View rt9818-series datasheet:

RT9818 Micro-Power Voltage Detectors General Description Features Internally Fixed Threshold 1.2V to 5V in 0.1V Step The RT9818 is a micro-power voltage detector High Accuracy ± ± ±1.5% ± ± supervising the power supply voltage level for Low Supply Current 3µ µ µA µ µ microprocessors (µP) or digital systems. It provides No External Components Required internally fixed threshold levels with 0.1V per step ranging Quick Reset within 20µ µ µs µ µ from 1.2V to 5V, which covers most digital applications. It Built-in Recovery Delay Include 0ms, 55ms, 220ms, features low supply current of 3µA. The RT9818 performs 450ms Options supervisory function by sending out a reset signal Low Functional Sup