Crystal Oscillators combine TCXO and OCXO functionality.

Press Release Summary:

With output frequencies from 5-20 MHz, CFPO-20 series temperature-compensated oven-controlled crystal oscillators (TC-OCXOs) offer stabilities within ±0.025 ppm over -20 to +70°C and consume under 400 mW of power. Miniature oven keeps XO at constant temperature and compensates for residual temperature-related frequency errors using Pluto compensation technology. Products are manufactured in 20.7 x 13 mm DIL package and operate from 3.3 or 5.0 V supply.

Original Press Release:

C-MAC's First TC-OCXOs Deliver ±0.025 ppm Over Temperature in a Standard 20.7 x 13 DIL Package

First commercial products based on proprietary TC-OCXO technology

Durham, NC, July 2005 - C-MAC MicroTechnology has introduced the first commercial products based on its proprietary TC-OCXO (temperature-compensated oven-controlled crystal oscillator) technology. Designed to combine the high stability of an OCXO with the comparatively low power consumption, small size and light weight of a TCXO, the new CFPO-20 series TC-OCXOs offer stabilities to within ±0.025 ppm over operating temperature, with output frequencies between 5 and 20 MHz.

The CFPO-20 series is aimed primarily at mobile, battery powered and remote applications such as GPS, satellite communications and secure radio. These applications commonly use both TCXOs - small, low-power yet high-stability frequency reference sources - and OCXOs - offering stabilities at least an order of magnitude better but with greater package size, power consumption and cost.

The CFPO-20 series combines the best characteristics of TCXOs and OCXOs by using a simple miniature oven to keep the crystal oscillator at an approximately constant temperature, slightly above its specified operating temperature range, and compensating for residual temperature-related frequency errors using C-MAC's Pluto compensation technology.

As a result, the CFPO-20 series offers stability down to ±0.025 ppm (2.5 x 10-8) over the -20° to +70°C operating temperature range, or ±0.05 ppm (5 x 10-8) for -40° to +85°C, from a 3.3 or 5.0 V supply, in an industry standard 20.7 x 13.08 mm DIL package. Power consumption is less than 400 mW or 525 mW, respectively, for the above operating temperature ranges, at -20°C steady state.

Standard output frequencies are 5, 6.4, 8 and 8.192 MHz with square HCMOS output, and 10, 12.8, 16, 16.384 and 20 MHz with either square HCMOS or AC-coupled clipped sinewave output. Other frequencies in the range from 1.25 to 33 MHz are available to certain specifications upon request, as are square ACMOS and DC-coupled sinewave outputs.

The crystal ageing effect over 10 years is specified to within ±3 ppm for output frequencies up to 20 MHz and ±5 ppm for frequencies above 20 MHz, with frequency adjustment of ±5 ppm or ±7 ppm, respectively, available to compensate for ageing.

"Particularly in portable applications it is of paramount importance to minimize battery consumption, package size and cost," said Karl Ward, Senior Design Engineer with C-MAC Frequency Products. "Designers welcome any component that lends a helping hand, and the CFPO-20 is a ground breaker, combining stability approaching that of an OCXO with power, size and cost more like those of a TCXO."

About C-MAC MicroTechnology:

C-MAC MicroTechnology specialises in the design and manufacture of high-reliability products. With design and manufacturing facilities in the UK, France, Belgium and Canada and additional dedicated sales offices within Europe, the USA and China, C-MAC MicroTechnology serves the military, aerospace, transportation, medical, industrial and communications equipment sectors, and has built up an extensive portfolio of intellectual property resources and an impressive electronics design and manufacturing pedigree geared specifically to these industries. C-MAC's products are usually found in applications that operate in harsh environments, often at extremes of temperature or frequency. C-MAC MicroTechnology comprises two business units: C-MAC MicroSystems Solutions and C-MAC Frequency Products.

C-MAC Frequency Products has a 70-year history of manufacturing quartz-based frequency control products and now has four design, engineering, manufacturing and sales centres in Crewkerne, Harlow and Lincoln, UK, and Argenteuil, France. Its product range encompasses AT and SC cut crystals, crystal oscillators, voltage controlled crystal oscillators (VCXOs), temperature compensated crystal oscillators (TCXOs), oven controlled crystal oscillators (OCXOs), and rubidium oscillators and clocks. Particular specializations include patented ASIC-based high-stability TCXOs, ultrastable OCXOs and SDH/SONET reference oscillators.

About Pluto:

C-MAC's proprietary temperature compensation technology, known as Pluto, allows TCXOs with stability as good as ±0.3 ppm (parts per million) over their operating temperature range - or even better for certain frequencies - to be implemented within a standard 7 mm x 5 mm ceramic package. Although implemented on a silicon die measuring just 3.2 mm x 2.3 mm, Pluto crams in an unprecedented degree of frequency control functionality. The basic function is digitally controlled analogue temperature compensation of output frequency, which is achieved to a high degree of accuracy by applying four orders of Chebyshev polynomials to the signal. Pluto incorporates circuitry that allows either the crystal's fundamental frequency or its third overtone to be selected. This enables an oscillation frequency range in excess of 10-80 MHz, with output CMOS frequencies of less than 10 MHz achievable by means of an on chip divider.

About C-MAC TC-OCXO technology:

C-MAC's TC-OCXO approach, for which patent protection has been applied, takes the output of a crude OCXO and applies TCXO compensation to it. A miniature oven keeps an uncompensated crystal oscillator at an approximately constant temperature slightly above the specified operating temperature range, e.g. between 90° and 95°C for an operating temperature range of -40° to +85°C. Because the oven does not have the strict temperature requirements demanded by a conventional OCXO, it can be implemented at much lower cost and in a smaller package. The whole assembly is then treated as a TCXO. A temperature sweep is performed at the factory and each device programmed with a correction curve generated in the thermally stable environment it will be used in, i.e. with the oven on. In effect, the TC-OCXO performs like a TCXO that experiences only a few degrees of temperature fluctuation. A Pluto device is used to perform the necessary temperature compensation because its fully programmable analogue compensation allows a smoother output than a conventional programmable digital TCXO, because its single-pin programming interface allows the oven environment to be sealed before programming, so the correction curve can be optimised in a stable environment, and because it incorporates circuitry to linearize the voltage control curve of the oscillator, making it ideal for digital control and phase-lock loop applications.

Further information:

Jan Ooijman, C-MAC MicroTechnology. Tel: +44 (0)1279 774465. Fax: +44 (0)1279 774488. Email:

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Issued by:

Janet Kingston, C-MAC MicroTechnology. Tel: 703-472-5372. Fax: 540-668-7108. E-mail:

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