在低功耗系統(tǒng)中啟用計時功能和延長電池壽命

　　電子跟蹤時間的能力使電子設備能夠?qū)崿F(xiàn)諸如維護日歷時間、定期喚醒系統(tǒng)啟動某些動作、以及時間戳測量數(shù)據(jù)等功能?，F(xiàn)在越來越多的系統(tǒng)實現(xiàn)時間保持功能。這些系統(tǒng)使用獨立的實時時鐘設備或帶有集成實時時鐘的處理器實現(xiàn)實時時鐘（RTC）功能。實時時鐘（RTC）允許系統(tǒng)跟蹤時間并將事件同步到用戶容易理解的時間基準。

　　在預計使用的手持式、便攜式和電池供電的設備，給予的方式提高了最終產(chǎn)品的數(shù)量。例如，電池供電設備的使用在調(diào)度系統(tǒng)事件和任務，并能使處理器在深度睡眠模式，大部分的時間，顯著降低了系統(tǒng)的功耗，延長電池壽命。此外，小型輕量電池模塊的晶片尺寸的低功耗RTC集成模塊中直接由電池供電的保證系統(tǒng)的計時信息不會丟失即使剩下的系統(tǒng)關機。

　　計時有時是在系統(tǒng)微控制器中使用內(nèi)置振蕩器完成的。然而，在某些情況下，需要一個外部獨立RTC。使用一個獨立的RTC具有低功耗的好處，更高的計時精度，并提高對系統(tǒng)鎖定的可靠性。

　　In most systems， the on-time is magnitudes less than the off-time. Therefore， power saving during the off-time is essential. In these systems， to save power， the user will generally shut down all circuitry that is not being used. However， it is still vital that the system maintains its time-keeping function. With the use of a standalone RTC during power-down modes， the power consumption could be as low as 100 nA， compared to the current consumption of a microcontroller with integrated RTC which could be up to 2 μA to 10 μA. By transferring the timekeeping function to the ultra-low power RTC， the microcontroller can go into hibernation mode and the system would only consume 100 nA to keep the RTC running. The system wake-up procedure can be programmed optimally to suit the application.