FCX-1S is built for compact RF and digital systems where PCB area is the dominant constraint. The seam-sealed, vacuum package improves environmental robustness and helps maintain stable characteristics over storage and operating life.

Typical design targets include wireless modules (Wi-Fi / Bluetooth / LPWAN), wearable devices, smartphones, and space-limited consumer electronics where a discrete resonator is used as the reference for a PLL or an MCU clock tree.

The values on this page reflect common catalogue configurations. Final delivered specifications depend on the confirmed part suffix and the latest official datasheet.

Where it sits in the clock tree

• RF SoC / MCU reference clock (XTAL input) for PLL synthesis
• Wireless module local reference for channel accuracy and timing
• Wearables compact clocking in always-on domains

For portfolio navigation, see: Quartz Crystal Resonators, Frequency Crystals and Timing Devices.

Engineering Highlights

• Nominal frequency range: 24–76.8MHz.
• Frequency tolerance: ±10ppm @25°C (typical option).
• Wide temperature stability options: ±15ppm (−40~+85°C), ±30ppm (−40~+105°C), ±80ppm (−40~+125°C).
• Load capacitance options: 6 / 10 / 18pF (custom CL available).
• Drive level guidance: 10µW typical, 100µW max (validate with your oscillator gain setting).
• ESR limits defined by frequency band to support start-up margin validation.

Common Reference Frequencies

• 24 / 26MHz — often used as reference clocks for connectivity modules and RF SoCs (confirm chipset CL and drive).
• 38.4MHz — commonly used in cellular and mixed wireless platforms where a stable high-frequency reference is required.
• 40MHz — frequently adopted for Wi-Fi / high-throughput connectivity platforms (verify start-up margin vs ESR band).

The exact “common frequency” depends on your chipset and BOM strategy. Always lock the final frequency and CL against the IC vendor reference design.

Production & Compliance

• Industry standard footprint: 1.2×1.0×0.33mm SMD.
• Seam-sealed with vacuum for enhanced reliability and moisture resistance.
• Reflow compatible, optimized for automated SMT assembly.
• RoHS & REACH compliant, Pb-free documentation available.
• Lot traceability support for qualification and mass production.

Load Capacitance Selection (CL)

Choose a crystal CL that matches the effective load at the IC pins: CL ≈ (C1·C2)/(C1+C2) + Cstray. For symmetric Pierce networks, C1 ≈ C2 is common.

• If your SoC uses internal programmable caps, include their settings and PCB stray capacitance in the estimate.
• When uncertain, validate two adjacent CL options (e.g., 10pF and 18pF) during EVT.
• Keep the layout symmetric to reduce differential stray mismatch and spurs.

Start-up Margin, ESR & Drive

• Check oscillator negative resistance margin against the crystal ESR (common rule: ≥5× margin).
• Use the ESR band that matches your target frequency (see table below) rather than a single “60~100Ω” bucket.
• Control drive level: excessive drive can increase aging and long-term drift, especially in ultra-small packages.
• Place FCX-1S close to XTAL pins; keep traces short, avoid vias, and keep away from DC/DC and high-speed clocks.

For deeper debug guidance (loop gain, startup sweeps, and failure analysis), contact FCom engineering.

Mechanical

Pin labeling may vary by drawing revision. Many 4-pad SMD crystals use two active pads for the resonator and dedicate the remaining pads to case ground or NC. Follow the latest FCX-1S datasheet for your exact pin assignment.

Suggested PCB Land Pattern (Reference)

The catalogue drawing shows a symmetric 4-pad land pattern. Use your PCB stack-up and assembly capability to finalize stencil/aperture design.

Reference only; confirm against the official mechanical drawing before locking the footprint.

Wearables & Compact Consumer Devices

The 1.2×1.0mm footprint supports aggressive PCB miniaturization for smartwatches, trackers, earbuds, and other battery-powered devices where reference clock stability impacts link reliability and user experience.

• Smartwatches / fitness trackers
• Compact medical wearables
• Space-limited consumer electronics

Wireless Modules & IoT Nodes

Common reference clocking for Wi-Fi / Bluetooth / other RF modules, SoCs and connectivity chipsets where crystal tolerance and stability are mapped to frequency error budgets and channel accuracy.

• Wi-Fi / Bluetooth modules
• IoT sensors and gateways
• Smartphones and miniaturized embedded systems

Related pages: Quartz Crystal Resonators • What Are Timing Devices?

Selection Checklist

• Model: FCX-1S
• Frequency: ___ MHz (24–76.8MHz)
• Load Capacitance (CL): 6 / 10 / 18 pF (target)
• Tolerance: ±10 ppm (target)
• Temperature Range: −40~+85 / −40~+105 / −40~+125°C
• Annual Volume: ___ pcs
• Target Build Date: ___

Procurement-Friendly Part Description (Example)

Application engineering support: Share your target frequency, CL requirement, the IC vendor’s negative-resistance guideline, and your temperature grade. We can help validate start-up margin and recommend a best-fit configuration.