Fairchild Semiconductor FM1233AD Datasheet

©2003 Fairchild Semiconductor Corporation

1

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February 2003

FM1233A 3-Pin µC Supervisor Circuit

FM1233A Rev. D

FM1233A
3-Pin µC Supervisor Circuit

General Description

The FM1233A 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 3V 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 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 2.88V, 2.72V

■

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

FM1233A

Controller

2

3

V

CC

GND

RESET

GND

V

CC

RESET

1

FM1233A

2

3

FM1233A 3-Pin µC Supervisor Circuit

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FM1233A Rev. D

Absolute Maximum Ratings

Voltage 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

Continuous Power Dissipation (T

A

= 70°C)

SOT23 (derate 4mW above 70°C) 300mW
Operating Temperature Range -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 (V

CC

= 3.3V; 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

= 3.3V. 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 3.3 5.5 V

Supply Current I

CC

V

CC

< 3.3V 3 6 µA

Reset Threshold V

TH

FM1233AC 2.70 2.88 2.97 V

Reset Threshold V

TH

FM1233AD 2.58 2.72 2.86 V

Reset Output Voltage V

OL

FM1233A I

SINK

= 5mA

V

CC

= V

TH

(min)

0.4 V

Reset Timeout Period t

RST

FM1233A 140 256 560 ms

Pushbutton Detect PBV

DET

FM1233A V

CC

= 3.3V 0.8 2.0 V

Pushbutton Release PBV

REL

FM1233A Note 2 0.3 1.5 V

FM1233A 3-Pin µC Supervisor Circuit

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FM1233A Rev. D

Typical Operating Characteristics

Supply Current Vs. Temperature

Power up Reset Timeout Vs. Temperature

0

2

4

6

8

10

0

2

4

6

8

10

+110C+25C-55C

Temperature (C)

I

CC

(µA)

VCC = 3.3V

100

200

300

400

500

600

100

200

300

400

500

600

+105C+25C-40C

Temperature (C)

Power up Reset timeout (ms)