关于RTC振荡电路与时钟精准度，晶诺威科技解释如下：
RTC振荡电路与时钟精准度
英文：RTC oscillator circuit and clock accuracy
Oscillator Circuit 振荡器电路
Usually the RTC uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate.
（RTC振荡电路范例：阴影区不要布信号线）
The Figure above shows a functional schematic of the oscillator circuit. If using a crystal with the specified characteristics, the startup time is usually less than one second.
通常RTC振荡电路使用外部32.768kHz晶体。振荡器电路不需要任何外部电阻或电容器即可运行。上图显示了振荡器电路的功能原理图。如果使用具有指定特性的晶体，则启动时间通常不到一秒钟。
The Table below specifies several key crystal parameters for the external crystal.
下图中列出了外部晶体的几个关键电气参数。
（外部晶体32.768KHz电气参数范例）
Clock Accuracy 时钟精度
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was trimmed. In order to improve the accuracy of high running, a set of 0pF-22pF negative load compensation capacitors should be placed outside the crystal end. The specific capacity is determined by the application layout and crystal vibration. Additional will be added by crystal frequency drift caused by temperature shifts. External circuit noise coupled into the oscillator circuit may result in the clock running fast. Figure above shows a typical PC board layout for isolating the crystal and oscillator from noise.
时钟的精度取决于晶体的精度以及振荡器电路的电容负载与修整晶体的电容载荷匹配的精度。为了提高RTC运行精度，晶体端外应放置一组0pF-22pF负载补偿电容器。具体容量由应用布局和晶体振动决定。温度变化引起的晶体频率漂移会增加额外量。耦合到振荡器电路的外部电路噪声可能导致时钟运行速度快。上图（RTC振荡电路范例）显示了一个典型的PCB电路板布局隔离晶体和振荡器的噪音。
NOTE: Connections for Standard 32.768kHz Quartz Crystal.
关于外接32.768KHz晶振
This internal oscillator is designed for operation with a crystal having a specified load capacitance of 6pF. This RTC can also be driven by an external 32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is floated.
请连接常规32.768kHz无源晶振（石英晶体谐振器）。
在上述范例中，该RTC内部振荡器需要与负载电容（CL）为6pF的32.768KHz无源晶振匹配使用。
该RTC方案也可以由外部32.768kHz振荡器（即：有源晶振32.768KHz）驱动。在这种配置中，X1引脚（X_IN信号输入脚）连接到外部振荡器信号，X2引脚（X_OUT信号输出脚）悬空。
