Circuit Description - ViewSonic VP201b-1 Service Manual

4. Circuit Description

4.1 Power supply (DC/DC Converter):
4.1.1 IC251 BA9741 is a switching regulator controller that uses a PWM method. It is used for DC to
DC step-down conversion. It converts 24V DC into regulated and stable output voltages of 18V
and 5V.
4.1.2 Regulator:
IC252 converts 5V into regulated and stable O/P 3.3V.
IC253 converts 5V into regulated and stable O/P 1.8V
IC255 converts 5V into regulated and stable O/P 3.3V.
IC256 converts 5V into regulated and stable O/P 2.5V.
4.2 DDC data select:
4.2.1 IC601 (AT24C02) saves D-SUB DDC data.
4.2.2 IC604 (AT24C02) saves DVI-D, DDC data.
4.2.3 IC605 (AT24C02) saves DVI-A, DDC data.
4.3 D-sub and DVI-A signal select
The VP201s is equipped with two analog signal inputs: D-sub and DVI-A. The user may only choose to
display the signal from one of these ports: D-sub or DVI-A.
IC607 (AD8186) is a R, G, B signal switch IC. If the control signal (RGBSEL) is high, the device will
display the DVI-A signal. If the control signal (RGBSEL) is low, the device will display the D-sub.
4.4 Scalar
The gm1601H is a dual channel graphics and video processing IC for Liquid Crystal Display (LCD) monitors and
televisions incorporating Picture in Picture, up to WUXGA output resolutions. The gm1601H provides all key IC
functions required for image capture, processing and display timing control. On-chip functions include a high speed
triple-ADC and PLL, Ultra-Reliable DVI receiver, high quality zoom, and shrink scaling engines, Motion Adaptive
De-interlacing (MADI), Low Angle Diagonal Interpolation (LADI), an on-screen display (OSD) controller, a 100MHz
on-chip X186 micro-controller (OCM), and a selectable double side TTL or dual channel LVDS transmitter for
interface to displays.
4.5 USB(VP201s/b only)
IC951(USB20H04) is a 4-Port USB 2.0 Hub controller. It is compliant with the USB 2.0 specification,
enables bus-powered Hi-Speed hub design, and is compatible with On-The-Go (OTG) USB devices. It is
equipped with a serial interface for configuration from EEPROM or micro-controller when the default
settings are not used. Includes integrated termination and pull-up/pull-down resistors, as well as internal
short circuit protection of DP and DM lines. Supports individual or ganged
over-current protection and power control.
ViewSonic Corporation
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VP201b/s-1