One article takes you to understand: Why is the real-time clock (RTC) crystal oscillator frequency 32.768KHz?

In various electronic devices, Real Time Clock (RTC) is a crucial component used to provide accurate time and date information. Whether it's watches, computers, smartphones, smart homes, or wearable devices, RTC is almost ubiquitous. One of the core components of RTC is the crystal oscillator, whose frequency is usually fixed at 32.768KHz. The selection of this frequency is not accidental, but has precise mathematical basis. This article will analyze in detail the reasons behind this frequency selection from multiple perspectives.

1、 Binary frequency division advantage

32.768KHz is a special frequency because it has a natural affinity with binary systems. 32.768KHz is equal to 2 ^ 15 Hz, which means that the crystal oscillator oscillates 32768 times per second. For a system that requires timing in seconds, this frequency is very convenient. Only a 15 level binary divider is needed to accurately divide the 32.768KHz signal into 1Hz (1Hz is calculated by periodically changing once per second, so 1 second is equal to 1Hz), that is, one pulse per second. Then, by counting this second pulse signal and the initial time we set, we can know the current time and date. This frequency division method is extremely simple and efficient, suitable for the design and implementation of digital circuits, and reduces the need for complex frequency division circuits.

2、 Low power consumption advantage

RTC usually needs to remain operational even when the device is turned off or in standby mode to record time. Therefore, power consumption is a crucial consideration. The 32.768KHz crystal oscillator has very low energy consumption and is very suitable for devices that rely on battery power, such as watches, calculators, sensors, and portable electronic products. The low power consumption feature not only extends the battery life of the device, but also ensures its reliable operation over a long period of time.

3、 Small size and low cost advantages

The 32.768KHz crystal oscillator has become a standard component in the market, with a mature production process and effective control of manufacturing costs. The cost advantage brought by this scale effect makes it widely used in various electronic products. In addition, the 32.768KHz crystal oscillator has a small volume and is easy to integrate into various miniaturized electronic devices. This makes it particularly popular in designs with limited space, thus supporting more compact and lightweight device designs.

4、 Advantages of high stability and accuracy

Although 32.768KHz is not the most accurate frequency, its stability and accuracy are sufficient to meet most application requirements. This frequency crystal oscillator can maintain high stability under different temperature and environmental conditions, ensuring the reliability of time measurement. This is very important for devices that require long-term operation and accurate time recording.

5、 Industry standardization

The 32.768KHz crystal oscillator has become the industry standard in RTC applications. The advantages brought by standardization are obvious, as it ensures that the components produced by various manufacturers have good compatibility and interchangeability. For designers and engineers, using this standard frequency crystal oscillator can simplify the design process and provide high supply chain stability.

The 32.768KHz crystal oscillator is used as the standard frequency for real-time clock (RTC) crystal oscillators. The choice is the result of a combination of multiple factors. The convenience, low power consumption, cost and size considerations, stability and accuracy guarantees of binary frequency division have made it widely used in various electronic devices. Industry standardization further consolidates its position in RTC applications. The widespread application of 32.768KHz crystal oscillators not only promotes the development of electronic products, but also brings consumers a more reliable and durable user experience.