Smart locking systems are increasingly replacing traditional locks. For these innovative lock models, Infineon’s NAC1080 fits like a key in a lock, as it combines NFC, motor control, and energy harvesting in one chip. This eliminates the need for an additional power source, which obviously reduces costs.
An electromechanical lock is called “smart” if it can be opened and closed by wireless communication with an electronic key. Mobile devices, such as smartphones, wearables, and other tokens, assume the role of a traditional key. Communication between the key and the lock is usually via Bluetooth, WiFi, or near-field communication (NFC).
These smart locks allow secure and convenient access control by making physical keys a thing of the past. New keys can also be conveniently managed, which is a big advantage in buildings with multiple locks. This is one of the reasons why smart locks are a rapidly growing segment in the IoT sector. For example, the market research and consulting firm Grand View Research put the global market at US$ 1.95 billion in 2022. It is expected to grow at a compound annual growth rate (CAGR) of 19.6 percent between 2023 and 2030, driven by a growing adoption of advanced communication technologies, convenience, and increased interest in advanced security systems.
Structure and function of smart locks
Smart locks essentially consist of a traditional mechanical lock and an electronic control unit. A microcontroller authenticates the user through a digital key exchange (e.g. via NFC) and passes the subsequently sent control commands to the motor drivers to lock or unlock a lock.
Previous applications with an electrical power source operate as active participants in NFC communication. As a result, the motors that control the mechanical part of the lock are also supplied with electricity by this power source.
With the NAC1080, no addiotnal power source is needed
A smart lock based on Infineon’s NAC1080 NFC controller, which acts as a passive NFC participant, uses the voltage induced by the active NFC participant for communication and to power the application, including the motor. With this energy (which is temporarily stored in the capacitor) and an integrated H-bridge driver, the NAC1080 can drive small motors in the milliwatt range (up to 250 mA load current). The combination of passive NFC operation and a double-layer capacitor eliminates the need for an additional power source, such as batteries or accumulators, thereby reducing costs. The actual charging process takes only a few seconds and does not require an additional battery management system.
When the NAC1080 is accessed by the user, the AES128 symmetric encryption method with a random number generator provides the required security. A universal asynchronous receiver/transmitter (UART) or serial peripheral interface (SPI) can be used to read documented log files. This makes it possible to assign the operation of the hardware to the users at any time.
The NAC1080 is based on a programmable 32-bit Arm Cortex M0 core operating at a CPU frequency of 28 MHz. It is available in DSO-16 (4 mm × 10 mm) and VQFN32 (5 mm × 5 mm) packages. An evaluation kit, included software libraries, and a cell phone app enable developers to carry out quick commissioning.
With this single-chip solution, compact locks that require only a low level of torque can be developed easily and cost effectively. Examples include office cabinets, bicycle locks, and mailboxes. They can be opened within a few seconds. Depending on the components and smartphone used, opening time can vary. In addition, other applications are also possible, such as sensors that are not directly accessible for tire pressure testing.
Operation and communication during a power failure
If the NAC1080 is integrated into larger locking systems and used as a passive component, it can continue to be used despite a power failure, empty batteries in the smart lock, or loss of keys. In this scenario, the IC also powers the door lock directly via the NFC interface.
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