To limit interference and support higher throughput, 5G requires a different architecture than 4G networks. Instead of being located in remote cell towers, radios will be mounted on street lamps, traffic lights, rooftops and parking garages closer to smartphones and other connected devices. But to establish connections with each other, 5G radios needs to have precising timing—around 10 times more precise than 4G equipment.
That not only means boosting the precision of timing devices in telecommunications. It also means protecting their signals from vibrations, humidity, sudden temperature changes and other disturbances that can throw off frequency stability, said Piyush Sevalia, vice president of marketing at SiTime. The Santa Clara, California-based company is trying to check off both requirements to expand its share of the $1.5 billion wireless networking timing market.
On Monday, the company announced its first line of oven-controlled oscillators—more commonly called OCXOs—which have the lowest noise, highest precision and most stable performance over sudden changes in temperature of any timing component, making them critical to the operation of communications networks. Traditional OCXOs are used to keep time in the core network but could move into radios as timing requirements increase.
The Emerald timing devices are based on microelectromechanical systems (MEMS) instead of the tiny crystals traditionally used to generate timing signals that enable the operation of chips and circuit boards in almost every electronic device. That results in components that have 10 times stability over temperature than quartz OXCOs, according to SiTime. Sevalia said that they are also smaller and consume less power than alternatives.
“These components have been the realm of crystal oscillators for so long,” Sevalia said. Traditional OCXOs contain a sliver of transparent quartz that vibrates at a specific frequency when run through with electricity. The crystal is surrounded by a temperature-controlled oven. Limiting variations in ambient temperature serves to prevent unwanted changes in frequency. They generally range in price from around $10 to $100 each, according to SiTime.
But with the need for more accurate timing, 5G radio equipment could benefit from the use of OCXOs. The problem is that being mounted to street lamp poles or traffic lights can introduce the OCXOs to vibrations that throw off the resonance of the crystal, altering their frequency. Because SiTime’s MEMS components weigh only 1/3000th of crystal resonators, less energy couples to them, resulting in higher vibration resistance, Sevalia said.
“It was just a matter of time before we got here, and now here we are,” he said. In addition to alternatives for oven-controlled crystal oscillators, SiTime is also targeting customers that typically use voltage-controlled crystal oscillators (VXCOs) that output different frequencies based on the input voltage, temperature-compensated crystal oscillators (TCXOs) that can better tolerate heat fluctuations, and standard crystal oscillators (XOs).
Business has been booming. SiTime’s products are stealing market share in factories, cars and other systems subject to extreme temperatures, violent vibrations and other stressors, even though they generally cost more than crystal devices. Last year, under chief executive Rajesh Vashist, the company increased unit shipments around 85 percent to 425 million. That gave the company more than a billion units shipped since it was founded in 2005.
SiTime’s Emerald product line is based on a programmable analog architecture, allowing the company to program the timing devices to any output frequency between 1 and 220MHz based on customer demands. The devices support temperature operation from -40 to 85°C. Before the end of the first quarter of 2019, SiTime plans to give customers the ability to program the devices themselves and to broaden the temperature range to 40 to +105°C.
Since SiTime’s Emerald products are less vulnerable to temperature and vibration, customers have more freedom in the layout of circuit boards and can avoid using additional shielding for thermal isolation. The timing devices are also smaller than alternatives, so the company is planning to sell products that match the dimensions of common OCXOs. That way, customers can use them like drop-in replacements, Sevalia said.
“With 5G, every radio may need an OCXO,” he told Electronic Design. Potential customers could include Ericsson and Nokia, which are both building 5G radio access equipment for global deployments. Last month, the companies said that they were using multimode wireless chips from Intel, which previously said that it would use SiTime's silicon to keep time in its wireless modems for 5G infrastructure.