Enabling 5G equipment to be deployed anywhere

Rajesh Vashist, CEO of SiTime, stated: “Timing is potentially the single biggest point of failure in 5G systems and can impact performance, reliability, and revenue. 5G timing is a complex challenge for system OEMs, and requires a new approach beyond traditional, component-level methods that are in use today. To solve this, SiTime pioneered a systems approach with Emerald to help our customers achieve their highest level of performance and capability. By combining our revolutionary MEMS with programmable analog, innovative packaging and high-performance algorithms, we have created a solution that is up to 20 times better than what is currently available.”

SiTime’s Emerald Platform is the first MEMS oven controlled oscillator (OCXO) in the industry. OCXOs offer the pinnacle of performance in timing and are critical to the reliable operation of all communications networks. However, quartz-based OCXOs are extremely sensitive to environmental stressors such as vibration, temperature changes and shock, which can degrade network performance, reduce uptime, and impact mission-critical services such as advanced driver assistance systems (ADAS). SiTime’s Emerald OCXOs can solve these problems.

Joe Madden, Principal Analyst at Mobile Experts, added: “As mobile operators move into 5G and edge computing, they will require much tighter time synchronisation in the radio equipment, which necessitates the use of OCXOs. Prior to 5G, this OCXO was deployed in a well-controlled environment. Now, the computing, core network, and radio will be collapsed into a system that may be deployed in an uncontrolled environment such as a tower, rooftop, or lamppost. In this environment, the OCXO will be exposed to vibration and temperature extremes. This change in deployment architecture requires new thinking and an evaluation of the benefits of MEMS and quartz timing technologies.”

Vashist continued: “Our unique systems approach is driving SiTime’s success in 200 applications at 10,000 customers. For example, our products are always programmable, which ensures 100% availability with short lead times. Our innovative temperature compensation algorithms, in conjunction with our MEMS and analog components, ensure that 5G equipment can be deployed anywhere, in any environment. In the future, we will continue to use our systems expertise to expand our leadership in the $1.5bn networking and telecommunications timing market.”

Solving the usability challenges of quartz OCXOs

Because of the sensitivity of legacy quartz OCXOs, customers have to take many precautions to ensure reliable operation. A key challenge is the board placement of the OCXO, which needs to be located far away from stressors such as heat and airflow-induced thermal shock. This results in increased routing complexity and potential signal integrity problems.

Designers have also tried using specialised plastic OCXO covers for thermal isolation, which introduces additional manufacturing steps and production complexity. Emerald MEMS OCXOs eliminate these problems; they simplify design, reduce development time, accelerate revenue, while improving system performance.

Flexibility through programmability

Legacy quartz OCXOs are custom built, from the ground up. There are severe limitations on the availability of features, such as frequencies, output types, operating temperature, and in-system control. SiTime’s Emerald Platform MEMS OCXOs do not have these limitations. Using a programmable analog architecture, the Emerald OCXO offers any frequency between one and 220MHz, ensuring that the customer can select the optimal frequency for their application.

The device also offers two output types, LVCMOS and clipped sine-wave, for optimal board performance. In the near future, the Emerald OCXO will also offer extended temperature operation (-40 to +95°C, -40 to +105°C) and an I2C serial interface for in-system programmability.

Technology highlights for the emerald platform SiT5711 & SiT5712 OCXOs:

(All comparisons are with quartz-based Stratum 3E OCXOs.)

• Ten times better performance in the presence of airflow and thermal shock.
  • ΔF/ΔT dynamic stability: ±50 ppt/C typical (ppt = parts per trillion).
  • Allan deviation (ADEV): 2e-11 under airflow.
• Unmatched ease-of-use.
  • No restrictions on PCB placement.
  • No mechanical shielding is required for thermal isolation.
  • On-chip regulators, no need for external LDOs or ferrite beads.
  • Resistant to humidity.
• Size: 9x7mm, 75% smaller. Adapter boards are available to match common OCXO footprints.
• Height: 6.5 mm, 40% thinner, eliminates obstruction in a chassis-based system.
• Twenty times better vibration resistance, ideal for outdoor pole mounted equipment.
• Resistant to microphonic and/or board bending effects, ideal for large telecom PCBs.
• Supports -40 to +85°C temperature range today, -40 to +95°C and -40 to +105°C support available in the near future.
• The only programmable OCXO platform, supports any frequency up to 220MHz and LVCMOS / clipped sine-wave outputs .
• Semiconductor-level quality and reliability, batch to batch consistency.
• No activity dips.

Samples of the Emerald MEMS OCXO SiT5711/12 are available now for qualified customers. Production quantities will be available in Q2 2019 and stocked at catalogue distributors such as Digi-Key and Mouser.