7 Special Circuit Descriptions
SAM4S ER-380M/F SERIES 7-3
7-2 RESET and Power Fail Circuit
7-2-1 Reset Circuit
Reset signal is a signal in order to start-up CPU under Power-on. Reset circuit uses a reset IC M51953B(U8). When
+5VDC is fallen under 4.3Vdc by Power-off, reset signal prohibits the system from abnormal operation by lowering
down to 0V.
7-2-2 Power Fail Detect Circuit
Power Fail Sensing Circuit detects sudden power-off to backup the needed data and current CPU status into RAM
before 35ms just before +5V drops. When power is turned on, the CPU does the operations which were working
before power-off. This system is designed to sense the time when the AC Line voltage is goes down to 89Vac(USA)
or 170Vac(Europe) . That is, when +24Vdc goes down to +14Vdc.
The waveform of power fail signal refer to Figure 7-2
V68
INT0_PFAIL
1uF
C77
50V
3.3K
R88
2.7K
R93
VDRV VCC
Isink = Typ.18m A
1
8
4
3
2
LM 393D
U 17:1
VCC VCC VCC
12K
R97
6.8K
R98
C85
100nF
C84
100nF
4.7K
R99
4.7K
R 100
R 101
4.7K
Figure 7-2 Power Fail Detect Circuit
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