How Quartz Is Used in Electronics: From Watch Crystals to 5G

Q: Why choose quartz over MEMS for timing?

Quartz still leads in phase noise, aging, and ultra‑low jitter across many frequencies, making it ideal for RF, high‑speed serial, and precision measurement. MEMS excels in shock robustness and integration—choose by system priorities.

Q: What’s the best frequency for an MCU clock?

Choose a frequency aligned to your MCU, toolchain, and peripheral requirements (e.g., 8/12/16/24/25/48 MHz). For RTC only, 32.768 kHz tuning‑fork crystals are ideal.

Q: How do ppm and time error relate?

1 ppm ≈ 1 microsecond per second ≈ 86.4 milliseconds per day. A ±2 ppm TCXO drifts about ±0.17 seconds per day—okay for GNSS‑assisted systems but not for long holdover without correction.

Q: When should I move from XO to TCXO or OCXO?

Indoor devices with stable temps and tight budgets can use XO. Outdoor or RF/link‑sensitive designs benefit from TCXO. Carrier‑grade timing and precision measurement often require OCXO with ppb‑class stability and very low phase noise.

Updated Oct 17, 2025 · 8–10 min read · Topic: quartz electronics

By FCom Editorial Team · Reviewed by Technical Marketing

Why quartz?
Device families
Where you’ll meet quartz
Choosing the right solution
Key specs that matter
Practical design checklist
Quartz at FCom
FAQ

If electricity is the blood of a circuit, quartz is often its heartbeat. Under the umbrella of quartz electronics, a thin slice of crystalline SiO₂ quietly sets the pace for microcontrollers, radios, networks, storage, and test instruments. This article explains how quartz works, which device families you’ll meet in real designs, where they’re used, and how to choose the right part—plus practical layout tips to make your timing rock‑solid.

Why quartz?

Quartz is piezoelectric: apply a voltage and it deforms; strain it and you get a voltage. Cut a wafer at the right angle and thickness, and it resonates at a highly stable natural frequency. Because quartz is crystalline and the cut angle is controllable (AT‑cut, SC‑cut, etc.), its temperature behavior, aging, and Q factor can be engineered—delivering ppm‑class accuracy and exceptionally low phase noise compared with many ceramic or MEMS alternatives.

Block diagram: quartz resonator in an amplifier feedback loop (quartz electronics)

The building blocks of quartz electronics

1) Crystal Resonators (2‑pin “bare” quartz)

Provide a frequency‑selective element inside an IC’s oscillator loop (e.g., MCU XTAL pins).
Typical examples: 32.768 kHz tuning‑fork crystals for real‑time clocks; MHz‑range AT‑cut units for MCUs and radios.
Key parameters: load capacitance (CL), ESR, drive level, aging, tolerance/stability.

2) Crystal Oscillators (XO / TCXO / VCXO / OCXO)

Quartz + amplifier + control network + buffer—direct clock output.
XO: cost‑efficient, general‑purpose stability.
TCXO: temperature‑compensated, typically ±0.5–±2 ppm; ideal for GNSS, cellular, IoT.
VCXO: voltage‑tunable for PLL/clock alignment and jitter control.
OCXO: oven‑controlled for ppb‑class stability and very low phase noise; used in test, base stations, boundary clocks.
Watch for: tolerance/stability, phase noise/jitter, VDD, output format (CMOS/Clipped Sine/LVDS/HCSL), start‑up, temp range, package, aging.

3) SAW/BAW Devices

SAW (surface acoustic wave) resonators/filters often use quartz substrates.
Applications: Wi‑Fi, Bluetooth, NFC, automotive key fobs, IF filtering.
Key specs: center frequency, bandwidth, insertion loss, selectivity, temperature drift, power handling.

4) Quartz‑based Sensors

Use piezoelectric and resonant effects for high‑sensitivity measurements.
Found in industrial and lab instruments where drift and noise matter.

Where you’ll meet quartz

Consumer & IoT
MCU system clocks, 32.768 kHz RTCs, Bluetooth/Wi‑Fi/GNSS timing, wearables, cameras.

Computing & Storage
Reference clocks for PCIe, USB, SATA, Ethernet PHYs; jitter budgets for SERDES.

5G/Telecom & Networking
OLT/ONU, RRU, small cells, switches/routers; TCXO/OCXO and VCXO for sync.

Automotive & ADAS
Domain controllers, cameras, radar/LiDAR, in‑vehicle Ethernet.

