View ds1818 datasheet:

DS1818 3.3V EconoReset with Pushbutton www.dalsemi.com FEATURES PIN ASSIGNMENT Automatically restarts a microprocessor after 3 power failure Monitors pushbutton for external override Maintains reset for 150 ms after VCC returns to an in-tolerance condition Reduces need for discrete components 1 2 Precision temperature-compensated voltage SOT-23 PACKAGE reference and voltage sensor Accurate 5%, 10% or 20% power monitoring 1 2 3 Low-cost TO-92 or space saving surface mount SOT-23 packages available 1 2 3 Efficient open-drain output with internal 5.5 k?=pull-up resistor TO-92 PACKAGE See Mech. Operating temperature -40°C to +85°C Drawings Section PIN DESCRIPTION TO-92 1 RST Active Low Reset Output 2 VCC Power Supply 3 GND Ground SOT-23 1 RST Active Low