LM809/LM810 3-Pin Microprocessor Reset Circuits
September 2002
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
CC
supply
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
CC
rises
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
Precise monitoring of 3V, 3.3V, and 5V supply voltages
Superior upgrade to MAX809/810
Fully specified over temperature
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
n
n
n
n
Applications
n
n
n
n
n
n
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Portable/Battery-Powered Equipment
Automotive
Typical Application Circuit
10105701
Connection Diagrams
10105702
( ) are for LM810
10105715
Top View
See NS package Number LDB06A
( ) are for LM810
© 2002 National Semiconductor Corporation
DS101057
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