FUJITSU MB3773 - Manual (Page 17)

MB3773
17
EXAMPLE 6: Monitoring Low voltage and Overvoltage Monitoring (with hysteresis)
V CC (5 V)
1
2
3
4
8
7
6
5
MB3773
RESET
RESET
CK
GND
Comp. 2
Example : Comp. 1, Comp. 2
: MB4204, MB47393
20 k
Ω
R
6
_
+
180 k
Ω
R
4
30 k
Ω
R
3
5.6 k
Ω
R
6
1.2 k
Ω
R
1
4.7 k
Ω
R
5
Comp. 1
Notes :
•
Comp. 1 and Comp. 2 are used to monitor for overvoltage while the MB3773 is used to monitor
for low voltage. Detection voltages V
1L
/V
1H
at the time of low voltage are approximately 4.2 V/4.3 V.
Detection voltages V
2L
/V
2H
at the time of overvoltage are approximately 6.0 V/6.1 V.
For the formulas for finding hysteresis width and detection voltage, see EXAMPLE 4.
•
Use V
CC
(
=
5 V) to power the comparators (Comp. 1 and Comp. 2) in the external circuit shown
above.
Logic circuit
Diode
RESET
0 V
1L
V
1H
V
2L
V
2H
V
CC
+
_
C
T