ST Dynamic NFC/RFID tags with I2C and 13.56 MHz RF interfaces


Amit Sethi
, Technical Marketing Manager, MDG Group, STMicroelectronics, India

ST’s Dynamic NFC/RFID Tags which is a part of the ST25 family, features an EEPROM memory that can be accessed either by the I2C interface or by the RF (ISO15693/ISO14443) interface operating at 13.56 MHz frequency. As compared with the NFC tags, which only stores static data, ST Dynamic tags can exchange data with MCU dynamically with I2C interface and send the ‘dynamic’ data to NFC compatible smartphones, which allows users to exchange data and track their system dynamically. Dynamic Tags comes into 2 series, M24LR (ISO15693) and M24SR (ISO14443).

These devices are based on the passive RF technology, so no power is needed to operate these devices in the RF mode. Users just need to add a 13.56 MHz inductive antenna onto a PCB, to access the RF feature of this device. This provides the flexibility to remotely program or to update the electronic products, anytime during their lifetime, anywhere in the supply chain. This also allows the manufacturers to update parameters, update software without connecting a programmer, or even disassembling the encapsulating container. Thus enabling the user to add new features, reduce manufacturing cost and inventory management.

The energy harvesting function of M24LR allows the surplus energy from an RF signal to be used by the application, enabling battery-less designs. M24LR has a Vout pin which can provide energy to supply a low power micro-controller, a low power LCD or other components for an application like LED. This function can enable battery-less applications such as e-paper based electronic shelf labels, which you can update the display using purely the energy harvested by M24LR.

Security is always a major concern, especially in wireless applications. Both M24SR and M24LR are embedded with the 128-bit and 32-bit password respectively, which protect the read or write access from RF or I²C interface and protects the application from tampering and unexpected access to memory. This gives a new perspective for the data management. Users can safeguard the critical information like the traceability information, identification data, user settings and the event log management. Also, it comes with a 64-bit unique identifier (UID), which can be used for security functions.

It also features an RF disable input and a digital status output pin allowing flexibility for applications such as MCU wake-up. The M24SR and M24LR series are available in high-reliable EEPROM memory (one million erase/ write cycles and 200 years’ data retention) densities from 2 Kbit to 64 Kbit and three package types: SO8, TSSOP8, and UFDFPN8.

The ability to read and write parameters from inside (I2C) and outside (RF) makes these dynamic tags suitable for the wide range of applications like:

  • Medical Equipment
  • Industrial Equipment
  • Factory and Building Automation
  • Computers and Peripherals
  • Consumer Electronics

STMicroelectronics offers a number of development tools to help in designing the applications using M24LR and M24SR devices. These tools include reference boards, antenna evaluation board, demonstration kits and evaluation boards. These tools can be used to test features like password protection, operating distance from the device and impact of the size of an antenna on the application. The available reference kits are:

  • M24SR-DISCO-PREM (NFC/RFID tag, STM32F1 MCU, color display, Bluetooth/audio module)
  • X-NUCLEO-NFC01A1 (Dynamic NFC tag expansion shield based on M24SR for STM32 Nucleo)
  • M24LR-DISCOVERY (Discovery kit for M24LR04E dynamic NFC/RFID tags with energy harvesting)

The Dynamic tags family offers a simple and cost-effective implementation. ST can provide supporting material for integrating the antenna into your application: application notes, reference designs, antenna computation tools, e-presentations and e-learning. Visit