Frequency Components Glossary

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Every Frequency Component Has A Job. Find Yours.

From passive crystals to temperature-controlled oscillators, covering all fields.

Passive Resonators

Quartz Crystal Resonator (XTAL)

A passive device that vibrates at a fixed frequency under electrical stimulation. It needs an external oscillator circuit to produce a clock signal. The workhorse cut is AT-cut, covering the MHz range.

Tuning Fork Crystal (32.768 kHz)

A low-frequency crystal shaped like a tuning fork, oscillating at 32,768 Hz. exactly 2(15) cycles per second. The universal choice for real-time clocks (RTC). Found in every device that keeps time while powered down.

Standard Oscillators

Crystal Oscillator (XO / SPXO)

An active device that packages a crystal resonator and oscillator IC into one unit. Apply power, get a clock signal. Typical stability: ±10 to ±100 ppm.

Differential Oscillator

An XO with differential outputs (LVDS, LVPECL, HCSL). Two complementary signals, 180° out of phase, for frequencies above 100 MHz where noise immunity matters.

Temperature-Controlled Oscillators

TCXO (Temperature Compensated Crystal Oscillator)

An XO with a built-in compensation circuit that corrects the crystal’s natural drift over temperature. Stability: ±0.05 to ±5 ppm. Used in GNSS receivers, telecom systems, and outdoor equipment.

VCXO / VCTCXO (Voltage Controlled Crystal Oscillator)

An oscillator you can tune by applying a control voltage. Pull range: typically ±50 to ±200 ppm. Used in PLL circuits and clock recovery.

High-Stability Oscillators

OCXO (Oven Controlled Crystal Oscillator)

A crystal oscillator housed in a miniature heated chamber at a constant temperature. This removes the largest source of frequency drift, delivering ppb-level stability. 100 to 1,000 times better than a TCXO. Used in base stations, test instrumentation, and satellite ground stations.

SAW Devices

SAW Resonator

A resonator that uses surface acoustic waves traveling across a piezoelectric substrate. quartz, LiTaO(3), or LiNbO(3). rather than bulk crystal vibration. Suited for high frequencies from hundreds of MHz into the GHz range.

SAW Filter

A frequency filter built on SAW technology. Interdigital transducers (IDTs) on the substrate select specific frequency bands while rejecting others. Essential in RF front-ends, mobile phones, and wireless modules.

Crystal Filters

Monolithic Crystal Filter

A filter with multiple coupled resonator sections fabricated on a single quartz blank. Offers narrow bandwidth with steep selectivity. Used in professional communications equipment and precision instrumentation where adjacent-channel rejection matters.

Every Number on A Datasheet is A Constraint on Your Design. Here is What Each One Means.

Key parameters explained. so you know which ones matter for your application.

Frequency Accuracy

ppm / ppb (Parts Per Million / Billion)

How far the actual frequency can deviate from nominal. 1 ppm at 10 MHz = 10 Hz. 1 ppb at 10 MHz = 0.01 Hz. ppb-grade stability calls for an OCXO.

Frequency Stability vs. Tolerance

Tolerance is initial accuracy at 25°C. Stability is the total deviation across temperature, voltage, load, and aging combined.

Frequency-Temperature Characteristic

The frequency-versus-temperature curve. AT-cut crystals follow a cubic curve with an inflection near room temperature. The slope steepens to the extremes. Understanding it is essential for wide-temperature designs.

Aging

Slow, permanent frequency drifts over time, measured in ppm/year. Caused by contamination migration and stress relaxation inside the package. Must be budgeted into any system with a field life exceeding five years.

Thermal Hysteresis

The frequency difference between heating-up and cooling-down at the same temperature. Matters for outdoor and cyclic-temperature applications

Retrace

How well the oscillator returns to its original frequency after a power cycle. Relevant for systems that power-cycle frequently or use standby modes.

