μP Reset Circuits with Long Manual Reset Setup Period
UM807/821/822 SOT143
General Description
The UM807/821/822 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 UM807/821/822 also provide a debounced manual reset input with long setup period.
On all devices, the reset output asserts when the VCC supply voltage drops below its specified
threshold. The reset output remains asserted for the reset timeout period (240ms typ) after VCC rises
above the reset threshold. The reset output is one-shot pulse asserted for the reset timeout period
(140ms min) when manual reset input is held low for a fixed setup timeout period. These devices
ignore manual reset transitions of less than the fixed setup timeout period.
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The UM807 has an active-low RESET with open-drain output, the UM821 has an active-low
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RESET with push-pull output, and the UM822 has an active-high RESET with push-pull output.
These devices, offered in small SOT143 package, are fully guaranteed over the extended
temperature range (-40°C to +85°C).
Applications
Features
Set-Top Boxes
Consumer Electronics
DVD Players
Cable/DSL Modems
MP3 Players
Industrial Equipments
Automotive
No External Components
VCC Transient Immunity
Correct Logic Output Guaranteed to VCC=1.0V
Precision VCC Monitoring of 3.0V, 3.3V and 5.0V
Supplies
2μA Supply Current
140ms Minimum Power-On Reset Pulse Width
Available in 3 Manual Reset Setup Periods (tMR):
Medical Devices
A: 10.08s
B: 6.72s
C: 1.68s
Available in 3 Output Configurations:
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Open-Drain Active-Low RESET Output(UM807);
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Push-Pull Active-Low RESET Output(UM821)
Push-Pull Active-High RESET Output(UM822)
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 1/17