Single-chip clock IC for wireless base stations

Paul Boughton

Silicon Labs has introduced what is claimed to be the industry’s most highly integrated clock IC for wireless infrastructure applications including small cell and macro cell base stations.

The Si5380 clock generator is the industry’s first clock IC capable of replacing a low phase noise integer-N clock, voltage-controlled crystal oscillator (VCXO), discrete loop filters and voltage regulator components with one single-chip device. The Si5380 clock provides comparable phase noise performance to discrete conventional solutions while delivering breakthrough advancements in solution footprint, bill of materials (BOM) cost, power consumption, performance and ease of use.

According to a recent Cisco study, global mobile data traffic will soar nearly 10-fold between 2014 and 2019, driven by video streaming services and the widespread adoption of IoT-connected devices. While base station suppliers are tasked with developing new 4G/LTE equipment that increases network capacity and coverage, it is becoming an increasingly difficult design challenge for small cells because they are often deployed in space-constrained, low-power outdoor locations in congested urban environments. Silicon Labs’ new Si5380 clock is the industry’s first single-chip wireless clock IC optimised for size, power, integration and performance, making it an ideal fit for small cell applications.

The Si5380 clock leverages Silicon Labs’ latest fourth-generation DSPLL technology to provide a purpose-built solution optimised for next-generation small cells and macro cell remote radio head (RRH) designs. DSPLL technology’s innovative dual-loop mixed-signal architecture integrates a single high-performance 15 GHz analog voltage-controlled oscillator within a digital phase-locked-loop (PLL) architecture that eliminates the need for discrete loop filters and low-drop-out (LDO) regulators. The resulting clock solution provides an optimal combination of ultra-low phase noise clock synthesis with best-in-class PLL integration.

The Si5380 clock has a 66% smaller printed circuit board (PCB) footprint and 30% lower power consumption than competing VCXO-based clock IC solutions. Power-efficient timing components are especially important for today’s small cells, which have limited power budgets and often are powered using Power over Ethernet (PoE) technology. Given that the DSPLL integrates all PLL and power supply regulation elements on-chip, the Si5380 device delivers high board-level noise immunity, integrated power supply noise rejection and consistent, repeatable phase noise performance across temperature.

While VCXO-based clock solutions often suffer from degraded spurious performance when subjected to vibration, the Si5380 device’s integrated DSPLL technology provides excellent spurious response regardless of the system environment. Furthermore, the Si5380 clock guarantees low phase noise operation when locked to a high jitter input clock, ensuring that data converter performance is not degraded by external effects. The Si5380 generates 4G/LTE frequencies up to 1.47456GHz and provides up to 12 independently configurable clocks, which can be used for clocking JESD204B-compliant data converters, FPGAs and other logic devices.

To simplify clock tree design for wireless base stations, Silicon Labs’ ClockBuilder Pro software enables designers to generate programmable Si5380 clock configurations in less than five minutes, minimizing software development overhead. Instead of waiting months for custom clock devices, designers simply upload their custom configurations to Silicon Labs through ClockBuilder Pro. Factory pre-programmed Si5380 clock samples ship in two weeks, accelerating the overall product development process with the industry’s shortest custom sample lead times.