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Fairchild Semiconductor |
February 2003
FM1233B
3-Pin µC Supervisor Circuit
General Description
The FM1233B 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.
The device features a precision temperature-compensated volt-
age reference and comparator. When VCC falls to the threshold
voltage, a RESET pulse is issued, holding the output in the
active state. When power rises above VTH, the reset remains for
approximately 250 ms to allow the system clock and other cir-
cuits 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
s Precision monitoring of 5V and lower voltage microprocessor
systems
s VTH values of 4.62V, 4.38V and 4.12V
s Automatic restart of microprocessor after power failure
s 140ms (min) power-on RESET delay (typ.: 256ms)
s Internal 5kΩ pull-up resistor
s Other reset choices available: 32 to 128ms
s Operating Temperature -40°C to +105°C
s Monitors external pushbutton override
s Internal switch debounce circuitry
s SOT23-3 package
Typical Operating Circuit
VCC
GND
Connection Diagram
3
FM1233B
12
RESET
Controller
GND 1
FM1233B 3 VCC
RESET 2
SOT23-3 Package
©2002 Fairchild Semiconductor Corporation
FM1233B Rev. D
1
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Absolute Maximum Ratings
Votage on any pin relative to GND
VCC
RESET
Input Current
Output Current (RESET)
-0.3V to +6.0V
-0.3V to (VCC + 0.3V)
20mA
20mA
ESD Rating:
Human body model
Machine Model
Continuous Power Dissipation (TA = 70°C)
SOT23 (derate 4mW above 70°C)
Operating Temperature Range
>2kV
>200 V
300mW
-40°C to +105°C
Storage Temperature 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 (VCC = 5V; TA = -40°C to +105°C unless otherwise noted)
(Note 1)
Parameter
Operating Voltage
Supply Current
Reset Threshold
Reset Threshold
Reset Threshold
Reset Output Voltage
Reset Timeout Period
Pushbutton Detect
Pushbutton Release
Symbol
Conditions
VCC
ICC VCC < 5V
VTH FM1233BF
VTH FM1233BD
VTH FM1233BE
VOL FM1233B
tRST
PBVDET
PBVREL
FM1233B
FM1233B
FM1233B
Isink = 5mA
VCC = VTH(min)
VCC = 5V
Note 2
Min
1.2
4.40
4.16
3.91
140
0.8
Typ
3
4.62
4.38
4.12
256
0.3
Max
5.5
6
4.86
4.55
4.32
0.4
560
2.0
1.5
Units
V
µA
V
V
V
V
ms
V
V
Note 1: Testing at production is done at 25°C only. Limits over temperature are guaranteed by design.
Note 2: C = 100pF, VCC = 5V. It is recommended to connect 100pF capacitor between the Reset pin and Ground pin if pushbutton reset is implemented.
FM1233B Rev. D
2 www.fairchildsemi.com
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