BUY DS1321S https://www.utsource.net/itm/p/5966698.html
Nonvolatile Controller
Description: The DS1321S is a low-power, real-time clock (RTC) with a built-in power-on reset circuit. Features: - Low power consumption: Active current of 500nA, standby current of 1.5uA - Operating voltage range: 2.2V to 5.5V - Built-in power-on reset circuit - Programmable clock/calendar - 24-hour or 12-hour time format - Automatic leap year correction - Programmable alarm - Programmable square wave output - Battery backup Applications: - Automotive - Industrial - Medical - Consumer electronics - Wearable devices - Home appliances - Security systems (For reference only)