The PCF2127A and PCF2129A are low-power RTCs with integrated TCXOs and accuracy as good as ±3 ppm. The devices require no external crystal, tuning capacitor, or temperature sensor. They come calibrated from the factory and ready to use at first power up with no requirement for re-calibration due to aging. The PCF2127A includes 512 Bytes of RAM which may be used for retaining critical data during power down, while the PCF2129A does not include any RAM. These devices consume as low as 500 nA, typically, with a 2 V power supply.