Chipsun Knowledge｜Common Crystal Oscillators Used in Communication Electronic Equipment
Communication equipment has extremely high requirements for frequency stability and accuracy. Common types of crystal oscillators include general crystal oscillators, temperature-compensated crystal oscillators (TCXO), oven-controlled crystal oscillators (OCXO), and voltage-controlled crystal oscillators (VCXO). Among them, TCXO and OCXO are the most widely used, as they effectively compensate for temperature variations and ensure stable signal transmission.
For example:
TCXO is commonly used in mobile phones, base stations, and GPS devices.
OCXO is used in applications requiring ultra-high precision, such as satellite communication and precision measuring instruments.
In addition, 26 MHz crystal oscillators are frequently used in mobile phones and wireless communication modules, as they facilitate frequency multiplication to generate the required frequencies.
The pins of a quartz crystal oscillator refer to the soldering points connecting the component to the circuit, also known as “leads” or “pads”. They are generally divided into passive crystal oscillators and active crystal oscillators, which differ in pin count and functions.
When selecting a crystal oscillator for communication equipment, the key factors are frequency stability and accuracy, which are critical for reliable signal transmission.Please note the following key points:
1.Core Selection Criteria
(1)Frequency and AccuracyDetermined by the equipment type:
Consumer electronics (e.g., mobile phones): typically ±20 ppm
Industrial control: ±5 ppm
High-end communications such as 5G base stations: ±0.05 ppm to ±1 ppm
(2)Type Selection
Temperature-Compensated Crystal Oscillator (TCXO)Compensates for temperature changes; mainstream for communication equipment, wide operating temperature range (e.g., -40℃~85℃), high accuracy.
Oven-Controlled Crystal Oscillator (OCXO)Highest precision; used in satellite communication, precision measurement, and other ultra-high stability applications.
Voltage-Controlled Crystal Oscillator (VCXO)Allows fine frequency adjustment via voltage; used in phase-locked loops (PLL) or frequency calibration.
(3)Operating Temperature and StabilityEnsure the crystal oscillator’s temperature range covers the equipment environment:Industrial grade: -40℃~85℃,Automotive grade: -40℃~125℃
(4)Load Capacitance must match the circuit, otherwise oscillation will fail. Typically use NPO (C0G) capacitors of 10–30 pF.
(5)Package and SizeSelected based on PCB space. SMD packages are suitable for automated production and miniaturized designs save space.
2.Selection Guide by Communication Equipment Category
(1)Consumer Electronics (mobile phones, Bluetooth headsets)Prioritize SMD package, low power consumption, frequency accuracy ±20 ppm, operating voltage 1.8 V or 3.3 V.
(2)Industrial Control (PLC, sensors)Industrial-grade crystal oscillators, operating temperature -40℃~85℃, accuracy ±5 ppm, strong anti-interference capability.
(3)Communication Equipment (routers, 5G base stations)Extremely high accuracy and stability requirements; use OCXO or TCXO with precision within ±1 ppm.
(4)Optical Fiber CommunicationSelected according to transmission rate:1G/10G Ethernet: ±20 ppm to ±100 ppm,100G/400G coherent optical communication: ±1 ppm to ±5 ppm
3.Precautions
(1)Active vs. Passive Crystal Oscillators
Passive: low cost, used in low-accuracy applications
Active: stable output, used in high-speed communications (e.g., FPGA, 5G modules)
(2)Output WaveformMatched to the load:CMOS for logic level applications,differential square wave (LVPECL/LVDS) for high-frequency applications
(3)Aging and LifetimeConsider long-term stability; choose crystal oscillators with low aging rate to ensure long-term reliability.
In summary, crystal oscillator selection must comprehensively consider frequency, accuracy, type, environmental adaptability, and cost.