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

5 V Circuit
DC/DC converter MAX608ESA (IC105) generates +5.11 V and it makes up 5 V system.
VIO : +5 V source for 3-pin jack and LCD power block.
BATDTCT: It distinguishes alkaline and Li-ion to change the load according to the battery. When
alkaline is used, it is H. When Li-ion, it is L.
P5V : Controls ON/OFF of DC-DC converter (IC105). From pin 166 of MB87A915.
V3SYS
BATDTCT
SW3
Alkaline = OPEN
Li-ion = CLOSE
F101
Primary Circuit
SHDN
MAX608 (IC105)
Q107
Changeover circuit for loading
Q104
IC104
L101
L102 D105
Q109
EXT
CS
— 36 —
BATDTCT = OPEN
Q104 ON
D104
IC104 OFF
BATDTCT = CLOSE
Q106
Q104 OFF
IC104 ON
VI0
P5V
Load: Min.
Load: Max.