eoSemi's silicon timing package: 'Cheaper, smaller and more robust than quartz'

All-silicon oscillator targets stress relief in cellphone clocks

A British startup has developed a silicon technology that it believes can prise a large chunk of an $800m market away from quartz oscillators.

EoSemi is using a novel partnership approach to overcome resistance from large customers unwilling to do business with young, small companies.

Electronics manufacturers are trying to find alternatives to quartz, which has been in use for close to a century, because of the space the crystal and its surrounding circuitry take up.

“The most common crystal used today in mobile phones measures 3.2mm x 1.5mm,” said Steve Cliffe, vice president of sales and marketing at eoSemi, adding that the sensitive nature of the crystal means designers have to keep other components away from the package as well as adding support capacitors, which all increase the effective size some way beyond the basic package measurements.

Cliffe said eoSemi’s 1.5mm x 1.5mm silicon-based oscillator could be mounted in the same package as other integrated circuits to cut PCB space.

Other companies, such as Maxim Integrated Products and Silicon Laboratories, have launched silicon oscillators as low-cost alternatives to quartz. The electrical oscillator circuits are relatively inaccurate – the frequency can vary by thousands of parts per million (ppm) – but can be digitally corrected.

Cliffe said: “Semiconductor companies have pulled the accuracy to 100ppm by correction. But, so far, they have only taken care of temperature-related changes. Other stresses affect the circuit, which you can get just by bending in the PCB. We have seen as much as 1,000ppm due to stress that’s not related to temperature. One thousand ppm – that’s almost 90 seconds a day. It’s a big number and it means you can’t use the oscillator in a mobile phone, because that depends on an accurate timing reference. I think we are the first on the planet to take care of this.”

Cliffe said the company has had to find a novel way to approach mobile-phone makers that favour buying components from well-established suppliers. The company’s first product, a 32kHz timing reference circuit, is aimed at this market.

“You talk to the top 15 mobile companies and none of them will do business with you,” said Cliffe. “We are looking to partner with tier-one semiconductor companies who already sell into that market. We will provide the manufacturing rights to make these products – they can make the devices themselves or take ours and put them in the same package as, for example, a power-management chip, and sell those on. Fundamentally we are not a licensing company, but this is a way of getting into the marketplace.”

Ian MacBeth, co-founder and CEO of eoSemi, added that power consumption is another area where the firm has the edge: “Most of the oscillator solutions have their power supply currents measured in milliamps. Ours is measured in microamps: milliamps are for mobile phones. We needed to drive that down. It is a fairly vanilla oscillator in there with low power. It’s the surrounding circuitry that makes all the difference.”

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