1 Features

1• Precision Monitoring of Supply Voltages

– Available Threshold Options:

2.63 V, 2.93 V, 3.08 V, 4.38 V, 4.63 V

• Superior Upgrade to MAX809 and MAX810

• Fully Specified Over Temperature

• 140-ms Minimum Power-On Reset Pulse Width,

240-ms Typical

– Active-Low RESET Output (LM809)

– Active-High RESET Output (LM810)

• Ensured RESET Output Valid for VCC ≥ 1 V

• Low Supply Current, 15-μA Typical

• Power Supply Transient Immunity

2 Applications

• Factory Automation

• Building Automation

• Programmable Logic Control

• Renewable Energy

• Microprocessor Systems

• Computers

• Controllers

• Intelligent Instruments

• Portable/Battery-Powered Equipment

• Automotive

3 Description

The LM809 and LM810 microprocessors 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, powerdown

and brown-out conditions.

The function of the LM809 and LM810 are to monitor

the VCC supply voltage, and assert a reset signal

whenever this voltage declines below the factoryprogrammed

reset threshold. The reset signal

remains asserted for 240 ms after VCC 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 5-V, 3.3-V, and 3-V supply

voltages.

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

and LM810 are ideal for use in portable equipment.