4-Pin μP Voltage Monitors with Manual Reset Input
UM805/811/812 SOT143
General Description
The UM805/811/812 are low-power microprocessor (μP) supervisory circuits used to monitor power
supplies in μP and digital systems. They provide excellent circuit reliability and low cost by
eliminating external components and adjustments when used with 5V-powered or 3V-powered
circuits. The UM805/811/812 also provide a debounced manual reset input.
These devices perform a single function: They assert a reset signal whenever the VCC supply voltage
falls below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the
reset threshold. Reset thresholds are available for operation with a variety of supply voltages.
The UM805 has an open-drain output stage, while the UM811/812 have push-pull outputs. The
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UM805’s open-drain RESET output requires a pull-up resistor that can be connected to a voltage
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higher than VCC. The UM805/811 have an active-low RESET output, while the UM812 has an
active-high RESET output. The reset comparator is designed to ignore fast transients on VCC, and
the outputs are guaranteed to be in the correct logic state for VCC down to 1V.
Low supply current makes the UM805/811/812 ideal for use in portable equipments. The devices
come in a 4-pin SOT143 package.
Applications
Features
Computers
Controllers
No External Components
VCC Transient Immunity
Portable/Battery-Powered Equipments Correct Logic Output Guaranteed to VCC=1.0V
Intelligent Instruments
Critical μP and μC Power Monitoring
Precision VCC Monitoring of 3.0V, 3.3V and 5.0V
Supplies
2μA Supply Current
140ms Minimum Power-On Reset Pulse Width
Guaranteed Over Temperature
Available in 3 Output Configurations:
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Open-Drain Active-Low RESET Output(UM805)
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Push-Pull Active-Low RESET Output(UM811)
Push-Pull Active-High RESET Output(UM812)
4-Pin SOT143 Package
Wide Operation Temperature: -40°C to +85°C
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http://www.union-ic.com Rev.01 Jan.2015 1/14