Practically every electronic device has some kind of crystal resonator that sets the frequency of operation. Multiple crystals are also common. These frequency-determining devices have almost always been large devices, often with metal packages. But thanks to some amazing technological and packaging developments, crystals are shrinking along with the circuits they trigger.

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The ST3215SB surface-mount crystal resonator from AVX Corp. targets consumer and mobile equipment (Fig. 1). Operating at the standard frequency of 32.768 kHz, it comes in a miniature ceramic package that measures 3.2 by 1.5 by 0.8 mm. Its frequency tolerance is ±20 ppm with a maximum equivalent series resistance (ESR) of 70k. Also, it operates from –40°C to 85°C. Standard capacitance ranges are 9 to 12.5 pF. Versions with capacitance of less than 7 pF are available on request. The lead-free part complies with the European Union’s Restrictions on Hazardous Substances (RoHS) as well.

Figure 1. The AVX ST3215SB is a 32.768-kHz tuning fork crystal resonator that’s 3.2 by 1.5 by 0.8 mm.

The Micro Crystal CC7A-T1A measures just 3.2 by 1.5 by 0.90 mm (Fig. 2). This AT-cut crystal offers a wide temperature range from –40°C to either 85°C or 125°C with a thermal stability down to ±10 ppm. It’s available in the frequency range of 30 to 500 kHz with a standard 32.768-kHz unit available. Other standard frequencies available include 24, 26, and 26.5 MHz or any custom frequency in the 24- to 30-MHz range. Lead-free, it complies with RoHS as well. Target applications include medical and medical telemetry for implantable devices.

With dimensions of 1.55 by 0.95 by 0.35 mm, the CX18 surface-mount quartz crystal oscillator from Statek Corp. may be the smallest crystal oscillator available. Its frequency range is above 30 MHz, and its calibration tolerances are in the range of 5 ppm. 50-MHz samples of the product are available now. Potential applications include medical, military, industrial, and smart-card products.

Figure 2. The Micro Crystal CC7A-T1A crystal is designed for applications in the 30- to 500-kHz range with a standard version for 32.768 kHz available. Measuring 3.2 by 1.5 by 0.9 mm, it targets medical and implantable devices.

AVX Corp.

Micro Crystal

Statek Corp.