PCIe compliant clock generator is 'industry's smallest'

6th October 2014
Siobhan O'Gorman

A PCIe compliant clock generator, designed for applications where reliability, board space, component count and power consumption are essential, has been released by Silicon Labs. The Si50122, which is suitable for consumer and embedded applications, is claimed to be the industry's smallest PCIe compliant clock generator.

To offer an energy-efficient, crystal-less timing solution for a wide range of applications, the PCIe clock utilises Silicon Labs’ PCIe and CMEMS technologies. Suitable applications include digital video and still cameras, IP set-top boxes, HD streaming video players, HD digital TVs, home entertainment and audio systems. The clock can also be used for multi-function printers, consumer and small-business storage, and home gateway and wireless access equipment.

The need for quartz crystal is removed by the CMEMS resonator, which provides a stable frequency reference to the device’s CMOS clock circuitry. With the CMEMS technology, the Si50122 PCIe clock provides reliable and rugged performance, as well as shock and vibration resistance. By using a CMEMS PCIe clock generator rather than a crystal-based solution, the risk of system failure is reduced as a CMEMS resonator is less likely to break.

The Si50122 PCIe clock features a low-power push-pull HCSL output buffer, which removes the need for external termination resistors at the HCSL outputs. Up to four termination resistors per output and a current source resistor are required by competing clock generators which use a legacy output buffer architecture. Designers, therefore, have to manage up to nine external resistors for a two-output device. Push-pull technology provides cleaner signal integrity as it removes a number of external components, enabling designers to create a continuous transmission line from the output pin to the receiver. With push-pull technology, the clock generator consumes 60% less power than those using constant-current technology.

Two 100MHz differential HCSL outputs and one 25MHz LVCMOS clock output are provided by the clock. As the clock generator is crystal-less, it does not require an external 25MHz frequency source. The Si50122 PCIe clock, which exceeds the jitter requirements for the PCIe Gen 1/2/3 standards, supports optional spread spectrum modulation for EMI reduction.

“As today’s power- and space-constrained consumer and embedded products continue to adopt the PCIe standard, developers need next-generation PCIe clocking solutions that minimise power consumption, BOM count and board size,” said James Wilson, Director of Marketing for timing products, Silicon Labs. “We designed our CMEMS-based crystal-less Si50122 PCIe clock to provide the utmost in integration, energy efficiency, reliability and design simplicity for the rapidly expanding PCIe market.”

The PCIe clock, which is offered in a 2x2.5mm 10-pin TDFN package, is not only claimed to be the industry's smallest but also the industry's lowest power crystal-less clock. The clock is, therefore, particularly suitable for space-constrained, handheld and battery-powered consumer and embedded applications that are acquiring the PCIe interconnect standard. The Si50122 PCIe clock is sold in 10,000 quantities and priced from at $0.77.Si50122-Ax-EVB evaluation boards, which are priced at $125, are also available to use alongside the clock.

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