An all-silicon quartz crystal replacement with all four desirable characteristics – accuracy, small size, low power, and low cost – is the claim of fabless start-up eoSemi of Congleton Cheshire. It is sampling its first product: a 1.5×1.5mm 32kHz timing reference chip for mobile phones.
Manufactured using a standard CMOS process, it draws 8µA and delivers accuracy down to ±30ppm. Engineering samples have been delivered, and commercial production is due in Q3.
This combination of specifications, with an operating temperature range of -40°C to 85°C, means that the timing reference will comply with the system design requirements of major 3G handset manufacturers, claimed the firm.
Its IP, accurate timing oscillator circuit (Atoc), does not involve physical resonators, micromachined or otherwise, nor squeezing every last error out of the oscillator. It is about error compensation – going so far as to correct for stress in the silicon chip substrate. “We have a technique for tuning oscillators, it could be any oscillator: RC or LC,” said CEO Ian Macbeth. “All the smarts are in the compensation, not the oscillator.”
After manufacture, calibration codes to be applied at power-up are blown into non-volatile memory. Plus there is some continuous re-calibration.
Phone-makers want the product, claims Macbeth, but want to cut the risks associated with small start-ups. Desire was strong enough for phone makers to ask big chip firms to come up with a solution, so eoSemi is having its chips made by a trusted supplier – TSMC, and badged by Tier 1 chip firms.