Display Circuit - Kenwood TS-590SG Service Manual

Display Circuit

The Display unit (XC1-022) consists of the panel MCU
(IC103) and the peripheral circuits, LCD display, and LED
including LCD backlight. Communication with the main
MCU (XC1-021 IC306) is carried out in PTXD, PRXD, PCTS,
PRTS. (Transmission speed: 115200bps)
n Circuits around the panel MCU
The 33C power supply (3.3V) sent from the transceiver is
used as the power supply for the digital portion. The panel
MCU clock is 11.0592MHz (X101). The reset signal is con-
trolled from the main MCU. Also, the panel MCU accepts
the key matrix, various encoders, and volume.
LCD
COM1~COM3
S1~S119
IC101
LCD driver
Key matrix
CIRCUIT DESCRIPTION
8A (8V)
LCD backlight
(Amber)
Q101/Q103
IC102
Drive circuit
Buffer
for Amber
DIMM
LCDB_Y
5C_L (5V)
LCDB_YG
Q102
Power supply
control
DATA/CLK/CE
IC103
KIN0~KIN7
Panel MCU
KO0~KO7
11.0592MHz
Fig. 15 Display circuit
n LCD driver
The LCD driver used is LC75897PW (IC101). In accor-
dance with the IC's specifi cation, the 5V power supply for
the LCD needs to be input after VDD (3.3V), a power supply
switch circuit (Q102) for turning 5V ON after 3.3V occurs.
In order to reliably control the power ON sequence, such
control is executed by the panel MCU. (Frame frequency:
97.66Hz, duty: 1/3, bias: 1/3)
n LED
LCD backlight uses 54 LEDs for 1 color, and 10 grada-
tions of color between amber and green can be chosen
from the menu. There are 7 steps of the back light lumi-
nance: 6 steps with the dimmer and OFF. Because the drive
transistors (Q101, Q103, Q104, Q105) cannot be directly
controlled with the panel MCU because of the quantity of
LEDs, logic ICs (IC102, IC104) are used as a buffer. LCD
backlight's default value is amber. LED at times of transmit/
receive is controlled by the panel MCU.
LCD backlight
(Green)
Q104/Q105
IC104
Drive circuit
Buffer
for Green
IC105
Voltage converter
IC106
Voltage converter
MU/MD/PCTS/PRXD/PRTS/
PTXD/BKC/PRESET/PWS
TS-590SG
Main Encoder
RIT Encoder
Multi Encoder
Lo/Hi Encoder
Notch VR/SQL VR
AF VR/RF VR
CN107
to Control unit
XC1-021 (A/3)
19