Experts' Corner

Jitter is the timing variations of a set of signal edges from their ideal values and is typically caused by noise or other disturbances in the system. Learn about the different types of jitter and what causes it, plus best practices for measuring jitter using a real time oscilloscope in this application note.

This application provides a brief theoretical overview of phase noise and methods of phase noise measurement, and then focuses on practical phase noise measurement recommendations such as properly connecting a signal under test to the instrument, setting up the phase noise analyzer, and choosing appropriate settings.

PTP is a two-way time transfer protocol that is addressed in the IEEE 1588 standard, which defines the protocol for time and frequency synchronization in packet networks. This document focuses on standards within ITU-T SG15/Q13 and its application to IEEE 1588, and the requirements to telecom boundary clocks (T-BC) and telecom time slave clocks (T-TSC) in a network with full timing support.

Differential oscillators are used in high performance applications and offer higher robustness to power supply noise. This application note provides termination recommendations for SiTime differential oscillator families with LVPECL, LVDS, or HCSL output drivers. Interfaces for driving CML or HCSL clock inputs with LVPECL output are also discussed.

Every digital electronic device requires a reference clock and oscillators are widely used to serve that purpose. Verifying frequency characteristics of high-performance devices requires accurate frequency measurement. This document provides an overview of frequency measurement methods and instruments to help the users of SiTime MEMS oscillators take accurate frequency measurements.

One of the most common instruments used to measure jitter is the real-time digital oscilloscope (scope). Real-time oscilloscopes must be configured properly to make accurate jitter measurements. This application note provides general guidelines to setup an oscilloscope for best jitter measurement accuracy.

Every electronic system needs a timing device. And crystal (XTAL) resonators are often the go-to solution. However, oscillators, which pair a resonator with an oscillator IC into one complete integrated timing device, offer several benefits compared to XTALs. These benefits are further extended with MEMS timing technology.

In SyncE and PTP applications, local oscillators must deliver a stable reference regardless of environmental factors. This paper describes the performance requirements and characteristics of various TCXOs used in telecom systems and presents measurement results for ADEV, TDEV (wander), and MTIE under airflow and temp transients. This paper was presented at WSTS - the Workshop on Synchronization and Timing Systems.

For the first time, PCIe allows Refclk jitter compliance to be measured using a phase noise analyzer. Learn about the latest PCIe BASE Rev. 5.0 specs for determining Refclk jitter compliance, about the pros/cons of phase noise vs oscilloscope methods, how phase noise aliases in sampled systems, and algorithm development. This topic was presented at DesignCon. (Presentation Slides)

This paper describes a novel DualMEMS™ architecture, how it differs in construction and fabrication compared to quartz-based devices, and how thermal coupling affects oscillator performance in response to thermal disturbances (frequency slope). Thermal simulations showing temperature offsets are presented.

This paper presents a dual-MEMS resonator-based temperature sensor with 20-μK resolution and conversion rate of 200 S/s, and FOM of 0.04 pJK2. The implementation of a MEMS resonator design with two functional modes and associated circuitry are discussed. This paper appeared in the IEEE Journal of Solid-State Circuits.

Precision MEMS oscillators require a TDC that adjusts the multiplication factor of a frac-N PLL to compensate for frequency variation over temperature. This paper presents a TDC based on dual-MEMS resonators with 40 μK resolution and FOM of 0.12pJK2 that has little impact on phase noise. This paper was presented at ISSCC. (Presentation Slides)

This paper describes the system-level and circuit-level design of the first production 32-kHz low-power MEMS-based oscillator (±100 ppm) and TCXO (±3 ppm) with a small form-factor for timekeeping and low power functions in space-constrained mobile devices. This paper appeared in the IEEE Journal of Solid-State Circuits.

Today’s 32 kHz quartz resonators and oscillators are facing challenges in size reduction. This paper introduces a 32 kHz MEMS-based oscillator suited for mobile time-keeping applications that require small form-factor, tight frequency stability, and micro-power 32.768 kHz clock references. This paper was presented at ISSCC. (Presentation Slides)

This paper introduces the first commercial MEMS TCXO that delivers <1 ppm frequency stability from -40 to +85°C. Its system architecture, MEMS resonator, and key circuit blocks are described along with accompanying benefits, such as programmability and improved reliability and robustness. This paper was presented at AACD.

Programmable oscillators offer flexibility for clock tree optimization and spread-spectrum modulation for EMI reduction in FPGA-based applications. This paper introduces a timing architecture that helps designers improve system performance and solve clocking issues. This paper was presented at ESC. (Presentation Slides)

For low bandwidth PLLs, high-Q controlled oscillators offer low gain and high stability. This paper examines system flexibility and robustness along with the impact of quantization, update delay and loop performance for: 1) varactor-based VCXOs, 2) PLL-based VCXOs, and 3) digitally-controlled oscillators. This paper was presented at ESC. (Presentation Slides)