FMFFM1233AC Datasheet, PDF (1/7 Pages) Fairchild Semiconductor – 3-Pin uC Supervisor Circuit

September 2004
FM1233A
3-Pin µC Supervisor Circuit
General Description
The FM1233A 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 3.3V and 3.0V systems
with different tolerances.
FM1233A 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
asserted for a minimum period (t_RST) to allow the system clock
and other circuits to stabilize. The reset output of FM1233A is of
open-drain active low type.
The FM1233A also can monitor a switch closure on its output,
enabling it to recognize an external reset from a pushbutton
switch or a µP. In the case of a switch, the closure will be
debounced by circuitry internal to the FM1233A.
Features
■ Precision monitoring of 3.3V and lower voltage
microprocessor systems
■ V_TH values of 3.08V, 2.88V and 2.72V
■ Automatic restart of microprocessor after power failure
■ Reset Timeout Period Choice:
– Options AC and AD: 140ms (min)/256ms (typ)
– Option ABA: 17ms (min)/32ms (typ)
– Available on request: 64ms (typ) and 128ms (typ)
■ Internal 5kΩ pull-up resistor
■ Operating Temperature -40°C to +105°C
■ Monitors external pushbutton override
■ Internal switch debounce circuitry
■ SOT23-3 package
Typical Operating Circuit
V_CC
GND
Connection Diagram
3
FM1233A
1
2
RESET
Controller
GND 1
FM1233A 3 V_CC
RESET 2
SOT23-3 Package
©2004 Fairchild Semiconductor Corporation
1
FM1233A Rev. E
www.fairchildsemi.com