Real Time Clock (RTC) IC Clock/Calendar I²C, 2-Wire Serial 16-SOIC (0.154", 3.90mm Width)
Description The M41ST85W is a combination Serial Real-Time Clock, Microprocessor Supervisor, and NVRAM Supervisor. It is built in a low power CMOS SRAM process and has a 64-byte memory space with 44 bytes of NVRAM and 20 memory-mapped RTC registers (see Table 2 on page 20). The RTC registers are configured in binary coded decimal (BCD) format. Features ■ Automatic battery switchover and WRITE protect for: – Internal serial RTC and – External low power SRAM (LPSRAM) ■ 400kHz I2C serial interface ■ 3.0/3.3V operating voltage –VCC= 2.7 to 3.6V ■ Ultra-low battery supply current of 500nA (max) ■ RoHS compliant – Lead-free second level interconnect Serial RTC features ■ 400kHz I2C ■ 44 bytes of general purpose NVRAM ■ Counters for: – Seconds, minutes, hours, day, date, month, and year –Century – 10ths/100ths of seconds – Clock calibration register allows compensation for crystal variations over temperature ■ Programmable alarm with repeat modes – Functions in battery back-up mode ■ Power-down timestamp (HT Bit) ■ 2.5 to 5.5V oscillator operating voltage Microprocessor supervisor features ■ Programmable watchdog – 62.5ms to 128s time-out period ■ Early power-fail warning circuit (PFI/PFO) with 1.25V precision reference ■ Power-on reset/low voltage detect – Open drain reset output – Reset voltage, VPFD= 2.60V (nom) – Two reset input pins – Watchdog can be steered to reset output