September 2005

1

MIC811/812

MIC811/812

Micrel

MIC811/812

Microprocessor Reset Circuits

General Description

The MIC811 and MIC812 are inexpensive microprocessor

supervisory circuits that monitor power supplies in micropro-

cessor based systems.

The function of this device is to assert a reset if either the

power supply drops below a designated reset threshold

level or /MR is forced low. Several different reset threshold

levels are available to accommodate 3V, 3.3V or 5V powered

systems.

The MIC811 has an active low /RESET output, while the

MIC812 offers an active high RESET output. The reset output

is guaranteed to remain asserted for a minimum of 140ms

Having a push-pull output stage, the MIC811/812 does not

require a pull-up resistor at the output. The MIC811/812

comes in a 4-pin SOT-143 package.

If a microprocessor voltage supervisor with an open-drain

output stage is needed, see MIC6315.

Features

• Precision voltage monitor for 3V, 3.3V or 5V power sup-

plies

• 5µA typical supply current

• 140ms minimum reset pulse width available

• Manual reset input

• Available in 4-pin SOT-143 package

Applications

• Portable equipment

• Intelligent instruments

• Critical microprocessor power monitoring

• Printers/computers

• Embedded 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

Typical Application

VCC

RESET

µP

RESET

VCC

MIC811

VCC

MR