On the miniature circuit board of a Bluetooth earphone, there is a tiny crystal oscillator. Although inconspicuous, it plays a decisive role in the performance of the earphone. From the perspective of Bluetooth technology principles, Bluetooth devices rely on the 2.4GHz band for short-range wireless communication. In this crowded frequency band, stable data transmission and smooth pairing connections depend on precise and stable clock signals, which is exactly the mission of the crystal oscillator. If the oscillator is not properly selected, the earphone may suffer from audio stuttering, unstable connections, or even failure to pair.
01
Frequency Tolerance
The frequency tolerance of crystal oscillators is generally between ±10ppm and ±30ppm. In applications like Bluetooth, which require extremely high frequency stability, it is recommended to prioritize oscillator products with a precision of ±10ppm or higher.
02
Load Capacitance Cannot Be Overlooked
For passive crystal oscillators, load capacitance is a key parameter. It is necessary to strictly select a crystal oscillator with a corresponding load capacitance value based on the load parameters required by the chip design. Common Bluetooth oscillator load capacitance values are 7pF, 9pF, and 12pF, with 9pF being the most widely used. In actual selection, the required oscillator load capacitance in the chip manual must be accurately matched to ensure the oscillator operates in its optimal state.
03
Package Size Should Fit Earphone Design
Bluetooth earphones aim to be compact and portable, requiring the oscillator to be small enough in size. Currently, the mainstream crystal oscillator packages for Bluetooth earphones include 1612, 2016, and 2520.
04
Temperature Requirements
The typical operating temperature range for crystal oscillators is -20℃ to +70℃. However, Bluetooth earphones are used in complex scenarios and may encounter extreme heat or cold. If the earphones need to operate stably across a wider temperature range, it is recommended to choose wide-temperature crystal oscillators with a range of -40℃ to +85℃.
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