FUJITSU MB3773 - Manual (Page 16)

MB3773
16
EXAMPLE 5: Monitoring Two Supply Voltages (with hysteresis and reset output)
V
CC 1
(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
+
_
+
_
V
CC2
(12 V)
180 k
Ω
R
4
30 k
Ω
R
3
5.1 k
Ω
R
2
1.2 k
Ω
R
1
4.7 k
Ω
R
5
Comp. 1
Notes :
•
When either 5 V or 12 V supply voltage decreases below its detection voltage (V
SL
),
the MB3773 RESET terminal is set to High and the MB3773 RESET terminal is set to Low.
•
Use V
CC1
(
=
5 V) to power the comparators (Comp. 1 and Comp. 2) in the external circuit shown
above.
•
The detection voltage of the V
CC2
(
=
12 V) supply voltage is approximately 9.2 V/9.4 V and has a
hysteresis width of approximately 0.2 V. For the formulas for finding hysteresis width and detection
voltage, see section 4.
Logic circuit
Diode C
T