February 2003
FM1233D
3-Pin µC Supervisor Circuit
General Description
Features
The FM1233D 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 5V systems with different
tolerances.
Precision monitoring of 5V and lower voltage microprocessor
systems
V values of 4.62V, 4.38V and 4.12V
TH
Automatic restart of microprocessor after power failure
140ms (min) power-on RESET delay (typ.: 256ms)
Internal 5kΩ pull-up resistor
The device features a precision temperature-compensated volt-
age reference and comparator. When V falls to the threshold
CC
Other reset choices available: 32 to 128ms
Operating Temperature -40°C to +105°C
SOT23-3 package
voltage, a RESET pulse is issued, holding the output in the
active state. When power rises above V , the reset remains for
TH
approximately 250 ms to allow the system clock and other cir-
cuits to stabilize. The reset output of FM1233D is of open-drain
active low type.
Typical Operating Circuit
VCC
3
FM1233D
Controller
1
2
RESET
GND
Connection Diagram
1
2
GND
3
VCC
FM1233D
RESET
SOT23-3 Package
©2002 Fairchild Semiconductor Corporation
FM1233D Rev. D
1
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