The M48T18-150PC is a low-power and low-voltage Serial Peripheral Interface (SPI) Timekeeper RAM from STMicroelectronics. It is an 8K x 8 Static RAM (SRAM) device with Voltage-Controlled Oscillator (VCO) that operates from 1.8/2.75V to 5.5V. The device features a Real-Time Clock (RTC) with calendar, alarm, and periodic interrupt functions. Its “power-fail detect-and-switch” capability permits system designers to observe a cohesive RTC function during power cycling through an integrated switching circuit. Additionally, it has a battery-backup functionality that keeps all contents of RAM and RTC registers intact even when the device is not powered. The device includes two watchdog timers with their own operating power sources and independent enable functions. The device is available in 28-pin SOP, plastic DIP, SOJ, and TSSOP packages.