Wireless clocks support 4G/LTE and Ethernet applications

6th October 2017
Alice Matthews

Provider of silicon, software and solutions, Silicon Labs, has introduced a new family of high-performance, multi-channel jitter attenuating clocks for 4.5G and Ethernet-based Common Public Radio Interface (eCPRI) wireless applications. The new Si5381/82/86 clocks leverage Silicon Labs’ DSPLL technology to deliver an advanced timing solution that combines 4G/LTE and Ethernet clocking in a single IC.

These highly integrated clocks eliminate the need for multiple clock devices and voltage-controlled crystal oscillators (VCXOs) in demanding applications including small cells, distributed antenna systems (DAS), BTS, baseband units (BBU) and fronthaul/backhaul equipment.

Over the next several years, service providers will lay the groundwork for 5G by deploying small cells, pico cells, DAS, µ-BTS and backhaul equipment that complements existing 4G/LTE networks by increasing outdoor network coverage and capacity and improving indoor signal reception. As carriers transition to Ethernet-based eCPRI fronthaul networks to increase the capacity of fronthaul connections between base band units and remote radio heads, they are also deploying heterogeneous network (HetNet) equipment at the edge of the network where cost, power and size constraints present unique challenges for hardware designers. By combining 4G/LTE and Ethernet clocking in a single IC, the Si538x family dramatically simplifies HetNet clock generation, providing a solution that is supposedly 55% lower power and 70% smaller than competing solutions.

“HetNet and eCPRI equipment deployments are paving the way to 5G. By choosing Silicon Labs’ Si538x wireless clocks, wireless system designers can minimise the cost, power and complexity of small cells, DAS, BTS and other designs,” said James Wilson, Senior Marketing Director for Silicon Labs’ timing products. “Silicon Labs’ DSPLL-based Si538x clocks are the industry’s first timing ICs that combine low-phase-noise 4G/LTE clocking and low-jitter Ethernet clocking in the same device. We’re excited to see wireless customers adopting our technology to optimise HetNet designs and accelerate the deployment of 4.5G networks.”

The Si538x clocks are optimised to provide reference timing for HetNet equipment. Small cells and DAS equipment are 'all-in-one' base stations that need reference timing for 4G/LTE transceivers, baseband processing and Ethernet/WiFi connectivity. The Si5386 clock’s low-phase-noise DSPLL replaces a discrete clock IC, VCXO and loop filter components in a compact, single-chip design. In addition, the Si5386 clock integrates five MultiSynth fractional clock synthesisers to provide simplified Ethernet and baseband reference timing. According to the company this streamlined, single-PLL design provides superior reliability to alternate solutions that rely on multiple PLLs and discrete oscillators.

Baseband units have complex timing requirements requiring multiple independent clock domains for CPRI or links to remote radio heads, Ethernet-based eCPRI for fronthaul networks and general-purpose clocks for local baseband processing. The Si5381/82 clocks combine a high-speed, low-phase-noise DSPLL supporting wireless frequencies up to 3GHz with flexible any-rate DSPLLs optimised for Ethernet and general-purpose timing. Like the Si5386 clock, the Si5381/82 devices require no external VCXOs or crystals.

All PLL components are integrated on-chip in a space-saving 9x9mm 64-LGA package. In addition, the Si538x clocks support a hitless switching capability that enables system designers to easily switch between different clock inputs and minimise phase transients, ensuring downstream PLLs remain in lock. Like other clock products from Silicon Labs, the Si538x devices are configurable and customisable using Silicon Labs’ flexible ClockBuilder Pro software.

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