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Understanding Oven-Controlled Crystal Oscillators (OCXOs)

oscillator frequency control ocxo timing crystal

An Oven-Controlled Crystal Oscillator (OCXO) is a sophisticated type of oscillator designed to generate a highly stable frequency. At its core, it utilizes a crystal resonator, but what sets it apart is the “oven-controlled” aspect. This means the crystal and related components are housed within a temperature-controlled oven.

The primary function of this oven is to maintain a consistent temperature for the crystal. This is crucial because the frequency of a crystal oscillator can be affected by temperature fluctuations. By keeping the temperature stable, the OCXO minimizes frequency variations, ensuring precise timing in demanding applications.

OCXOs find widespread use in a variety of fields, including:

  • Telecommunications
  • Military
  • Aerospace
  • Industrial equipment
  • Scientific instruments

In these areas, precise and stable timing is not just desirable – it’s essential.

Key Specifications to Consider

When selecting an OCXO for a specific application, several key specifications should be carefully considered:

  • Frequency Stability: Measured in parts per billion (ppb), this indicates how stable the output frequency is.
  • Aging Rate: Expressed in ppb per day, this shows how much the frequency drifts over time.
  • Temperature Stability: Measured in ppb over the specified operating temperature range, this indicates how much the frequency changes with temperature variations.
  • Operating Temperature Range: The range of temperatures over which the OCXO will maintain its specified performance (e.g., -40°C to +85°C).
  • Control Voltage: The voltage used to fine-tune the oscillator’s frequency.
  • Aging Characteristics: Look for OCXOs with low aging rates for long-term stability.
  • Phase Noise: Low phase noise is crucial for achieving good frequency stability.
  • Warm-up Time: The time it takes for the oscillator to stabilize after being powered on.
  • Package Type: Choose between surface-mount or through-hole packages based on your design requirements, considering the dimensions.
  • Power Supply: Consider the operating voltage and power consumption of the OCXO.
  • Output Type: Select the appropriate output signal type (sine wave, HCMOS, etc.).
  • Other Features: Programmability, digital frequency control, and other specialized functionalities may be important for your application.

OCXO Manufacturers and Their Offerings

Here’s an overview of some leading OCXO manufacturers and examples of their products:

SiTime OCXO

SiTime specializes in MEMS-based oscillators and timing solutions, offering OCXOs with high stability and low phase noise.

  • Part Numbers: SiT5711 and SiT5811
    • Support frequencies of 1 MHz and 60 MHz respectively.
  • Website: sitime.com

Bliley OCXO

Bliley Technologies provides precision frequency control devices, including OCXOs, for satellite communication, military, and wireless applications.

  • Part Numbers: BOVXJ-XXXMXX-XXXB and BOVTF-10MDB-ECAB
    • Support a frequency range of 5 to 100 MHz.
    • Various models with different frequency outputs and packages are available.
  • Website: bliley.com

Rakon OCXO

Rakon is a global manufacturer of frequency control solutions, including OCXOs, used in telecommunications and aerospace.

  • Part Numbers: ROD2522S2
    • Supports standard frequencies (10, 12.8, and 20 MHz).
    • Offers 0.5 ppb frequency stability over a temperature range of -40 to 85°C.
  • Website: rakon.com

Abracon OCXO

Abracon provides a wide range of frequency control and timing components, including OCXOs, for automotive, industrial, and telecommunications applications.

  • Part Numbers: AOC1409 and AOC2012
    • SMD oven-controlled SC-Cut crystal oscillators with high precision clocking and ultra-low phase noise.
    • AOC1409: 20 MHz frequency output.
    • AOC2012: 10 to 25 MHz frequency output.
    • Both support a Vdd supply of 3.3V.
  • Website: abracon.com

Wenzel OCXO

Wenzel Associates manufactures precision crystal oscillators, including OCXOs, used in instrumentation, communication, and aerospace.

  • Part Numbers: Various models are available for different frequency outputs, including:
    • Vibration Isolated HF Citrine (10 MHz to 25 MHz)
    • Vibration Isolated HF Citrine Plus (1 MHz to 125 MHz)
    • Vibration Isolated VHF Citrine (25 to 160 MHz)
    • Vibration Isolated VHF Citrine Plus (50 MHz to 700 MHz)
  • Website: quanticwenzel.com

Vectron (Microchip Technology Inc.) OCXO

Vectron International (now part of Microchip Technology Inc.) produces precision oscillators and timing solutions.

  • Part Numbers: Microchip offers various models.
    • Frequency range: 10MHz to 49.152 MHz.
    • Frequency stability: 10-20 PPB.
    • Operating supply voltage: 3.3VDC.
    • Operating temperature range: -40°C to +85°C.
  • Website: microchip.com