MB3771_06 Datasheet, PDF (8/21 Pages) Fujitsu Component Limited. – Power Supply Monitor

MB3771
3. Arbitrary Voltage Supply Monitor
(1) Case: VCC ≤ 18 V
• Detection Voltage can be set by R1 and R2.
Detection Voltage = (R1 + R2) × VSB/R2
• Connect Pin 7 to VCC when VCC less than 4.45 V.
• Pin 7 can be opened when VCC greater than 4.45 V
Power Dissipation can be reduced.
Note : Hysteresis of 28 mV at VSB at termination is available.
Hysteresis width dose not depend on (R1 + R2).
VCC
MB3771
1
8
2
7
CT
3
6
4
5
RESET
R1
R2
(2) Monitoring VCC > 18 V
• Detection Voltage can be set by R1 and R2
Detection Voltage = (R1 + R2) × VSB/R2
• The RESET signal output is =: 0V (low level) and =: 5 V (high level). VCC voltage cannot be output.
Do not pull up RESET to VCC.
• Changing the resistance ratio between R4 and R5 changes the constant voltage output, thereby changing the
voltage of the high level RESET output. Note that the constant voltage output should not exceed 18 V.
• The 5 V output can be used as a power supply for control circuits with low current consumption.
• In setting the R3 resistance level, caution should be given to the power consumption in the resistor. The table
below lists sample resistance values for reference (using 1/4 Ω resistance).
VCC (V)
Detection
RESET Output min.
voltage (V) power supply voltage (V)
R1 (MΩ)
R2 (kΩ)
R3 (kΩ)
Output Current
(mA)
140
100
6.7
1.6
20
110
< 0.2
100
81
3.8
1.3
20
56
< 0.5
40
33
1.4
0.51
20
11
< 1.6
• Values are actual measured values (using IOUTC = 100 µA, VOLC = 0.4 V). Lowering the resistance value of R3
reduces the minimum supply voltage of the RESET output, but requires resistance with higher allowable loss.
VCC
R3
5 V output(Stablized)
R4:
100 kΩ
CT
1
8
2
7
3
0.47 µF
6
R5:
4
5
33 kΩ
RESET
R1
R2
8