FM1233A 3-Pin 碌C Supervisor Circuit
September 2004
FM1233A
3-Pin 碌C 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 碌P. In the case of a switch, the closure will be
debounced by circuitry internal to the FM1233A.
Features
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Precision monitoring of 3.3V and lower voltage
microprocessor systems
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V
TH
values of 3.08V, 2.88V and 2.72V
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Automatic restart of microprocessor after power failure
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Reset Timeout Period Choice:
鈥?Options AC and AD: 140ms (min)/256ms (typ)
鈥?Option ABA: 17ms (min)/32ms (typ)
鈥?Available on request: 64ms (typ) and 128ms (typ)
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Internal 5k
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pull-up resistor
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Operating Temperature -40擄C to +105擄C
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Monitors external pushbutton override
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Internal switch debounce circuitry
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SOT23-3 package
Typical Operating Circuit
V
CC
3
FM1233A
Controller
1
GND
2
RESET
Connection Diagram
GND
1
FM1233A
3
V
CC
RESET
2
SOT23-3 Package
漏2004 Fairchild Semiconductor Corporation
1
www.fairchildsemi.com
FM1233A Rev. E
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