M41ST85W is a 3.0/3.3 V I2C combination serial RTC, NVRAM supervisor and microprocessor supervisor. It features automatic battery switchover and WRITE protection for internal serial RTC and external low power SRAM (LPSRAM). It also features 400 kHz I2C serial interface, 3.0/3.3 V operating voltage VCC=2.7 to 3.6 V, ultralow battery supply current of 500 nA (max), RoHS compliant, lead-free second level interconnect and so on.