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http://www.union-ic.com Rev.01 Jan.2015

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UM807/821/822

Detailed Description

RESET Timing

The reset signal is asserted LOW for the UM821 and HIGH for the UM822 when the power supply

voltage falls below the threshold trip voltage and remains asserted for at least 140ms after the power

supply voltage has risen above the threshold.

RESET

RESET

5V

0V

5V

0V

5V

0V

Pull MR

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for the reset pulse

MR

RESET

RESET

HIGH

LOW

0V

0V

Figure 2. RESET vs. MR

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Timing Diagram

Reset Output

A microprocessor’s (µP’s) reset input starts the µP in a known state. These μP supervisory circuits