Make Your Next Design As Solid As A Rock

Silicon Labs offers XOs and VCXOs that use an internal multiplier PLL with a DSP filter for outputs in the 10-MHz to 1.4-GHz range (Fig. 6). The Si530 and Si550 are programmed by the manufacturer, while the Si570 is user programmable via an I2C bus. Stability options are from ±20 to ±200 ppm. The surfacemount package measures 5 by 7 mm.

OCXO_s put the crystal and sometimes the whole oscillator circuit in a small oven. A dc heating element in a feedback loop keeps the temperature virtually constant for very precise and stable output frequency. They are the best choice for critical applications like cellular basestations, telecom, local-area and wide-area networks (e.g., Sonet), and GPS.

Yet they draw much more power, with 1 to 3 W typical. The typical stability figure is ±1 × 10^-8. A typical aging rate is from about ±0.2 ppm/year to ±2.0 × 10^-8/year. Even improved accuracy and stability can be obtained with an OCXO that encloses one OCXO inside a second oven.

The type of oscillator you need depends specifically upon your application (see the table). David Meaney, engineering sales manager for Fox Electronics, says the highest crystal oscillator volume lies in cell phones and consumer products, followed closely by networking and computer- related applications. It’s essential to work closely with the crystal oscillator manufacturer to ensure you get exactly what you want and need.