Family Overview

The FCX and FSX MHz crystal families, together with HC-49 packages, are built for industrial control and embedded computing systems that must keep clocks stable across temperature swings, electrical noise, and long operating lifetimes. Typical targets include control CPU/MCU clocks, FPGA reference clocks, and interface timing for Ethernet/fieldbus and wireless modules.

In industrial environments, the crystal is more than a frequency reference—it impacts oscillator start-up margin, EMC/EMI behavior, communication stability, and system reliability. FCX/FSX/HC-49 options provide practical trade-offs among footprint, mechanical robustness, and sourcing continuity.

Industrial Control & Embedded Application Focus

PLCs, Motion Control & Robotics

In PLC CPUs, servo drives, and motion controllers, MHz crystals commonly support MCU/MPU clock domains, FPGA logic clocks, and peripheral timing. Stable oscillation over temperature helps maintain deterministic behavior and reduce unexpected communication faults during cold start or cabinet heating. Compact SMD packages are often preferred for dense controller cards, while more rugged packages are common in high-vibration or heavy-cabinet systems.

Industrial Gateways, Routers & Edge Computing Boxes

Industrial gateways and edge computers typically integrate Ethernet PHYs, Wi-Fi/LPWAN modules, and multi-protocol interfaces. MHz crystals support reference clocks and system clocks used by SoCs and communication subsystems. For designs that run 24/7 in plants, warehouses, and outdoor enclosures, wide-temperature stability and lifecycle management are key selection drivers.

Industrial Ethernet, Fieldbus & TSN Networks

Multi-port industrial Ethernet switches and fieldbus controllers depend on stable reference clocks to keep link timing and protocol stacks reliable. While absolute telecom-grade frequency accuracy is not required, sufficient stability and low start-up risk improve real-world uptime. Common design practices include keeping the crystal loop tight, using clean ground, and verifying start-up margin across temperature and component tolerances.

Power Electronics, Inverters & Energy Systems

In UPS controllers, DC/DC converters, motor drives and inverters, crystals often live near noisy switching nodes. Good layout discipline (short traces, ground shielding, separation from high dV/dt nets) and mechanical robustness are critical. Through-hole or metal-can options may be preferred for specific assemblies or harsh vibration scenarios.

Test & Measurement Instruments

Measurement devices in factories and labs use MHz crystals for microcontroller timing, digital interface clocks and control loops. Stable oscillation improves firmware timing accuracy, trigger consistency and long-term reliability—especially when instruments are exposed to variable ambient temperatures or continuous operation.

Key Series and Packages

FCX Series – Recommended for New Industrial Designs

FCX series SMD crystals are designed for modern industrial and embedded projects requiring compact size, solid ESR margin and long-term support:

• FCX-3M – 3.2 × 2.5 mm SMD, general-purpose system clock for MCU, MPU and PHY.
• FCX-2M / FCX-2S – 3.2 × 2.5 mm SMD variants with different load capacitance and stability options.
• FCX-1M / FCX-1S – 5.0 × 3.2 mm SMD packages for boards that prefer larger pads and easier routing.
• FCX-5M / FCX-7M / FCX-9M – smaller footprint options for dense embedded modules and communication cards.
• FCX-M1 / FCX-M5 – additional industrial MHz crystal options for legacy compatibility and new designs.

FCX crystals are recommended for new industrial control and embedded platforms as the main timing reference for microcontrollers, FPGAs, SoCs and interface PHYs.

FSX Series – Legacy Industrial SMD Crystals

FSX crystals support existing designs in volume production or long-term field operation, where platform continuity and re-qualification cost are critical:

• FSX-3M – 3.2 × 2.5 mm SMD crystal for legacy 8–80 MHz system clocks.
• FSX-2M / FSX-2MS – options for mid-size control boards.
• FSX-5L / FSX-5M – larger SMD footprints for robust soldering and easier layout.

For most new designs, FCom recommends migrating from FSX to the corresponding FCX series to secure a clearer long-term roadmap, while keeping PCB-level compatibility where possible.

HC-49 / HCM49 Series – Through-Hole and Wide-Body Crystals

For large industrial boards and cabinet-mounted equipment, classic through-hole and metal-can crystals remain popular due to mechanical robustness, inspection convenience, and mixed assembly workflows:

• HC-49S – standard through-hole crystal for general-purpose timing in control units.
• HC-49US – low-profile through-hole variant where height is constrained.
• HCM49S – SMD-compatible metal-can crystal for ruggedized boards and mixed-assembly lines.

These packages are well suited for power cabinets, protection relays, rack equipment, and legacy industrial systems where PCB area is less critical than mechanical robustness and ease of maintenance.

Recommended FCom MHz Crystal Series

The table below lists representative FCX, FSX and HC-49 series that are commonly used in industrial control and embedded applications.

Typical Electrical Performance

Exact specifications depend on the selected part number and frequency, but typical industrial MHz crystal characteristics include:

• Frequency range from single-digit MHz to tens of MHz, such as 8–80 MHz.
• Frequency tolerance from ±10 ppm to ±30 ppm at 25 °C, depending on grade.
• Frequency stability over −40 °C to +85 °C or −40 °C to +105 °C for industrial use.
• Series resistance (ESR) optimized for fast start-up with common MCU and SoC oscillator circuits.
• Load capacitance options aligned with standard 10 pF, 12 pF, 18 pF and custom targets.

These parameters provide reliable operation for industrial Ethernet/fieldbus interfaces, wireless connectivity modules, control processors and instrumentation logic in industrial settings.

Representative Industrial & Embedded Applications

• PLCs, motion controllers, servo drives and industrial automation I/O modules.
• Industrial gateways, routers, CPE and edge computing boxes for IIoT connectivity.
• Embedded Linux platforms, SOM/COM carrier boards, HMI panels and sensor hubs.
• Rack-mounted power systems, UPS controllers, inverters and DC/DC converters.
• Test and measurement instruments used in factories and labs.
• Legacy control and protection equipment in power and utility networks.

If you are designing for long service life, broad operating temperature, and stable communication behavior in harsh environments, choosing the right MHz crystal package and grade is a practical way to improve uptime and reduce field returns.

Design Guidelines for Industrial MHz Crystals

• Match the load capacitance. Choose the crystal CL to match the oscillator circuit (internal and external capacitors), minimizing static frequency error.
• Check negative resistance margin. Aim for a negative resistance at least five times the ESR to guarantee start-up over temperature and component tolerances.
• Use a solid ground reference. Place the crystal close to the oscillator pins, with a continuous ground under the loop to minimize EMI and improve stability.
• Separate from switching noise. Keep the crystal network away from power MOSFET gates, switching nodes and high dV/dt nets in inverters, drives and power supplies.
• Consider mechanical stress. For high-vibration environments, prefer shorter SMD packages or rugged metal-can options with proper board support and mounting.
• Plan for lifecycle management. When upgrading or redesigning existing equipment, consider moving from FSX to FCX series to secure long-term availability.

FAQ – Industrial & Embedded MHz Crystal Family