Crystal oscillators

A crystal and a crystal oscillator are two different components, and purchasing teams get them confused more often than engineers would like. Haiben is an electronic components supplier based in Shenzhen, founded in 2013, and stocked crystal oscillators sit in our published full range alongside our own-brand Weforsemi semiconductor line, operated by our wholly-owned subsidiary. This page separates the device families, lists the parameters engineers should put on a purchase order, and explains how to order from the Weforsemi crystals range.

Crystals and crystal oscillators: the distinction

A quartz crystal is a passive resonator. On its own it does nothing until a circuit drives it — usually an on-chip oscillator amplifier inside an MCU, SoC or clock IC. The crystal provides the frequency reference; the active circuitry around it does the oscillation. A crystal oscillator (often written XO) is a packaged module: a resonator plus an oscillator circuit in one package, with a supply pin and a clock output. You give it VCC and ground, and it produces a square wave.

That difference decides where the parts land in a bill of materials. If the MCU datasheet shows a crystal between two pins with load capacitors, you are buying a passive crystal. If the board needs a clock at a chip's input that has no oscillator of its own, you are buying an oscillator module. Designing the passive side involves load capacitance and drive level; designing with a module involves supply voltage, output logic and enable pin behaviour. Our article on crystal oscillator circuits covers the passive circuit in more detail, and is worth passing to new hardware engineers.

Specifying a crystal: frequency, load, tolerance

Three parameters separate one crystal from another, and a purchase order needs all of them.

• Frequency — the nominal value, usually stated in MHz or in kHz for low-speed parts. It must be one the resonator is cut for; you cannot substitute 16 MHz for 12 MHz in a timing-critical design.
• Load capacitance (CL) — the capacitance the crystal expects to see across its terminals. It is usually a single-digit to low-double-digit picofarad value, and the two external capacitors are selected against it. A crystal specified for one CL value in a circuit tuned for another pulls the frequency off. This is the most common specification error we see on customer BOMs.
• Tolerance and stability in ppm — a buyer-defined requirement. Tolerance covers the initial frequency error at 25 °C; stability covers drift over temperature, plus aging over time. Tightening either number narrows the part range and affects the achievable cost, so state the requirement rather than defaulting to the tightest figure.

Beyond the three basics, add operating temperature range, package outline and — where the MCU datasheet requires it — maximum drive level or ESR. For boards that pair timing with storage, it helps to source related devices together; our serial flash memory page covers non-volatile storage options, and power management ICs covers the rails an oscillator or clock IC will sit on.

SMD crystals and common frequency points

Surface-mount crystals in ceramic packages have largely displaced through-hole cylinders in new designs. SMD packages suit reflow assembly and automated placement, and they occupy less board area — relevant when a microcontroller design has one resonator and little space to give it. Specify the package outline and pad footprint from the manufacturer's drawing, and confirm it against your PCB land pattern before release.

Some frequency points recur so often in designs that buyers ask for them by habit. Among MHz-range values, 8, 12, 16, 24, 25 and 40 MHz are commonly specified, and 32.768 kHz appears wherever a real-time clock divides down to one second. Treat these as values to confirm against your schematic rather than as a stocked list: the right part is the one on your BOM, and an alternative frequency is not interchangeable in a timing path. When you enquire, give the frequency, the load capacitance, the ppm requirement and the package — that is enough for us to quote accurately.

Ordering from the Weforsemi crystals range

Crystal oscillators appear in our stocked full range, and crystals are part of the Weforsemi line. We do not publish model-level crystal data here, so treat any enquiry as a specification request: send the parameters above and our team will confirm what can be supplied and at what lead time. For mixed BOMs, crystals can be sourced alongside our other stock — for example the BL25Q128G, a 128 Mbit serial (SPI) NOR flash memory IC in an SOP-8 208 mil package with an operating voltage of 2.3 V to 3.6 V, from the manufacturer's published listing data.

PCBA customers can route the same requirement through our published workflow: Customer Design, BOM Analysis, Component Sourcing, PCBA Manufacturing (PCB fabrication, SMT, DIP, programming), Testing (in-house testing and global quality verification), Finished Product (assembly, packaging, customised solutions), then Delivery with on-time delivery and global logistics support. Our PCB & PCBA Solutions line covers custom PCB design, PCBA manufacturing and module assembly for prototypes, small batches and volume production. In all cases the website is operated by Haiben, the parent company; the Weforsemi line is produced by our wholly-owned subsidiary.

Frequently asked questions

Can you supply a crystal and an oscillator from the same source?

Crystal oscillators are listed in our stocked full range and crystals are part of the Weforsemi line, so both can appear on one enquiry. Send the specification for each line item and we will confirm availability separately, since the two device types have different parameters to match.

My BOM gives only a frequency. Is that enough to order?

Not usually. Frequency alone does not define a crystal: load capacitance, tolerance and stability requirements, operating temperature range and package outline all affect which part is correct, and load capacitance in particular must match the circuit's capacitor selection. Ask the design engineer to complete the specification before ordering.

What if a required frequency is not in your stocked range?

Enquiries are handled as specification requests. Provide the full requirement and our team will confirm what can be supplied and the lead time. For PCBA projects, the same requirement can be handled within the Component Sourcing step of our published workflow.