Signal Quality

Phase Noise

Short-term frequency instability in the frequency domain, measured in dBc/Hz at a given offset from the carrier. Close-in phase noise (1 Hz to 1 kHz offset) affects PLL stability. Far-out phase noise (10 kHz to 20 MHz) affects broadband SNR and EVM.

Jitter

Time-domain instability of a clock edge. Three common types: Period Jitter (single-cycle variation), Cycle-to-Cycle Jitter (adjacent-cycle difference), and Integrated Phase Jitter (phase noise integrated over a specified bandwidth, e.g., 12 kHz to 20 MHz). A jitter spec only makes sense alongside its integration bandwidth. Always check the measurement conditions.

Allan Deviation (ADEV)

The RMS change between successive frequency measurements over a given averaging time τ. Converges for more noise types than standard deviation. ADEV at τ = 1 s captures short-term stability; τ = 100 s captures longer-term behavior.

Harmonics / Spurious

Unwanted frequency components at integer multiples of the carrier (harmonics) or at non-harmonic offsets (spurious). Harmonics affect EMI compliance. Spurious can cause PLL mis-lock or create unexpected mixing products in RF chains.

Electrical & Circuit Parameters

ESR (Equivalent Series Resistance)

The resistive loss inside a crystal, in ohms. Lower ESR means easier start-up. ESR rises in smaller packages. a 1.2 × 1.0 mm crystal will show higher ESR than its 5.0 × 3.2 mm equivalent.

Load Capacitance (CL)

The total capacitance the crystal sees from its two terminals, looking into the oscillator circuit. CL mismatch is one of the most common causes of frequency inaccuracy in new designs.

Drive Level

The power dissipated by the crystal during oscillation, typically 10 to 500 µW. Exceeding the maximum rating can cause permanent damage or accelerated aging. Tuning fork crystals are especially sensitive. even a modest overdrive can cause frequency jumps.

Q Factor (Quality Factor)

The ratio of energy stored to energy dissipated per cycle. Higher Q means lower phase noise (especially close-in) and better frequency stability. AT-cut quartz Q: 10,000 to 100,000. SC-cut can exceed 1,000,000.

Pullability / APR (Absolute Pull Range)

For VCXOs: the guaranteed controllable frequency range across all conditions. APR = Total Pull Range − (Tolerance + Stability + Aging).

Start-up Time

Time from power-on to stable oscillation. Standard XO: 2 to 10 ms. OCXO warm-up to specified stability: 2 to 5 minutes.

Waveform	Description
CMOS	Rail-to-rail single-ended, 1.8 to 3.3 V. Most common.
Clipped Sine	Reduced-swing single-ended. Lower EMI, well-suited for RF.
LVDS	Low-voltage differential, ~350 mV swing. Low power, good noise immunity. Common in networking.
LVPECL	Higher-swing differential, ~800 mV. Lower noise than LVDS but draws more power. Common in telecom infrastructure.
HCSL	Current-steering differential, ~700 mV. Used in PCI Express and server applications.
CML	Current-mode logic, open-drain differential. Common in high-speed telecom.

Environmental Parameters

Operating Temperature Range

The temperature window where all specifications are guaranteed. Common ranges: 0 to 70 °C (commercial), −40 to 85 °C (industrial), −40 to 125 °C (automotive Grade 1), −55 to 125 °C (military).

G-sensitivity

Frequency shift under acceleration or vibration, in ppb/g. Important for airborne, vehicle-mounted, and portable equipment.

Hermetic Seal

A package sealed against gas and moisture exchange. Tested per MIL-STD-883 Method 1014 (helium leak test). A failed seal lets in contaminants, accelerating aging.

DLD (Drive Level Dependency)

How frequency and ESR shift as drive level varies. High DLD can produce unexpected frequency changes when the oscillator circuit’s drive level varies with temperature or supply voltage.

Need help with a specific parameter? Talk to our application engineers

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A Component is Only as Reliable as The System Behind It.

