Fairchild Semiconductor FM1233BE Datasheet
©2002 Fairchild Semiconductor Corporation
1
www.fairchildsemi.com
February 2003
FM1233B 3-Pin µC Supervisor Circuit
FM1233B Rev. D
FM1233B
3-Pin µC Supervisor Circuit
General Description
The FM1233B is a supervisor circuit that monitors a microprocessor 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.
The device features a precision temperature-compensated voltage 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 circuits to stabilize. The reset output of FM1233B is of open-drain
active low type.
The FM1233B 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 FM1233B.
Features
■
Precision monitoring of 5V and lower voltage microprocessor
systems
■
V
TH
values of 4.62V, 4.38V and 4.12V
■
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
■
Monitors external pushbutton override
■
Internal switch debounce circuitry
■
SOT23-3 package
Typical Operating Circuit
Connection Diagram
SOT23-3 Package
1
FM1233B
Controller
2
3
VCC
GND
RESET
GND
VCC
RESET
1
FM1233B
2
3
FM1233B 3-Pin µC Supervisor Circuit
2
www.fairchildsemi.com
FM1233B Rev. D
Absolute Maximum Ratings
Votage on any pin relative to GND
V
CC
-0.3V to +6.0V
RESET
-0.3V to (V
CC
+ 0.3V)
Input Current 20mA
Output Current (RESET
) 20mA
ESD Rating:
Human body model >2kV
Machine Model >200 V
Continuous Power Dissipation (T
A
= 70°C)
SOT23 (derate 4mW above 70°C) 300mW
Operating T emper ature Range -40°C to +105°C
Storage T emper ature Range -65°C to +150°C
Lead Temperature (soldering, 10s) +300°C
These are stress ratings only, and functional operation is not implied for these levels or beyond. Exposure to Absolute Maximum
Rating conditions for extended periods may affect device reliability.
Electrical Characteristics (V
CC
= 5V; T
A
= -40°C to +105°C unless otherwise noted)
(Note 1)
Note 1 : Testing at production is done at 25°C only. Limits over temperature are guaranteed by design.
Note 2 : C = 100pF, V
CC
= 5V. It is recommended to connect 100pF capacitor between the Reset pin and Ground pin if pushbutton reset is implemented.
Parameter Symbol Conditions Min Typ Max Units
Operating V oltage V
CC
1.2 5.5 V
Supply Current I
CC
V
CC
< 5V 3 6 µA
Reset Threshold V
TH
FM1233BF 4.40 4.62 4.86 V
Reset Threshold V
TH
FM1233BD 4.16 4.38 4.55 V
Reset Threshold V
TH
FM1233BE 3.91 4.12 4.32 V
Reset Output Voltage V
OL
FM1233B I
sink
= 5mA
V
CC
= V
TH
(min)
0.4 V
Reset Timeout Period t
RST
FM1233B 140 256 560 ms
Pushbutton Detect PBV
DET
FM1233B V
CC
= 5V 0.8 2.0 V
Pushbutton Release PBV
REL
FM1233B Note 2 0.3 1.5 V
Loading...