Power Supply Circuit; Primary Circuit - Casio CASSIOPEIA A-20 Service Manual & Parts List

POWER SUPPLY CIRCUIT

The power supply circuit consists of 5 blocks which are Primary circuit, 5 V circuit, 3 V circuit , PCMCIA
power circuit and LCD power circuit as follows;
Alkaline
Li-ion
AC Adapter

Primary Circuit

The voltages from both batteries, alkaline and Li-ion, apply to V5 and V3 circuits through the fuse when the
batteries is loaded.
CHGDTCTB is for Li-ion detect. When Li-ion is full charged CHGDTCTB becomes L.
ACDTCTB is for AC adapter detector. It detects whether AC adapter is used or not. When AC adapter is
used ACDTCTB becomes L.
Alkaline Li-ion
(1.6 ~ 3.4 V) (3.0 ~ 3.6 V)
AC Adapter
Fuse
Primary
circuit
F100
D100
L100
5V circuit
3V circuit
Lithium
CHGDTCTB (to MB87A915)
D101
Q127
D102
C105
— 35 —
PCMCIA
PCMCIA
power circuit
5 V system
LCD
LCD
power circuit
3 V system
To Detector (VSUB)
F101
To 3V and V5 circuits.
ACDTCTB (to MB87A915)