FM1233ACS3X View Datasheet(PDF) - Fairchild Semiconductor

Part Name

Description

Manufacturer

FM1233ACS3X

3-Pin µC Supervisor Circuit

Fairchild Semiconductor 

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 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

asserted for a minimum period (tRST) 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

■ VTH 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

VCC

GND

Connection Diagram

3

FM1233A

1

2

RESET

Controller

GND 1

FM1233A 3 VCC

RESET 2

SOT23-3 Package

©2004 Fairchild Semiconductor Corporation

1

FM1233A Rev. E

www.fairchildsemi.com

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