MB3771
11. Low Voltage and Over Voltage Detection (VCC = 5 V)
VSH has no hysteresis. When over voltage is detected, RESET is held in the constant time as well as when
low voltage is detected.
VSL = (R1 + R2) × VSB/R2
VSH = (R3 + R4) × VSC/R4
VCC
R3
R4
R1
R2
MB3771
RESET
1
2
3
4
8
7
6
5
RESET
CT
VCC
VSL
VSH
12. Detection of Abnormal State of Power Supply System (VCC = 5 V)
• This Example circuit detects abnormal low/over voltage of power supply voltage and is indicated by LED
indicator. LED is reset by the CLEAR key.
• The detection levels of low/over voltages are determined by VSA, and R1 and R2 respectively.
VCC
LED
R1
MB3771
R3: 620 Ω
CLEAR
1
2
3
4
8
7
6
5
R4:
1 kΩ to 100 kΩ
R2
13
FUJITSU [ FUJITSU ]
