August 2015


World's smallest transponder coils for automotive electronics

Transponder coils are key components for comfort and safety in vehicles. Apart from their use in PEPS systems (passive entry passive start) they are used for contactless tire pressure monitoring and thus perform an important safety role, as well as extending the life of the tires.

TDK Corporation presents new EPCOS SMT transponder coils with extremely compact dimensions: Measuring just 4.5 mm x 3.2 mm x 3.2 mm, the TC1812 has an inductance of 2.38 mH and is designed for operation in the Z-axis.

The TC1210 coil is available with an inductance value of 1.08 mH or 1.34 mH, depending on type, and is suitable for operation in either the X- or Y-axis. Furthermore, both TC1210 versions are currently the smallest transponder coils in the world as they measure just 3.2 mm x 2.5 mm x 2.2 mm.

Due to the reduced dimensions, it has also been possible to reduce the mass of the components by about a third compared to the predecessor products. For example, the TC1210 (B82450A1084C000) weighs just 50 mg, while the TC1812 (B82451A2384D000) weighs only 120 mg, making them an excellent choice for tire pressure monitoring systems (TPMS). These applications demand especially robust, low-mass components due to the high acceleration forces that are encountered. The terminals of the windings are laser-welded and provide high mechanical stability.

The TC1210 coil has a high sensitivity of 3.1 mV/µT or 3.5 mV/µT, depending on the type, while the TC1812 coils offers a sensitivity of 7.6 mV/µT. All new transponder coils are designed for a center frequency of 125 kHz, comply with the AEC-Q200 standard and are RoHS-compatible.

Correct tire pressure prevents accidents and lessens the impact on the environment.

The tire pressure specified by the manufacturer is crucial to road safety. For this reason, a growing number of vehicles are being equipped with wireless tire pressure monitoring systems, which are already a legal requirement in some countries.

These systems require a transponder – often combined with the valve – being fitted to each tire to measure the pressure at regular intervals. As soon as this pressure exceeds a specified tolerance, a warning is transmitted wirelessly that gives an audible and visual indication of the critical situation to the driver. Transponder coils, together with a capacitor connected in parallel, form a resonant circuit. EPCOS SAW components are suitable as resonators for this purpose.

It is particularly critical if the tire pressure is below the specified pressure. The increased rolling resistance and friction caused by low pressure – particularly on long journeys at high speed – results in the tire overheating. Ultimately, this could lead to the sudden disintegration of the tire, usually involving detachment of the tread, and the consequent possibility of a serious accident. Excessively low tire pressure also has a negative ecological impact as the greater rolling resistance increases fuel consumption and wears down the tires prematurely, because only the outer edges of the tread are in firm contact with the road surface. In addition, low tire pressure compromises safety by adversely affecting the handling and stability of the vehicle, causing it to "wander." Excessively high pressure, on the other hand, can also cause premature tire wear, as in this case the middle of the tread does all the work.

Key data

Ordering code





Read more