Crystal oscillators provide the critical timekeeping needed in many electronic systems. These low-frequency reference sources must deliver unfaltering frequency and phase stability, even taking into account the temperature swings and vibration found in mobile and portable electronic products during normal operation. To offer all this in a series of temperature-compensated crystal oscillators (TCXOs) that also operates with extremely low current/power consumption, Greenray Industries has developed their T72 Series TCXOs with output frequencies from 10 to 50 MHz. With frequency stability as good as 0.2 ppm across an operating temperature range of -40 to +85C, the T72 Series oscillators can deliver clipped sine wave outputs when running on a mere 1 mA current from a +3.3-VDC supply. For battery-powered and/or portable electronic applications, this low-power operating capability translates into extended run times without relying on oversized power sources.
The T72 Series TCXOs are encased in a compact but rugged 5 x 7 mm ceramic package (see figure). The oscillator housings hold precision quartz crystals from sister company Statek Corp. to enable outstanding frequency stability over a wide range of environmental conditions. For example, although sensitivity to acceleration force (or "g-sensitivity") might more typically be associated with airborne applications, the effects of acceleration forces can impact portable electronic applications such as Global Positioning System (GPS) receivers and tracking equipment used in vehicular and ground-based electronic systems. The T72 Series TCXOs feature standard g-sensitivity of better than 2.5 x 10-9/g. And for those applications where g-sensitivity might be a concern, a low-g-sensitivity option for the T72 Series oscillators promises performance of better than 7 x 10-10/g. The precision quartz crystals from Statek also translate into low phase noise, with a typical phase noise floor of -159 dBc/Hz measured at a 10-MHz carrier frequency.
The T72 Series OCXOs generate a typical sine wave output level of +0.8 V peak to peak into a 10 pF/100 kO load. CMOS-level oscillators will also be available as an option. A number of different temperature stability options are available to cover a wide range of requirements. While the basic oscillator circuits are the same for these different options, the Statek crystals are sorted by characteristics to create TCXOs with different temperature stability profiles.
Option G17 provides a frequency tolerance within 0.1 ppm for operating temperatures from -10 to +60C, while option N17 promises frequency tolerance within 0.1 ppm for operating temperatures from -10 to +67C. Options T27 and T37 are somewhat more relaxed in terms of stability, with frequency tolerances of 0.2 and 0.3 ppm, but for a much broader operating-temperature range of -40 to +85C. Meanwhile, option V16 offers frequency tolerance within 1.0 ppm over an operating-temperature range of -55 to +95C.
With their low power consumption, the T72 Series TCXOs are ideally suited for numerous portable applications. They feature an aging rate of typically less than 1 ppm/year for a 10-MHz oscillator. For fine tuning, the frequency of the TCXOs can be adjusted by typically as much as 7 ppm by means of the control voltage (Vcc). In addition, the TCXOs offer electronic frequency control (EFC) for phase-locking applications. The rugged TCXOs are vibration and shock tested per MIL-STD-202G, with shock testing performed at levels to 50,000 g's. Additional performance data is available upon request.