MB3773 Fujitsu, MB3773 Datasheet - Page 16

• Manufacturer Part Number: MB3773
• Description: Power Supply Monitor with Watch-Dog Timer
• Manufacturer: Fujitsu

16
MB3773
These are example application circuts in which the MB3773 monitors supply voltage alone without resetting
the microcomputer even if the latter, used in standby mode, stops sending the clock pulse to the MB3773.
•The watch-dog timer is inhibited by clamping the Cr pin voltage to V
The supply voltage is constantly monitored even while the watch-dog timer is inhibited.
For this reason, a reset signal is output at the occurrence of either instataneous disruption or a sudden drop
to low voltage.
Note that in application examples a and b, the hold signal is inactive when the watch-dog timer is inhibited
at the time of resetting.
If the hold signal is active when tie microcomputer is reset, the solution is to add a gate, as in examples c and d.
a Using NPN transistor
b Using PNP transistor
C
C
V
V
T
EXAMPLE 8 : Stopping Watch-dog Timer (Monitering only supply voltage)
T
CC
CC
(5V)
(5V)
1
2
3
4
1
2
3
4
MB3773
MB3773
8
7
6
5
8
7
6
5
R
R
2
2
=1k
=1k
R
R
1
1
=1M
=51k
REF
.
RESET
RESET
CK
RESET
RESET
HALT
HALT
CK
GND
GND
Logic circuit
Logic circuit
(Continued)