229DX-600/800APR 2002Edition 1.06.2.12 Laser Unit (LSU) Control CircuitThe laser control signals are described below.nLDENThe LSU is activated when this output signal is LOW. If an error occurs, the nLDEN output signal levelgoes High and the LSU is deactivated.nVIDEOThis is the actual Data Signal. The Laser is ON when the nVIDEO output signal level is LOW.nHSYNCThis horizontal synchronization signal transmitted from the Beam Detection Sensor sets the horizontalposition of the laser beam as it crosses the OPC Drum.nSTARTThis is the Scanner Motor Control Signal. The Scanner Motor rotates when the nSTART output signallevel is LOW.nREADYA Phased-Lock Loop (PLL) circuit keeps the Scanner Motor speed constant when the nREADY is at aLow output signal level.CLKThis is the Scanner Motor Clock.nS/HThis is the Sample Hold Signal in order to adjust the Laser power. When the Laser switches on compul-sorily, the Laser Power is adjusted to a suitable level and held until the next duty cycle in order to keepthe Laser Power stable.LaserTimingSensorScannerMotorLaserDriveCircuitScannerMotorDriveCircuitIC3SHINEnVIDEOnS/HnLDONnHSYNCnPMONLSU+5VQ24IC34IC35C190R330C189Q23Q21Q22+5VR328R326SC PCB61523CN68CN69232019nPMRYnPMCK21301632421Laser Unit Control Circuit Block DiagramR1812244321GND321321321
