The ST25TA family gathers the proximity-type NFC chips from STMicroelectronics, designed for consumer electronics and smartphone-touch interaction: Bluetooth and Wi-Fi pairing with a single gesture, interactive posters, product information, connected objects. Compliant with the ISO/IEC 14443A standard and the NFC Forum Type 4 format, its six references range from 64 bytes to 8 kB of memory, delivered preformatted as an NDEF file and protectable with 128-bit passwords; the B references add the TruST25 digital signature, an event counter and, on some variants, a GPO output able to wake up a microcontroller. All of them can be read and written by the vast majority of recent NFC smartphones.
Information
| Manufacturer | STMicroelectronics |
| Family | ST25TA |
| References | ST25TA512B, ST25TA02KB, ST25TA02KB-D, ST25TA02KB-P, ST25TA16K and ST25TA64K |
| Standard | ISO/IEC 14443A (proximity cards) |
| Protocol | NFC Forum Type 4 commands (ISO/IEC 7816-4 APDU) |
| NFC Forum type | Type 4 Tag compatible |
| Operating frequency | 13.56 MHz |
| Data rate | 106 kbit/s |
| Unique identifier (UID) | 7 bytes, factory programmed |
| Tuning capacitance | 50 pF on the B references; 25 pF on the 16K and 64K |
| Operating distance | A few centimeters (up to 10 cm depending on the antenna) |
| Data retention | 200 years |
| Write endurance | 1,000,000 cycles |
| User memory | From 64 bytes to 8 kB depending on the reference |
The references of the family
The ST25TA family is built around the B generation, complemented by two high-density references inherited from the same line, with every reference sharing the same protocol and the same protected NDEF file:
| Reference | User memory | Highlights |
|---|---|---|
| ST25TA512B | 64 bytes | B generation: NDEF file, 128-bit passwords, TruST25, counter |
| ST25TA02KB | 256 bytes | Identical to the ST25TA512B, four times the memory |
| ST25TA02KB-D | 256 bytes | Open-drain GPO output (active low) to wake up a microcontroller |
| ST25TA02KB-P | 256 bytes | CMOS GPO output (active high), no external resistor |
| ST25TA16K | 2 kB | High density, without TruST25 or counter |
| ST25TA64K | 8 kB | The largest memory of the family |
Every reference is delivered preformatted as an NDEF file, ready to encode: the message represents a URL of around 50 characters on the ST25TA512B, around 240 on the 02KB, and several thousand characters on the 16K and 64K. The historical references without the B suffix (ST25TA512, ST25TA02K and their variants) have given way to the B generation.
Features & security
- Ready-to-use NDEF file: the memory is delivered preformatted as a Type 4 compliant NDEF file, alongside a read-only Capability Container and a system file: the tag can be encoded immediately, without any preparation.
- Two 128-bit passwords: the NDEF file can be protected with two distinct 128-bit passwords, one for reading, the other for writing; access can also be permanently locked, a state that even the passwords can no longer change. On delivery, the passwords are set to zero.
- TruST25 digital signature: the B references embed the STMicroelectronics digital signature, generated during production, which makes it possible to verify the authenticity of the silicon and detect clones.
- Event counter: a 20-bit counter, specific to the B references, tracks activity on the NDEF file.
- GPO output for embedded electronics: the ST25TA02KB-D and -P add a pin that signals RF activity and can wake up a microcontroller, open-drain (active low) on the -D, CMOS (active high, no external resistor) on the -P: the key to a Bluetooth or Wi-Fi pairing triggered with a single gesture.
- Small antennas and longevity: the 1.7 × 1.4 mm package and the 50 pF internal tuning of the B references allow tiny antennas, with 200-year data retention and one million write cycles.
The 16K and 64K, inherited from the same line, focus on capacity (25 pF tuning, without TruST25 or counter) and share the same NDEF file protection with 128-bit passwords.
Compatibility
The ST25TA chips use NFC-A technology (ISO/IEC 14443A), supported by the vast majority of recent NFC smartphones. On Android, reading and writing work natively with NFC Tools, without any particular restriction. On iPhone, automatic background reading is available from the iPhone XS and XR onwards; models from the iPhone 7 can read and write these chips via NFC Tools on iOS 15.6 or later, by starting the scan manually from the app.
With NFC Tools, the ST25TA chips support reading technical information, reading and writing NDEF records, erasing and protecting the file. The 128-bit passwords are managed through the chip's dedicated commands. The list of compatible models is available in the article on compatibility.
ST25TA vs ST25TV
| Family | Standard | Strengths | Positioning |
|---|---|---|---|
| ST25TA | ISO/IEC 14443A (proximity, Type 4) | 128-bit passwords, TruST25, GPO output | Pairing and consumer electronics |
| ST25TV | ISO/IEC 15693 (vicinity, Type 5) | Passwords, TruST25, kill and untraceable | Product protection and long-range logistics |
The two families split STMicroelectronics' two NFC standards between them: the ST25TA plays proximity (the quick exchange at smartphone touch, pairing, the GPO output to a microcontroller), the ST25TV plays vicinity (the long range of RFID readers, inventory, the kill and untraceable modes). On the NXP side, the NTAG213 remains the reference for consumer NFC tags.
Frequently asked questions
Which ST25TA reference should I choose?
For a short link, the ST25TA512B is enough; for common NDEF content (vCard, long URL, pairing), the ST25TA02KB is the natural choice; the -D and -P variants are the way to go as soon as a microcontroller must be woken up by the smartphone's tap; the 16K and 64K answer large data volumes.
What is the GPO output of the ST25TA02KB-D and -P for?
This pin signals RF activity to the surrounding electronics: it wakes up a microcontroller when the smartphone passes by, the starting point of a Bluetooth or Wi-Fi pairing. The -D version is open-drain (active low, with a pull-up resistor), the -P version is CMOS (active high, no external resistor).
Are the ST25TA chips compatible with iPhones?
Yes. Background reading works from the iPhone XS and XR onwards, and both reading and writing are possible via NFC Tools from the iPhone 7 on iOS 15.6 or later.
Can an ST25TA chip be protected against rewriting?
Yes: the NDEF file can require a 128-bit password for writing (a reversible protection), or be permanently locked as read-only, a definitive state that the passwords cannot reopen.
Useful links
