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, highly accurate devices with integrated temperature compensated crystal oscillator (TCXO), ultra low-power consuming devices that enable long battery life, extended temperature devices up to 125ºC and AEC-Q100 qualified for automotive applications, several small package versions, and a real-time clock for one-time password generation for smart card applications. This training module will focus on the highly accurate RTC offerings. The PCF2127A and PCF2129A have both SPI and I²C interfaces with typical current consumption of 500 nA at 2 V supply and accuracy as good as ±3 ppm.