Industrial & Energy
PLC/DCS, smart meters, edge gateways; temperature, vibration, and aging robustness.

Medical & Test
Ultrasound, imaging subsystems, spectrum/time‑base in precision instruments.

Choosing the right quartz solution

Simple, low‑power MCU clock? Use a crystal resonator or low‑power XO. Match CL/ESR to MCU datasheet; ensure start‑up margin.
Battery devices outdoors (GNSS, cellular, trackers)? Use a TCXO (±0.5–±2 ppm across −40 to +85/105 °C) to shorten TTFF and stabilize links.
Need frequency trim in a PLL or network alignment? Choose a VCXO with suitable pull range (ppm) and control linearity.
Carrier‑grade timing/holdover and ultra‑low phase noise? Choose an OCXO (ppb‑class); account for warm‑up power and ventilation.
RF filtering around IF/RF bands? Consider SAW filters/resonators; evaluate insertion loss and temperature coefficient.

Key specs that matter

Frequency tolerance vs. stability: factory tolerance vs. drift across temperature/time.
Phase noise & jitter: critical to SERDES, RF, ADC/DAC performance.
Aging: often a few ppm in year one, decreasing thereafter—budget for long‑term accuracy.
Temperature range: industrial (−40~+85 °C) and wide temp (+105 °C+); consider thermal shock and package stress.
Power & start‑up: battery devices prefer mW‑class clocks; OCXOs require warm‑up energy/time.
Output format/swing: match CMOS/Clipped Sine/LVDS/HCSL, rise/fall, and load.

Practical design checklist

For crystal resonators (MCU)

Use MCU‑recommended CL and external caps; account for trace parasitics and adjust if needed.
Keep‑out: short traces, solid ground reference; avoid crossings by high‑di/dt nets and switchers.
Drive level: avoid over‑drive to reduce aging; a series resistor can tame loop gain and start‑up stress.

For oscillators (XO/TCXO/VCXO/OCXO)

Decoupling: place 0.1 µF + 1 µF at VDD; consider LC filtering for noisy rails.
Output termination: match to line impedance; prefer differential for long/high‑speed runs.
Enable/Standby: use OE/Standby pins for power and start‑up sequencing.
Thermal: keep TCXO/OCXO away from heat; allocate warm‑up time and airflow for OCXO.

Quartz at FCom Fuji Crystal

FCom Fuji Crystal offers a complete portfolio of crystal oscillators (XO/TCXO/OCXO/VCXO) and timing devices for wearables, GNSS modules, networking, and measurement equipment.

FAQ

Why choose quartz over MEMS for timing?

Quartz leads in phase noise, aging, and ultra‑low jitter at many frequencies, making it ideal for RF, high‑speed serial, and precision measurement. MEMS excels in shock robustness and integration—choose by system priorities.

Are SAW filters part of “quartz electronics”?

Yes. Many SAW devices use quartz or other piezo materials to implement RF filtering and resonators. They complement timing oscillators by shaping RF spectra rather than providing a digital clock.

What’s the best frequency for an MCU clock?

Pick a frequency favored by your MCU and toolchain (e.g., 8/12/16/24/25/48 MHz). If you only need RTC, 32.768 kHz tuning‑fork crystals are ideal.

How do ppm and time error relate?

1 ppm ≈ 1 µs/second ≈ 86.4 ms/day. A ±2 ppm TCXO drifts ~±0.17 s/day—fine for GNSS‑assisted systems but not for long holdover without correction.

When should I move from XO to TCXO or OCXO?

Indoor, stable‑temp, cost‑sensitive designs → XO. All‑temperature or RF/link‑sensitive → TCXO. Carrier‑grade timing/measurement → OCXO (ppb‑class), with warm‑up and thermal planning.

Fuji Crystal

How Quartz Is Used in Electronics: From Watch Crystals to 5G

How Quartz Is Used in Electronics: From Watch Crystals to 5G

Contents

Why quartz?

The building blocks of quartz electronics

1) Crystal Resonators (2‑pin “bare” quartz)

2) Crystal Oscillators (XO / TCXO / VCXO / OCXO)

3) SAW/BAW Devices

4) Quartz‑based Sensors

Where you’ll meet quartz

Choosing the right quartz solution

Key specs that matter

Practical design checklist

For crystal resonators (MCU)

For oscillators (XO/TCXO/VCXO/OCXO)

Quartz at FCom Fuji Crystal

FAQ

Further reading

References