Hitachi RAS-70YH5 Service Manual page 69

9. Reset Circuit
Reset circuit performs initial setting of the microcomputer program when power is turned on.
G
Microcomputer resets program with reset voltage set to Lo, to enable operation at Hi level.
G
Fig. 9-1 shows the reset circuit, and Fig. 9-2 shows waveform at each point when power is turned on/
G
off.
After power is turned on, 12V line and 5V line voltages rise: When 12V line voltage reaches 7.2V (Zener
G
voltage of ZD201), ZD201 turns ON and Q211 and Q205 turn on, and reset voltage becomes Hi. Reset
voltage is not set to Hi until VDD of microcomputer rises to 5V, enabling operation, due to ZD201.
After power turns off, when 12V line voltage drops, ZD201 also turns OFF.
G
12
6
0
12
6
0
0305E Pg 57-82
12V
Q205
R366
C224
0V
0V
12V line
5V line
Reset voltage
77
5V
Outdoor
Microcomputer
Q212
(AX-6S00)
48
Reset
R345
0V
Fig. 9-1
12V line
5V line
Reset voltage
Fig. 9-2
– 77 –
4/1/06, 10:59 AM
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