NFC reader IC selected for car door locking module

For contactless key applications, the Marquardt NFC module is mounted inside the door handle, and also in the car’s centre console (inside the cabin). In the door handle, the 13.56MHz module couples with any standard NFC card (tag) or tag emulator, such as a mobile phone, smart watch or tablet. The driver simply has to touch their device to the handle, and the system has an operating range of around 4cm.

On recognising the authorized tag’s identity, the module instructs an Electronic Control Unit (ECU) to unlock the car. A second module in the centre console must again perform contactless coupling with the driver’s tag before enabling the car to start. The Marquardt module will be used in next-gen production vehicles from one of Europe’s premium car makers. A pre-production demonstration was on show at the Mobile World Congress exhibition in February 2015.

In the door handle application, the NFC reader has to operate in conditions hostile to RF transmissions: the sheet metal of the car door acts as an unwanted antenna, deflecting much of the RF energy emitted by the reader. Marquardt’s design engineers found that the AS3914 offered far more predictable and reliable performance in these conditions than other NFC reader ICs did. This is because the AS3914 combines high RF output power of up to 1W, high sensitivity, and a unique Automatic Antenna Tuning (AAT) feature which compensates for attenuating and distorting effects, such as those caused by the metal surfaces in vehicles.

Using the AS3914, Marquardt is able to achieve a range from the door handle of 4cm in almost all operating conditions, even in car designs which have a chrome metal overlay on the plastic door handle. This range suits the application, since it avoids the need for the driver to precisely position the tag or tag emulator next to the handle, making it easy to use, while preventing the user from inadvertently unlocking the car when passing near the door at a range of more than 4cm.

An additional benefit of the AS3914 is its low power consumption. A low-power capacitive/inductive wake-up function continually scans for tags, and wakes up the high-power NFC transmitter when it detects that a tag has moved into range. This low-power wake-up feature draws just 5µA in capacitive mode when polling every 100ms.

The door handle and centre console applications are not the only uses for the Marquardt NFC module: it is also expected to be used in aftermarket ‘contactless key’ products designed to be mounted directly behind the windshield. Here too the module must operate in a metallic environment, calling for the optimised receiver sensitivity and high RF output power of the AS3914.

“The automotive environment is a difficult place for an NFC device to work in because of the large amount of metal in the surrounding environment,” said Rene Wutte, Senior Marketing Manager, ams. “To succeed in this application, Marquardt drew on the unique strengths of the AS3914. ams is delighted to have been able to support such a forwardthinking company in developing a wholly new product for the automotive market. Marquardt has opened up a path that many others in the automotive industry can now be expected to follow.”

In a statement, Marquardt added: “ams and its AS3914 have been a delight to work with from start to finish. Even with early prototypes, we were able to achieve far longer range with the AS3914 than with competing reader ICs, and that meant that our design team could get to market faster with a greater tolerance for the difficult operating conditions in which our module will be deployed.”

The AS3914 is sampling now and will be in volume production at the end of 2015. The AS3914 is a variant of the existing AS3911B, and is intended for use in automotive applications: the AS3914’s test coverage has been adapted to meet the requirements of automotive product manufacturers.