Core component for the automotive sector and optical modules: Differential crystal oscillators

With the development of information technology, optical modules and differential crystals are one of the core components of fiber optic communication. Optical modules convert electrical signals from devices into optical signals, transmit them through optical fiber, and convert them into electrical signals again at the receiving end. Especially in the automotive field, with the continuous development of automotive intelligence and network connectivity, there is a growing demand for high-speed and stable data transmission.?

As a high-precision, low-jitter frequency source, differential crystals provide a reliable clock reference for key components such as in-vehicle communication systems, navigation systems, audio-visual systems, and radar systems.?This helps to ensure data synchronization and accuracy between the various systems, thereby improving the overall performance and safety of the vehicle.

1、Excellent immunity to interference.

2、Strong crosstalk and Electromagnetic Interference (EMI) suppression capabilities.

3、Low requirements for the integrity of reference levels (ground plane or power plane).

4、Minimal power consumption, high speed, and unaffected by temperature and voltage fluctuations.

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Working Principle of Differential Crystal Oscillators

Differential Crystal Oscillators can generate two differential signals with similar frequencies but opposite phases. These two signals can be combined or subtracted to generate a stable DC signal or a higher frequency signal. Their main function is to provide a stable reference clock, offering precise timing benchmarks for data conversion, transmission, and processing.

Different types of output signals and applicable scenarios for differential signals' voltage swing levels

Compared to Conventional Crystal Oscillators, Differential Crystal Oscillators have different output signal types, such as LVPECL, LVDS, and HCSL. Among these output signals, LVPECL and LVDS are widely used in various differential systems. So, what are the differences among these three output signals? And what are their differences in circuit operation principles?

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Low Voltage Positive Emitter-Coupled Logic (LVPECL)

Low Voltage Positive Emitter-Coupled Logic (LVPECL) is a common oscillator with a differential output format, with a voltage swing of approximately 800 mV and a differential crossing point of about 2V. LVPECL is widely used in fields that require low noise, such as graphics cards, PON, optical modules, and smart network cards. The diagram below shows a typical differential LVPECL waveform.

Low Voltage Differential Signaling (LVDS)

Low Voltage Differential Signaling (LVDS) is a common oscillator with a differential output format. Its power consumption is typically lower than other differential outputs, offering low power consumption and low electromagnetic radiation (EMI). The voltage swing is approximately 350 mV. LVDS is commonly used in applications such as audio/video processors, servers, routers, and switches. Below is a typical LVDS output waveform.

High-speed current steering logic (HCSL)

High-speed current steering logic (HCSL) is a common differential output format whose output is characterized by minimal jitter and low power consumption. This type of crystal is typically used in a wide range of scenarios that require high speed, low power consumption, and high performance, such as high-speed serial communications, clock distribution, and data paths within a system.?A typical HCSL output swing is 700 mV with a swing range of 0V to 700 mV, as shown in the figure below.

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CREC’S?Differential Crystal Oscillator Selection

In order to cope with the increasingly demanding high-speed data transmission and processing scenarios, Jingbao has launched a series of differential crystal oscillator products. These products feature low jitter, high accuracy, high frequency, miniaturization, and high temperature resistance, providing extremely reliable solutions for related applications.

1. Ultra-high frequency, ultra-low jitter: flexible customization, fast delivery

2.Small package: Preferred small size package crystal, save PCB space.

3.?Industrial grade:?industrial grade crystal temperature range to ensure stable operation.

4. Low power consumption:?low-power optical module saves energy and slows down heat generation.

5. Abundant output methods:?provide LVPECL, LVDS, HCSL, CML multiple output logic.

The differential crystal oscillator developed and produced by CREC supports multiple output signal types to ensure the efficient operation of optical modules. CREC is also committed to continuous innovation to provide customers with excellent performance and reliability to ensure the development of the optical module industry.