FAQ questions and answers

We are repeatedly asked the following question:

"What is the easiest SMD 32.768 kHz crystal to replace a THT TC38 (3x8mm) or THT TC26 (2x6mm) 32.768 kHz crystal with?"

Quite simply, with our cheapest 32.768 kHz crystal from the M3215RR series in a 3.2x1.5mm/2pad ceramic housing.

Why?

THT crystals have lower resistances than MINI-SMD-32.768kHz crystals due to their large tuning fork resonators. Normally 50 kOhm max.

So if the same IC is to be operated with an SMD 32.768 kHz crystal instead of the THT clock crystal, then the maximum resistance of the SMD crystal must not exceed 50 kOhm, otherwise massive oscillation problems may occur. This means that 32,768 kHz crystals in even smaller housings with the dimensions 2.0x1.2mm or 1.6x1.2mm can be ruled out, as these have a significantly higher resistance of 90kOhm.

The 3.2x1.5mm/2pad SMD crystals of the M3215RR series feature our highly innovative LRT (LOW ESR Resonator Design) quartz resonators with a maximum resistance of 50 kOhm. Each of our products is 100% tested, so we can offer outstanding product quality, maximum lifetime and a very reliable partnership with competent support. Based on our own mold, we can also supply the SMD clock crystals of the M3215RR series at very competitive prices.

If you compare the price of the M3215RR to the price of a THT-32.768kHz crystal, then the M3215RR is by far the cheaper solution.

THT-32.768kHz crystals also have glass feedthroughs surrounding the contact terminals, which must be taken care of when handling THT-32.768kHz crystals to avoid damage and failure. The M3215RR, on the other hand, is a perfectly processable SMD component.

We therefore recommend the LOW ESR 50 kOhm max. 32.768kHz SMD crystals in the 3.2x1.5mm/2pad of the M3215RR series to our customers.

M3215RR 32.768 kHz crystals are available with load capacities of 4, 6, 7, 9 or 12.5 pF. Normally from stock.

Link to the product configurator M3215RR

PETERMANN-TECHNIK GmbH is the right partner if you are looking for an inexpensive SMD clock crystal but do not want to compromise on quality, transient response reliability and series availability. Our 32,768 kHz SMD clock crystal from the M3215RR series in a 3.2x1.5 mm/2 pad ceramic housing combines an attractive price with a technically strong LOW-ESR resonator design.

Especially with 32,768 kHz clock crystals, the cheapest crystal is not automatically the best choice. The decisive factor is whether the crystal oscillates safely in the respective oscillator circuit, works reliably and remains available in the long term. Smaller 32.768 kHz SMD crystals can have a higher resistance and therefore lead to oscillation problems in certain circuits. With its 50 kOhm LOW ESR design, the M3215RR offers a very good combination of economy, functional reliability and practicality.

PETERMANN-TECHNIK therefore recommends solutions that are technically sensible, attractively priced and suitable for long-term use. Customers benefit from 100% tested quality, expert advice, fast sample availability and a solution that is suitable for reliable real-time clock, IoT, smart meter, industrial and automotive applications.

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