The standards, certifications, and processes that turn a spec sheet into a dependable supply chain.

View certifications

Compliance & Certifications

EU directive restricting lead, mercury, cadmium, and other hazardous materials in electronic components. Mandatory for products sold in the EU.

EU regulation covering chemical substances. Requires full material disclosure for every part.

International standard for quality management systems. Certification means the manufacturer operates documented, auditable processes. from design through production to customer communication.

Environmental management system standard. Covers waste handling, energy use, and environmental impact across manufacturing.

Automotive Electronics Council stress test qualification for passive components. A crystal or oscillator marked AEC-Q200 has passed a defined battery of tests: temperature cycling, humidity bias, mechanical shock, and vibration. The de facto entry ticket for automotive Tier-1 and Tier-2 supply chains.

Production Part Approval Process. An automotive industry process (18 elements, from Design FMEA to Process Capability Studies) that proves a supplier can manufacture consistently at production volumes. A PPAP submission is typically required before a new component enters an automotive BOM.

U.S. military standard for microelectronics testing. Method 1014 covers hermetic seal testing; Method 2007 covers vibration. Referenced in aerospace and defense procurement.

Quality Assurance

Corrective and Preventive Action. A structured, eight-step problem-solving methodology: team formation → problem description → containment → root cause → corrective action → verification → prevention → close. When a quality issue is reported, 8D ensures it gets fixed and stays fixed.

Systematic investigation of a failed component to find root cause. May include X-ray imaging, cross-sectioning, SEM/EDX analysis, and electrical re-testing. An FA report tells you why the part failed. and whether other units are at risk.

Product Change Notification. Formal notice issued before changing a product’s materials, process, or design. Gives customers time to qualify the change or place last-time orders. A supplier with a vague PCN policy introduces hidden BOM risk.

End of Life. When a product is discontinued, the EOL notice specifies the last order date and last shipment date. Last Time Buy lets customers purchase enough inventory to cover remaining production needs.

A component that fails at incoming inspection or first power-up. DOA claims are typically resolved within days.

Three ways to quantify reliability: Defective Parts Per Million shipped, Mean Time Between Failures (hours), and Failures In Time (failures per billion device-hours). These are estimated from accelerated life testing and field return data.

Application Acronyms

Real-Time Clock. The always-on timekeeping circuit in every electronic device, driven by a 32.768 kHz crystal. Keeps time while the main processor sleeps.

Phase-Locked Loop. A circuit that generates a stable output frequency by locking to a reference clock, using a VCXO or TCXO as the tunable element. Critical for frequency synthesis in RF and clock generation.

Synchronous Ethernet. A standard for distributing frequency synchronization over Ethernet physical layers. Requires oscillators with tightly controlled frequency stability.

Precision Time Protocol. A network protocol for synchronizing clocks across packet networks to sub-microsecond accuracy. Places stringent demands on oscillator stability. particularly frequency-versus-temperature slope.

Global Navigation Satellite System. GPS, BeiDou, Galileo, GLONASS. A GNSS receiver uses a TCXO as its reference clock. Oscillator stability directly affects position accuracy and time-to-first-fix.

Serializer/Deserializer. High-speed serial interface. PCIe, Ethernet, USB, SATA. Requires an ultra-low-jitter reference clock. Jitter on the reference translates directly to bit errors on the link.

Electromagnetic Interference. Unwanted electromagnetic emissions from electronic circuits. Clock oscillators are a common source. the sharp edges of a CMOS clock generate harmonics that can exceed regulatory limits.

A clock that intentionally modulates its frequency (typically ±0.25% to ±2%) to spread EMI energy across a wider bandwidth, reducing peak emissions. Helps pass EMC compliance while keeping the original shielding and layout intact.

A mode where a synchronized system maintains frequency accuracy after losing its external reference. for example, during a GPS signal outage. Holdover performance depends primarily on the OCXO’s stability and aging characteristics.