Circuit Description - ViewSonic VT2730-1M Service Manual

4. Circuit Description

A/D converter
This brick convert is the 110-220AC input voltage to 24V output for inverter use and 5V for panel ,
system and audio use and 3.3V,1.8V for controller use.
INVERTER
In order to drive the CCFLs embedded in the panel module, there is a half bridge inverter to convert by
the controller.
The input 24V up to hundreds of AC voltage output.
The inverter is formed by symmetric in order to drive the separate lamp modules.
The input stage consists of a PWM controller, half bridge inverter, and switching MOSFET to convert
DC input into AC output.
The output stage consists of a tuning capacitor, coupling capacitor, transformer, push-pull MOSFET
pair to boost AC output up to hundreds of voltage.
And one resister is serial to lamp for output voltage feedback.
There are two signal to control the inverter which come from system.
Logic "high" level which send to I901 is turn on the inverter.
BRI signal control brightness by DC level which was integral from PWM signal.
I113 Scaler MSD3003EG
The MSD3003EG is a highly integrated controller IC for LCD/PDP DTV applications with resolutions
up to full-HD (1920 x 1080). It is configured with an integrated triple-ADC/PLL, a multi-standard TV
video and audio decoder, a motion adaptive video de-interlacer, a scaling engine, the MStarACE-3
color engine, an advanced 2D graphics engine, a transport processor, a high-definition (HD) MPEG
video decoder, a 24-bit DSP for MPEG audio decoding, a DVI/HDCP/HDMI receiver, and a peripheral
control unit providing a variety of HDTV control functions.
For digital TV application, the MSD3003EG comprises an MPEG-2 transport processor with advanced
section filtering capability, an MPEG-2 (MP@HL profile) video decoder, Dolby Digital (AC-3)/MPEG
layer I and II digital audio decoder with analog audio outputs that are designed to support ATSC
HD/SDTV programs while handling ATSC CC and EPG. With additional software support, the
MSD3003EG can be used in DVB-T standard areas such as part of Asia, Africa, and Australia.
Furthermore, it is also possible to decode JPEG, MP3 formats from external sources such as USB
interfaces.
For analog TV the MSD3003EG includes NTSC/PAL/SECAM multi-standard video decoder
comprising a 3D motion adaptive comb filter and time-based correction, and a BTSC/A2/EIA-J audio
decoder to support
processor enhances video quality, motion adaptive
de-interlacer, picture quality adjustment units, and MStarACE-3 color engine.
For multimedia applications, the MSD3003EG includes an build-in MStar
interface, making it possible for the MSD3003EGto decode media (such as H.264 or MPEG-4) files via
the companion chip.
By integrating peripherals including USB 2.0 host controller, UART, IR, SPI, I2C, and PWM, the
MSD3003EG fulfills
all requirements in advanced DTV sets. To further reduce system costs, the MSD3003EG also
integrates intelligent power management control capability for green-mode requirements and
spread-spectrum support for EMI management.
PIN DESCRIPTION
VCLAMP CVBS/YC Mode Clamp Voltage Bypass H3
REFP Internal ADC Top De-coupling Pin H4
REFM Internal ADC Bottom De-coupling Pin H5
REXT Analog Input External Resister 390 ohm to AVDD_33 F4
HSYNC0 Schmitt Trigger Input w/
ViewSonic Corporation
worldwide television standards. In addition, the MStar advanced LCD TV
31
Confidential - Do Not Copy
s proprietary M-link
VT2730-1M