MB3771
4. 5 V and 12 V Power Supply Monitor (2 types of power supply monitor VCC1 = 5 V, VCC2 =12 V)
• 5 V is monitored by VSA. Detection voltage is about 4.2 V
• 12 V is monitored by VSB. When R1 = 390 kΩ and R2 = 62 kΩ, Detection voltage is about 9.0 V.Generally the
detection voltage is determined by the following equation.
Detection Voltage = (R1 + R2) × VSB/R2
VCC2
VCC1
MB3771
1
2
3
4
8
7
6
5
RESET
R1: 390 kΩ
R2: 62 kΩ
Logic
circuit
CT
5. 5 V and 12 V Power Supply Monitor (RESET signal is generated by 5 V, VCC1 = 5 V, VCC2 = 12 V)
• 5 V is monitored by VSA, and generates RESET signal when VSA detects voltage sagging.
• 12 V is monitored by VSC, and generates its detection signal at OUTC.
• The detection voltage of 12 V monitoring and its hysterisis is determined by the following equations.
R1 + R2 + R3
Detection voltage =
Hysterisis width =
× VSC
(8.95 V in the circuit above)
(200 mV in the circuit above)
R2 + R3
R1 (R3 - R3 // R4)
× VSC
(R2 + R3) (R2 + R3 // R4)
VCC2
VCC1
R L: 10 kΩ
MB3771
R5: 100 kΩ
R1: 390 kΩ
1
2
3
4
RESET
IRQ
8
7
6
5
or
Port Logic Circuit
R2: 33 kΩ
R4: 510 kΩ
CT
R3: 30 kΩ
9
FUJITSU [ FUJITSU ]
