January 2006

1

MIC1232

MIC2755

Micrel, Inc.

MIC1232

µP Supervisory Circuit

General Description

The MIC1232 is a multifunction circuit which monitors mi-

croprocessor activity, external reset and power supplies in

microprocessor based systems. The circuit functions include

awatchdogtime,powersupplymonitor,microprocessorreset,

and manual pushbutton reset input.

The power supply line is monitored with a comparator and

an internal voltage reference. /RST is forced low when an

out-of-tolerance condition exists and remains asserted for

as low as 1.4V.

The Watchdog input (/ST) monitors µP activity and will as-

sert /RST if no µP activity has occurred with in the watchdog

timeout period. The watchdog timeout period is selectable

with nominal period of 150, 600, 1200 milliseconds.

Typical Application

VCC

RST

µP

RESET

VCC

MIC1232

VCC

PBRST

TOL GND

ST

I/O

TD

Features

• Power OK/Reset time delay, 250ms min.

• Watchdog timer, 150ms, 600ms, or 1.2s typical

• Precision supply voltage monitor, select between 5% or

10% of supply voltage

• Available in 8-pin surface mount (SO)

• Debounced External reset input

• Low supply current, <18µA typical

Applications

• Automotive systems

• Intelligent systems

• Critical microprocessor power monitoring

• Battery powered computers

• Controllers

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

Ordering Information

Part Number

Temperature Range

Package

Standard

Pb-Free

MIC1232N

MIC1232NY

–40ºC to +85ºC

8-Pin PDIP

MIC1232M

MIC1232MY

–40ºC to +85ºC

8-Pin SOIC