Circuit Description Of Operation Panel Pwb - Sharp FO-4450 Service Manual

FO-4450U/FO-CS1

[5] Circuit description of operation panel PWB

1. Operational description
1) Operation panel PWB
The operation panel PWB includes the ten key scan circuit and the LED
lighting circuit. The LS145 is controlled through LD0~LD3 (4 bits) and
ten key detection is performed. The HC174 is controlled through
LD0~LD5 (6 bits) to provide LED lighting information.
2) COG(LCD) (LMG2025-TPR)
The COG uses the one-chip LCD driver IC to display 20 digits x 2 lines.
The LCD display density is controlled with an external resistor.
2. Block diagram
SENB
SEN[7.0]
LD[7.0]
LEDEN1
LEDEN2
RS
R/XW
E
PAGE PLATE SW
KEY MATRIX
LD[3.0]
LS145
LD[5.0]
AHCT174
LD[5.0]
AHCT174
LD[7.0]
JOINT PWB
LED PWB
+5V
+5V
Fig. 10
5 – 18
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COG(LCD)
(2 LINES)