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Quartz Crystal Oscillator ICs (XO), Crystal Clock Oscillators, and Low Power Oscillator Circuits

IDT offers quartz-crystal oscillators (XOs) and FemtoClock® NG programmable oscillator ICs to meet the needs of virtually any application. FemtoClock NG devices are the choice of the advanced system designer seeking a clock source with top performance and unmatched flexibility in a standard quartz crystal oscillator footprint. Using IDT's new 4th generation fractional feedback synthesizer architecture, the devices offer low phase-noise characteristics (<0.5 ps RMS) that are required for reference clocks in applications that cannot compromise in signal quality, conversion error and bit error rate. The linearity of the VCXO (voltage-controlled crystal oscillator) outperforms most existing tunable oscillators.


Fox Electronics, an IDT company, is a leading global supplier of frequency control products (FCPs). Fox’s low- power crystal oscillator product portfolio and leadership in the frequency control market, coupled with IDT’s frequency control products, and overall leadership in silicon timing, offer the industry’s most comprehensive one-stop shop for timing solutions and frequency control products. Click here to visit the Fox Electronics website, or click here to request Fox samples.

Fully Integrated Quartz crystal Oscillators

FemtoClock® NG 5 x 7 mm devices are quartz crystal oscillators that provide LVPECL, LVDS and LVCMOS clocks with frequencies from 15.48 MHz to 1300 MHz. The devices use IDT's 4th generation fractional-feedback PLL technology and integrate the crystal within the package. Each device features a set of up to four user-defined frequencies that are pre-programmed from the factory. An additional I2C programming interface allows access to internal PLL registers for reconfiguring the output frequency. The VCXO (voltage controlled crystal oscillator) devices also allow configuration of the absolute pull-range (APR) from ±7.5 to ±757.5 ppm. Compatible with the standard 6-pin 5 x 7 mm ceramic package, these devices are an ideal alternative to classic crystal clock oscillators, SO, VCXOs and VCSOs, with the additional benefit of a 4-pin interface for output frequency programming. The devices use standard outputs such as differential LVPECL, LVDS and single ended LVCMOS. These clock oscillators can be ordered with integrated crystals with an accuracy of ±20, ±50 or ±100 ppm.

Low-noise, Low-Power Crystal Oscillators

FemtoClock NG devices are low-power crystal oscillators that can be used in standard 5 x 7 mm quartz oscillator footprints. The phase noise performance of the FemtoClock NG 5 x 7 mm family enables their use as reference clocks for phase-noise sensitive applications. The low-power oscillators are ideal for clock generation where low phase-noise reference clocks improve transmission distance or reduce bit error rates and conversion errors of data transmission lines. Additional examples of application uses can be found in wireless infrastructure radio and base-band processing units, high-speed SerDes clocking (for instance S-RIO 1.3 and 2.1), PCI Express® Generation 1, 2 and 3, various Ethernet interfaces (Gigabit Ethernet, XAUI and 10 Gbit Ethernet), optical interfaces in SDH/SONET applications (OC-12, OC- 48 and OC-192) and in driving DAC/ADC devices in instrumentation applications.

Key Selection Criteria for Quartz Oscillator ICs

While physical footprints have tended to standardize, quartz oscillator ICs offer various features and levels of performance. Key attributes include:

  • output type: this is the signalling type of the output that is required of the crystal oscillator circuit. IDT offers LVCMOS, LVDS, and LVPECL.
  • output frequency range: the valid range of output frequencies. IDT offers quartz crystal oscillators to address the frequency needs of all popular applications.
  • core voltage: the supply voltage used to power the device. This is typically defined by the power rails available in the system, and often has implications on voltage levels of the output. IDT’s low-power oscillators are offered in both 2.5 V and 3.3 V options.
  • phase jitter: defined as the undesired deviation from an ideal periodic timing signal. IDT’s low-power oscillators offer typical RMS phase jitter of less than 500 fs, with some lower than 300 fs for very high-performance applications.

About Crystal Oscillators and Crystal Oscillator Replacement
A crystal oscillator circuit (or crystal clock oscillator) uses the mechanical resonance of a vibrating crystal or piezoelectric material to create an electrical signal at a precise frequency. This frequency is commonly used to provide a stable clock signal for digital integrated circuits within a system. The most common type of piezoelectric resonator used is the quartz crystal. In general, a crystal oscillator circuit sustains oscillation by accepting a voltage signal from the resonator, amplifying it, and feeding it back to the resonator. When the energy of the generated output frequency matches the losses in the circuit, the oscillation can be sustained. IDT offers thousands of timing products (such as quartz oscillator ICs / clock oscillators) to suit the needs of most applications.

Video: 5x7 Clock Overview