ST’s NFC Tag Type 2 ICs Boasts Energy Harvesting, Privacy, and Increased Protection

November 14, 2021 by Abdulwaliy Oyekunle

STMicroelectronics aims to guarantees privacy in common near-field communication (NFC) applications such as contactless transactions, healthcare records, seamless access to digital content with new NFC tag ICs.

The near-field communication technology, like NFC tags (like an RFID tag), which stores user information, often facilitates two-way wireless communication between NFC-enabled devices. With inductive coupling between the NFC-enabled devices, near-field communication occurs in short-range at a frequency of 13.56 megahertz. 

One major advantage of short-range transmission in near-field communication technology is that less power is consumed during operation.

Hoping to capitalize on the advantages of NFC, STMicroelectronics (ST) has announced its ST25TN family of NFC Forum Type 2 tags, which comprises two IC-based devices: ST25TN512 and ST25TN01K.


A representation of ST's latest NFC tag ICs

A representation of ST's latest NFC tag ICs. Image used courtesy of STMicroelectronics


This article will take a look at NFC tag features, namely the types of tags, and then dive into the characteristics of STs NFC ICs. 


Features of NFC Tags

In general, NFC tags are distinguished by the type of standard they are based on and their capabilities, including memory, data transfer rate, etc. Additionally, tag types are standardized by the NFC Forum, among other standardization bodies such as GlobalPlatform, to ensure interoperability between NFC-enabled devices in the market. 

All in all, there are four tag types numbered from one to four, in addition to a fifth tag which is based on NFC-V technology. 


A chart with NFC Forum tag types.

A chart with NFC Forum tag types. Image used courtesy of Maka RFID


While NFC tag Type 1 and Type 2 are based on ISO/IEC 14443A standard, the NFC tag Type 3 is based on the JIS X 6319-4 (or FeliCa). 

Thanks to a high connection speed of 424 kbps, NFC tags Type 3 and 4 can be employed in applications such as transit tickets and membership cards.

When it comes to ST's new tag ICs, they are Type 2; thus, they can have expandable memory from 48 bytes to 208 bytes. NFC Type 4 tags, however, features memory capability of up to 32 Kbytes to store user contents.

Even though NFC tag Type 1 supports read and re-write operations by default, users can configure the tag to support read-only operations. This tag type also finds applications in Bluetooth devices.

Now that the general basics of NFC types and basic features are understood let's look at ST's tag ICs a bit closer.


Energy Harvesting, Power Transfer, and Protection

One key feature of the ST25TN series of NFC tags is how they support energy harvesting, which, depending on the application, is an important feature to support. Energy harvesting involves transforming the inducted energy into an electrical current as low as 3 mA to supply the tag.

With inductive coupling, an electromagnetic field at 13.56 megahertz is generated by an active NFC-enabled transmitter device, and the NFC tag utilizes this as a form of power supply. This way of energy harvesting eliminates the need for an internal power supply such as a battery and battery compartment.


Functional diagram of the ST25TN family of NFC tag IC.

Functional diagram of the ST25TN family of NFC tag IC. Screenshot used courtesy of STMicroelectronics [downloadable datasheet]


Along with its energy harvesting feature, the IC tag includes inductive power transfer technology such as wireless power chargers. 

However, when the tag is adopted in this use case, a transmitting power value that exceeds the recommended specification could damage the tag. To protect the tag, designers should place a capacitor in series between the tag antenna and tag IC.

A final feature of this device is its privacy and protection mechanisms. Users can ascertain the authenticity of the device via the TruST25 digital signature feature. In addition, the device also features a 7-bit unique chip-identifier code as well as a 3-digit unique tap code.

The "kill" feature puts the device in "killed mode." In this mode, the device does not respond to incoming RF commands.

All in all, with a connection speed of up to 106 kbps, the new ST25TN family of NFC tag IC is a robust NFC-enabled device.  This device could facilitate seamless wireless communication with a single touch in various applications such as healthcare, consumer packaged goods, and e-tickets.