View rt9808-series datasheet:

Preliminary RT9808 Micro-Power Voltage Detectors General Description Features The RT9808 is a micro-power voltage detector Internally Fixed Threshold 1.5V to 5V in 0.1V Step supervising the power supply voltage level for ±2% Accuracy ± ± ± microprocessors (µP) or digital systems. It provides Low Supply Current 3µ µA µ µ internally fixed threshold levels with 0.1V per step Quick Reset within 20µ µS µ µ ranging from 1.5V to 5V, which covers most digital Built-in Recovery Delay 200mS applications. It features low supply current of 3µA. Low Functional Supply Voltage 0.9V N-Channel Open Drain Output The RT9808 performs supervisory function by Small 3-Pin SOT-23/SOT89 and 5-Pin SOT-25 sending out a reset signal whenever the VDD voltage Packa