NXP’s RTC portfolio includes several devices to address different application needs. The devices include a low-cost 32 kHz time-base without time keeping registers, low-power consuming devices that enable long battery life, devices with extended temperature ranges up to 125 ºC and AEC-Q100 qualified for automotive applications, several small package versions and a real-time clock for a one-time password generation for smart card applications. Highlighted in blue are the low power RTC devices. The PCF2123 and PCF8523 are two of the lowest power consumption RTCs in the world. The PCF2123 has an SPI interface and the PCF8523 has an I²C interface.