKING THEOREM
A. DC-DC CONVERTER
This brick converts the 5V input voltage to 3.3V and 1.8V for controller use.
It consists of a Liner Regulator IC (AIC117), filter capacitor, and constant voltage capacitor. The AIC1117 is
a low dropout three terminal regulator with 800mA output current capability. Its low dropout voltage and fast
transient response make it ideal for low voltage microprocessor applications. Internal current and thermal limiting
provides protection against any overload condition that would create excessive junction temperatures.
B. A/D converter
The gmZAN3SL provides all the key display functions required for displaying a good quality image on a LCD
panel when connected to the PC source with analog interface. The integrated functions include a high-speed triple-ADC
and PLL, a high quality zoom and shrink scaling engine, an on-screen display (OSD) controller, digital color controls
and LVDS Transmitters. Its provides a front-end analog interface with standard VGA compliance and an output industry
standard LVDS interface for speed grade up to XGA and SXGA respectively. Typical gmZAN3SL based design need an
external 8051 equivalent MCU with integrated flash. It provides the flexibility of choosing either 8bit parallel or 6wire
host interface. Integrated LVDS transmitters and PWM based backlight control circuitry provides direct interconnect to
LCD panels and backlight inverters. Integrated Schmitt circuit, integrated reset circuit and single crystal base makes
gmZAN3XL/SL an ideal choice for the entry- level SXGA monitor design.
D. MCU:
The MTV312M micro-controller is an 8051 CPU core embedded device especially tailored for CRT/LCD Monitor
applications. It includes an 8051 CPU core, 1024-byte SRAM, 14 built-in PWM DACs, VESA DDC interface,
4- channel A/D converter, and a 64K-byte internal program Flash-ROM.
ViewSonic Corporation
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VE175-3