在低功耗系統(tǒng)中啟用計(jì)時(shí)功能和延長(zhǎng)電池壽命

　　電子跟蹤時(shí)間的能力使電子設(shè)備能夠?qū)崿F(xiàn)諸如維護(hù)日歷時(shí)間、定期喚醒系統(tǒng)啟動(dòng)某些動(dòng)作、以及時(shí)間戳測(cè)量數(shù)據(jù)等功能。現(xiàn)在越來越多的系統(tǒng)實(shí)現(xiàn)時(shí)間保持功能。這些系統(tǒng)使用獨(dú)立的實(shí)時(shí)時(shí)鐘設(shè)備或帶有集成實(shí)時(shí)時(shí)鐘的處理器實(shí)現(xiàn)實(shí)時(shí)時(shí)鐘（RTC）功能。實(shí)時(shí)時(shí)鐘（RTC）允許系統(tǒng)跟蹤時(shí)間并將事件同步到用戶容易理解的時(shí)間基準(zhǔn)。

　　在預(yù)計(jì)使用的手持式、便攜式和電池供電的設(shè)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(shè)備的使用在調(diào)度系統(tǒng)事件和任務(wù)，并能使處理器在深度睡眠模式，大部分的時(shí)間，顯著降低了系統(tǒng)的功耗，延長(zhǎng)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(jì)時(shí)信息不會(huì)丟失即使剩下的系統(tǒng)關(guān)機(jī)。

　　計(jì)時(shí)有時(shí)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(gè)外部獨(dú)立RTC。使用一個(gè)獨(dú)立的RTC具有低功耗的好處，更高的計(jì)時(shí)精度，并提高對(duì)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.