Hitachi RAS-E10H2 - Power Circuit Operation (Main PWB)

2
1
7
3
5
NORMAL : HI
RESET : LO
RES
Microcomputer
C524
C522
C521
R551
IC521
0V
R552
5V
MODEL RAS-E10H2
The reset circuit initializes the microcomputer program when power is ON or OFF.
Lo
w v
oltage at pin 7 resets the microcomputer and Hi activ
ates the microcomputer.
When
po
w
er
“ON”
“ON” “ON”
5V
v
oltage
r
ises
and
reaches
4.4V
,
4.4V, 4.4V
pin
1
of
IC521
is
set
to
“Hi”.
At
this
time
the
microcomputer
star
ts operation.
When
po
wer
“OFF
”
v
oltage
drops
and
reaches
4.2V
,
4.2V, 4.2V
pin
1
of
IC521
is
set
to
“Lo
w”
.
This
will
RESET
the
microcomputer
.
Power "OFF"
Power "ON"
Reset enter at 4.2V
Reset release at 4.4V
Voltage
Voltage
Voltage supply to
pin 2 of IC521
Voltage at pin 7
of microcomputer
5.0V
Fig. 1-2
Fig. 1-1
5.0V
DESCRIPTION OF MAIN CIRCUIT OPERATION
1. Reset Circuit
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