Service Manual

MM-E 2072-09333-00
2-39
c. ON/OFF Control. The ON/OFF push-button, SW26, is normally open: when pressed to turn the
Micom-Z on, it connects ground to the ON_OFF_CONT line, which turns the power supply
subsystem on the HI POWER module on.
When Micom-Z operates, the microcontroller U1 can read the status of the switch via an
inverter in U3: when the switch is pressed again, the microcontroller is alerted to the turn-off
request, and keeps the ON_OFF_CONT line at a low level by turning Q507 on via the
POW_OFF_CPU line, until it completes its shut-down routine.
d. LCD Interface. The LCD interfaces with U1 via the CPU_D0 to CPU_D7 data bus.
e. Communication with LORD module. U1 communicates with the microcomputer subsystem on
the LORD module via a serial control channel, connected to the internal UART 0.
2-6.1.2 Auxiliary Power Supply
Refer to Figure A-3.E.
The 13V8DC supply line received via the LORD module is converted to 14.7V by the DC/DC
converter comprising the pulse-width modulation (PWM) controller U6, which drives the switching
MOSFET Q2.
The resulting pulses at the secondary of T1 are rectified by CR2, and filtered by C72, C79, C83 to
obtain the 14V7 auxiliary supply voltage line.
U6 starts operating only when a high level is applied by U1 on the VLED_HEAT_EN line, to turn Q7
on.
2-6.1.3 LCD Heater and Backlighting Control
a. LCD Backlighting. The 14V7 line can be connected by Q503 to the VLED_BL_LCD line by
applying a high level on the LCD_BL_EN line, thereby turning Q505 on.
b. LCD Heating. The 14V7 line can be connected by Q1 to the VHEAT_LCD line by applying a
high level on the LCD_HEAT_EN line. This causes Q3 to cut off. U7 output falls to a low level
to turn Q1 on, thereby connecting power to the VHEAT_LCD line.
The voltage on the VHEAT_LED line is regulated by U1, using feedback from the voltage
R158, R581, R159, R167, R536: by applying a high level on the LCD_HEAT_LEVEL line,
which turns Q501 on, the voltage can be reduced, thereby reducing the heating power to the
LCD.
2-6.1.4 Keypad Lighting
The 14V7 line can be connected by Q504 to the VLED_BL_KB line by applying a high level on the
KB_BL_EN line, thereby turning Q506 on.
2-6.1.5 MIC Connector Interface
The MIC connector, P6, includes the following interface lines:
a. Serial control channel (RXD, TXD), connected directly to the LORD side connector, P3.
b. PTT_MIC line, inverted by U3 and connected to connector P3.
c. MIC_IN line, connected to connector P3.
2-6.1.6 Power Supply Subsystem
The power for the CONTROL HEAD module is provided by the 5V0 line. The +5V supply voltage is
converted by the linear regulator U4 to +3.3V on the 3V3 line.
The linear regulator U3 provides +3V to the VDD_LCD_3V0 line.