When is it better to use an FCO CMOS oscillator instead of a discrete crystal?

Use an FCO CMOS oscillator when you want a plug-and-play clock source, prefer to avoid designing and tuning a discrete crystal oscillator circuit, or need a single footprint that supports multiple frequency options.

Which FCO parts are best for low-power designs?

Low-power PJ series devices such as FCO-2P-PJ, FCO-3P-PJ, FCO-5P-PJ, FCO-6P-PJ and FCO-7P-PJ are optimised for reduced supply current and are well suited to battery-powered or USB-powered equipment.

Can FCO oscillators replace both a crystal and the MCU internal oscillator?

Yes. An FCO oscillator outputs a CMOS clock that can drive an MCU, SoC or FPGA directly, removing the need for an on-chip crystal oscillator block for that particular clock domain.

Entry-Level CMOS XO Oscillator Family for Plug-and-Play System Clocks | FCO Series

FCO CMOS oscillators from FCom Fuji Crystal combine a quartz resonator and oscillator circuit in a single SMD package. They deliver plug-and-play CMOS clock outputs for consumer electronics, development boards and low-power devices, reducing design effort and simplifying PCB layouts compared to discrete crystal oscillators.

CMOS XO Plug-and-play clock Development boards Low-power options

Benefits of FCO oscillators in entry-level applications:

No need to design or tune discrete oscillator circuits around crystals.
Single footprint can support multiple programmed frequencies.
Standard 3.3 V or 5.0 V CMOS outputs compatible with most digital ICs.
Low-power PJ variants for battery-operated devices and handheld equipment.

FCom Fuji Crystal FCO CMOS oscillator family for plug-and-play system clocks

Key Features of the FCO Entry-Level CMOS Oscillator Family

Integrated crystal and oscillator driver in compact SMD packages.
Standard CMOS clock outputs at commonly used frequencies.
Operating voltages suitable for modern digital ICs.
Options from entry-level standard oscillators to low-power variants.
Ready-to-use timing solution for fast time-to-market projects.

Recommended FCO Series for Entry-Level System Clocks

The series below are representative of the FCO portfolio for consumer, embedded and low-power applications. For the exact frequency and voltage options, refer to each product page.

Series	Package	Output Type	Recommended Use	Product Details
FCO-1C / FCO-2C / FCO-3C / FCO-5C / FCO-6C / FCO-7C	Standard SMD sizes from 2.5 × 2.0 mm to 7.0 × 5.0 mm	CMOS	General-purpose system clocks for MCUs, SoCs, FPGAs and host interfaces on consumer and embedded boards.	FCO-1C FCO-2C FCO-3C FCO-5C FCO-6C FCO-7C
FCO-2P-PJ / FCO-3P-PJ / FCO-5P-PJ / FCO-6P-PJ / FCO-7P-PJ	SMD packages matching standard FCO footprints	Low-power CMOS	Battery- or USB-powered devices, handheld terminals, barcode scanners and portable instruments.	FCO-2P-PJ FCO-3P-PJ FCO-5P-PJ FCO-6P-PJ FCO-7P-PJ
FCO-2K / FCO-6K 32.768 kHz Low-Current XO	SMD	CMOS 32.768 kHz output	Low-frequency RTC or reference clock where a logic-level clock input is preferred over a discrete tuning-fork crystal.	FCO-2K FCO-6K

Typical Applications for Entry-Level FCO CMOS Oscillators

Development and Evaluation Boards

MCU, MPU and FPGA evaluation boards frequently use FCO oscillators to avoid the need for discrete crystal circuits and to simplify frequency changes between different board variants.

Consumer and Home Electronics

Devices such as smart displays, home gateways, networked audio systems and small appliances can adopt FCO oscillators as their primary system clock, shortening design cycles and easing EMC validation.

Battery-Powered and Portable Devices

Low-power PJ variants of FCO oscillators support handheld equipment, payment terminals, scanners and portable instruments where current consumption and board simplicity are both critical.

CMOS Oscillator Selection Guide for Entry-Level Designs

Select the required output frequency based on the processor, interface or subsystem that the oscillator will drive.
Choose the supply voltage and package type compatible with the target PCB and assembly processes.
For battery-powered or always-on designs, prioritise PJ low-power variants to minimise system current draw.
Route the oscillator output with short traces and avoid heavy capacitive loads or long stubs to maintain signal integrity.

FAQ – Entry-Level FCO CMOS Oscillator Family

Can I swap between different frequencies using the same FCO footprint?

Yes. One advantage of FCO oscillators is that a single footprint can support multiple frequency options. You can standardise on a package and voltage, then select different frequency codes for each product variant.

How do FCO oscillators compare to crystal plus buffer solutions?

FCO devices are factory-trimmed and tested timing components. They typically reduce design risk and validation time compared to discrete crystal plus buffer arrangements, at the cost of a slightly higher unit price and power consumption.

Can I use FCO oscillators together with higher-grade timing devices on the same board?

Absolutely. Many systems use FCO oscillators for general-purpose clocks while reserving TCXO, VCXO or OCXO devices for more demanding timing domains such as communication links or synchronisation subsystems.

Need a fast, low-risk way to add clocks to your design? Start with FCO CMOS oscillators for plug-and-play system clocks, then combine them with FCom crystals and SAW filters to build a complete timing and RF signal chain.