Why is the crystal oscillator required to be next to the IC?

　　The crystal oscillator generates mechanical vibrations of a fixed frequency through electrical excitation, and the vibrations will generate current feedback to the circuit. After receiving the feedback, the circuit amplifies the signal and uses the amplified electrical signal to excite the mechanical vibration of the crystal oscillator again. The crystal oscillator then feeds back the current generated by the vibration to the circuit, and so on. When the excitation electrical signal in the circuit is the same as the nominal frequency of the crystal oscillator, the circuit can output a strong signal and a stable frequency sine wave. The shaping circuit then converts the sine wave into a square wave and sends it to the digital circuit for use. The problem is that the output capacity of the crystal oscillator is limited. It only outputs electrical energy in milliwatts. Inside the IC ( integrated circuit ), this signal is amplified hundreds or even thousands of times by an amplifier before it can be used normally. The crystal oscillator and the IC are generally connected by a copper trace. This trace can be regarded as a section of wire or several sections of wire. When the wire cuts the magnetic lines of force, it will generate current. The longer the wire, the stronger the current generated. In reality, magnetic lines of force are not common, but electromagnetic waves are everywhere, such as: wireless broadcast transmission, TV tower transmission, mobile phone communication, etc. The connection between the crystal oscillator and the IC becomes a receiving antenna. The longer it is, the stronger the received signal will be, and the stronger the electrical energy will be. When the received electrical signal strength exceeds or approaches the signal strength generated by the crystal oscillator, the amplifier circuit in the IC will no longer output a square wave of a fixed frequency, but a messy signal, causing the digital circuit to fail to work synchronously and make mistakes. Therefore, when drawing a PCB (circuit board), the closer the crystal oscillator is to its amplifier circuit (IC pin), the better.