SiTime Sharpens Precision Timing With Two Mission

In digital electronics, the most important design consideration is timing: without clean clock signals and properly-designed sequential logic, nothing will work. When we extrapolate this to mission-critical applications like aerospace and defense, timing becomes even more crucial.

This week, SiTime released two new oscillator families built for precision timing in aerospace and defense.

In this article, we’ll discuss the importance of precision timing in these applications and some unique features of SiTime's new Endura oscillator families.

In military and aerospace applications, devices are expected to work in real time with little to no margin for error.

In aerospace applications, precision timing is crucial for navigation, guidance, and control systems. For example, GPS systems may rely on precise timing to accurately determine the location of a vehicle. Here, any errors in timing could cause the GPS system to produce incorrect coordinates, which can lead to navigation errors and even collisions. Similarly, in military applications, precision timing is essential for guidance, communication, and radar systems. These systems rely on accurate timing to function properly and provide critical information to the operators.

Unfortunately, while these use cases need precision timing the most, they are often applications where it is hardest to achieve. The main reason for this is that aerospace and defense applications tend to be deployed in extremely harsh environmental conditions in the presence of extreme temperatures, high vibration, and electromagnetic interference (EMI). These conditions can cause traditional oscillators to produce jitter and drift, leading to system malfunctions and even mission failure.

To overcome the impact of harsh environmental conditions, two oscillator designs have become very popular. The first design is the temperature-compensated crystal oscillator (TCXO).

On a high level, TCXOs operate using a temperature compensation network and a pulling network.

In this architecture, a compensation network senses the ambient temperature, which impacts the oscillator’s output, and drives the pulling network accordingly to adjust the oscillator's frequency. The aim of the compensation network is to produce a voltage that is the complement (180-degree out of phase) of the crystal’s temperature response to effectively cancel out the impacts of temperature. With TCXOs, devices can achieve anywhere from 10x to 40x better temperature stability than a standard VCXO.

The other design is a differential oscillator. Like standard differential signaling, a differential oscillator produces two outputs, a clock signal and its complement (180-degree phase-shifted version). If the two differential signals are routed identically and spatially close to one another, any environmental noise will impact both signals equally. At the receiver, the two signals are subtracted from one another, effectively canceling out any common-mode noise encountered along the PCB trace. In this way, differential oscillators offer high stability and accuracy for precision timing.

This week, SiTime released two new families of precision timing oscillators for aerospace and defense applications.

The first family is the Endura SiT5541 family, which is a ruggedized TCXO-based oscillator. The device offers output frequencies anywhere from 1–60 MHz while offering a ±10-ppb stability over a temperature range from -40°C to 105°C. The device also offers resistance to vibration, airflow, and EMI. Additionally, the device comes in a 7 mm x 5 mm package and offers power consumption as low as 110 mW.

The other SiTime family released this week was the Endura SiT9551/SiT9356/SiT9357 ultra-low-jitter differential oscillators. These differential oscillators cover various frequency ranges, with offerings meeting the needs from 1 MHz to 920 MHz. Additionally, the products in this family feature 9 fs/mV power supply noise rejection (PSNR), 0.04 ppb/g g-sensitivity, and ±20 to ±50 ppm frequency stability over a full temperature range from -55°C to 125°C.