©2003 Fairchild Semiconductor Corporation
1
www.fairchildsemi.com
February 2003
FM1233E 3-Pin µC Supervisor Circuit
FM1233E Rev. D
FM1233E
3-Pin µC Supervisor Circuit
General Description
The FM1233E is a supervisor circuit that monitors a micropro-
cessor power supply or other system voltage and issues a reset
pulse when a fault condition exists. Several different threshold
voltages are offered to accommodate 3V systems with different
tolerances.
The device features a precision temperature-compensated volt-
age reference and comparator. When V
CC
falls to the threshold
voltage, a RESET pulse is issued, holding the output in the
active state. When power rises above V
TH
, the reset remains for
approximately 250 ms to allow the system clock and other cir-
cuits to stabilize. The reset output of FM1233E is of open-drain
active low type.
Features
■
Precision monitoring of 3.3V and lower voltage
microprocessor systems
■
V
TH
values of 2.88V, 2.72V
■
Automatic restart of microprocessor after power failure
■
140ms (min) power-on RESET
delay (typ.: 256ms)
■
Internal 5k
Ω
pull-up resistor
■
Other reset choices available: 32 to 128ms
■
Operating Temperature -40°C to +105°C
■
SOT23-3 package
Typical Operating Circuit
Connection Diagram
SOT23-3 Package
1
FM1233E
Controller
2
3
V
CC
GND
RESET
GND
V
CC
RESET
1
FM1233E
2
3
