Circuit Description - ViewSonic VX500PLUS-1 Service Manual

A. Interface Board
1. Power Supply (DC/DC Converter)
ICM1 is a step-down DC/DC converter that drives an external P-channel power MOSFET
(ICM2) using fixed frequency architecture. It converts a 12V DC input voltage into regulated
and stable output voltages of 5V respectively.
Pin1: 4V to 20V input supply voltage.
Pin2: Duty cycle adjustment pin.
Pin3: Logical input to shutdown the chip (Low for shutdown)
Pin4: Feedback comparator input.
Pin5: Power ground.
Pin6: Push-pull driver output to drive an external P-channel MOSFET or PNP transistor.
Pin7: Current sense comparator inverting input, not to exceed Van voltage.
Pin8: Current sense comparator non-inverting input, not to exceed Van voltage.
2. Micro-Controller
ICM10 is an 8051 embedded monitor controller (MTV312M64). It plays a major role in the
digital control of the LCD monitor. ICM10 acts as a Key control, DPMS power saving control,
auto-detect controller, and controller of ICM11 to do image process.
Pin 1 control Inverter enable or disable
Pin 2 enable vcc for panel
Pin3 send a HI signal when audio is invalid
send a LOW signal when audio is valid
Pin7 receive HI signal from ICM8 pin6 to reset
Pin9, 16,26,27,30,31,32,33 make key function operate when press key button (receive
LOW signal from key button.)
Pin13, 14 communicate with ICM9 (EEPROM) by I
Pin17, 18,20,21,22,23 communicate with ICM11 (scalar) by 6-wire protocol
Pin19 detect audio in
Pin28, 29 do ISP (in-system program)
ViewSonic Corporation
5.

CIRCUIT DESCRIPTION

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VX500+-1