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7 Special Circuit Descriptions
SAM4S ER-5200 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(U13). When
+5VDC is fallen under 4.3Vdc by Power-off, reset signal prohibits the system from miss-operation by lowering down
to 0V.
Figure 7-2 Reset and Power Fail Waveform (Power On and Off)
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 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
Figure 7-3 Power Fail Detect Circuit
VCC
nRESET
P_FAIL
VDRV(24V)
VCC
nRESET
P_FAIL
VDRV(24V)
200ms
26ms
4.3V
14V
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