UM805 Datasheet, PDF (11/14 Pages) Union Semiconductor, Inc. – Voltage Monitors with Manual Reset Input

UM805/811/812
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UM805 Open-Drain RESET Output Allows Use with Multiple Supplies
Generally, the pull-up connected to the UM805 will connect to the supply voltage that is being
monitored at the IC’s V_CC pin. However, some systems may use the open-drain output to level-shift
from the monitored supply to reset circuitry powered by some other supply (Figure 6). Note that as
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the UM805’s V_CC decreases below 1V, so does the IC’s ability to sink current at RESET. Also,
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with any pull-up, RESET will be pulled high as V_CC decays toward 0. The voltage where this
occurs depends on the pull-up resistor value and the voltage to which it is connected.
5.0V
3.3V
V_CC
UM805
RESET
GND
Rpull-up
V_CC
5V System
RESET
GND
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Figure 6. UM805 Open-Drain RESET Output Allows Use with Multiple Supplies
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http://www.union-ic.com Rev.01 Jan.2015
11/14