Lcd Power Circuit - Casio CASSIOPEIA A-20 Service Manual & Parts List

LCD power Circuit

DC/DC converter RN5VH3 (IC201) generates LCD power and it makes up LCD power system for LCD.
VDD : +3.7 V source for LCD unit.
VAMP : +7.0 V source for LCD unit.
PLCD : Controls ON/OFF of VAMP. From pin 159 of MB87A915 (IC3).
VLCD+: +15.5 V source for LCD unit.
VTH : LCD power source for LCD unit.
EVOL 0-3 : LCD status.
P25ON : Controls ON/OFF of LCD power. From pin 167 of MB87A915 (IC3).
VLCD- : -10.0 V source for LCD unit.
ONSTATUSB : Controls ON/OFF of LCD power. From pin 99 of CPU (IC1).
Q200
V3MAIN
+
+
Q201
L219
Q202
Q203
VDD
SCI7660
(IC200)
CAP+
V0
D200
VDD
RV5 VH3
(IC201)
EXT1
EXT2
FB1
CSW
D203
Q204
— 39 —
VDD
VAMP
PLCD
VLCD+
VTH
TC74HC4066 (IC202)
EVOL 0
1IO 1C
2C EVOL 1
1OI
EVOL 2
3C
2IO
EVOL 3
4C
2OI
3IO
3OI
4IO
4OI
P25ON
VLCD-
ONSTATUSB
Q205