LM809/LM810

3-Pin Microprocessor Reset Circuits

General Description

The LM809/810 microprocessor supervisory circuits can be

used to monitor the power supplies in microprocessor and

digital systems. They provide a reset to the microprocessor

during power-up, power-down and brown-out conditions.

The function of the LM809/810 is to monitor the V

voltage, and assert a reset signal whenever this voltage

declines below the factory-programmed reset threshold. The

reset signal remains asserted for 240ms after V

above the threshold. The LM809 has an active-low RESET

output, while the LM810 has an active-high RESET output.

Seven standard reset voltage options are available, suitable

for monitoring 5V, 3.3V, and 3V supply voltages.

With a low supply current of only 15µA, the LM809/810 are

ideal for use in portable equipment. The LM809/LM810 are

available in the 3-pin SOT23 package and in the 6-Lead LLP

package.

Features

n

Precise monitoring of 3V, 3.3V, and 5V supply voltages

n

Superior upgrade to MAX809/810

n

Fully specified over temperature

n

140ms min. Power-On Reset pulse width, 240ms typical

Active-low RESET Output (LM809)

Active-high RESET Output (LM810)

n

Guaranteed RESET Output valid for V

CC

≥1V

n

Low Supply Current, 15µA typ.

n

Power supply transient immunity

Applications

n

Microprocessor Systems

n

Computers

n

Controllers

n

Intelligent Instruments

n

Portable/Battery-Powered Equipment

n

Automotive

Typical Application Circuit

10105701

Connection Diagrams

10105702

( ) are for LM810

10105715

Top View

See NS package Number LDB06A

( ) are for LM810

September 2002

© 2002 National Semiconductor Corporation

DS101057

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