Lsu Drive Circuit - Toshiba DP120F Service Manual

3.3 LSU Drive Circuit

07-03-03
Fig. 7-3-3
The LSU (Laser Scanner Unit) drive circuit consists of the PTC GA (IC45), EET (IC39), PIX-
DRAM (IC25), and other peripheral devices. It controls the LSU connected to CN12 on the
MOTHER PBA to apply a laser beam to the drum.
The PTC GA divides the clock of the PTCCK2 signal output from the inch-based crystal osillator
(X5) or the PTCCK1 signal output from the milli-based crystal osillator (X6) by the external
circuit and program processing to output a PMCLK signal. The I/OP-2 GA causes the PMTON
signal to go HIGH and drives the polygon motor with the timing of the PMCLK signal.
The polygon motor in the LSU causes the PMTSTS signal to go HIGH and outputs it to the PTC
GA when the timing of the PMCLK signal synchronizes with the rotation.
The PTC GA stands by from the moment when the polygon motor begins to be driven to the
moment when the speed is stabilized and then detects the PMTSTS signal. If the PMTSTS
signal is HIGH at this moment, the PTC GA causes the LEN signal to go HIGH and enables the
LSU to output a laser beam.
The PTC GA reads the image data stored in the DRAM where it is converted to a LDATA signal
and outputs it to the EET.
The EET performs smoothing on LDATA and converts it to VDIN before outputting it to the PTC
GA.
DP120F/DP125F Circuit Description 7-32 March 2000 © TOSHIBA TEC