ST Introduces Minuscule NFC Reader for Embedded Contactless Interaction

April 17, 2024 by Duane Benson

At Embedded World 2024, STMicroelectronics showed off a 4 mm x 4 mm NFC reader that balances performance, cost, and power consumption.

STMicroelectronics introduced the latest in its near-field communication (NFC) reader product line. The ST25R100 is designed to up the contactless card performance-per-watt game in its entry-level NFC product family. With dual-antenna support, solid wake-up range, and standby power drain as low as 1µA, the ST25R100 may be useful for space- and power-constrained applications.


ST's NFC reader

STMicroelectronics’ new ST25R100 entry-level NFC chip. Image (modified) used courtesy of STMicroelectronics

Improving Entry-Level NFC Performance

ST says that the entry-level ST25R100 offers high RF performance, even with low power and small antennas. It reportedly has better wake-up performance, low-power card detection, and dynamic power output to keep within certification specifications. 

The new chip (datasheet linked) reads and writes at 0.5 W and uses an advanced analog front end (AFE) and integrated data framing system to support NFC-A/B (ISO 14443A/B, up to 106 kb/s) and NFC-V (ISO 15693, up to 53 kbit/s) protocols. It can be configured for custom protocols while in reader mode. It has an improved wake-up range, low power consumption, and small package size, making it attractive for small battery-powered devices.


STMicroelectronics’ Marian Langsfeld

STMicroelectronics’ Marian Langsfeld demonstrating the new ST25R100 at Embedded World 2024 in Nuremberg, Germany.

NFC standards have maximum and minimum power limits. The ST25R100 can adjust output power to stay under the maximum limits. While most NFC readers limit their overall power output to prevent exceeding the power limits, doing so limits range. The ST25R100 includes a dynamic output power system to prevent overpower without losing detection range.


Getting the Wake-Up Call in Time

One of the most critical factors in NFC devices is the wake-up performance. An NFC reader must have a low standby current draw and wake up in time to perform its communications duties.

The new ST part can sleep at 1 µA and still detect cards soon enough to start communicating on time. It delivers improved wake-up performance over previous offerings with version two of ST’s NFC inductive wake-up scheme. The chip can be configured to automatically ping (call to nearby cards) at intervals from 10 to 1,700 ms. It can average responses out over 4, 8, 16, or 32 cycles and can be set to trigger upon card approach, card removal, or both.


ST25R100 key features

ST25R100 key features. Image used courtesy of STMicroelectronics

The chip’s maximum wake-up range for NFC devices utilizing ISO 14443A, ISO 14443AB, and ISO 15693 protocols is significantly greater than the previous generation of ST25R NFC readers at 125 mm,105 mm, and 145 mm (4.8”, 4.1”, and 6.1”), respectively. It contains enhanced low-power card detection (LPCD), improving its ability to detect cards with small antennas.


Keeping the Footprint and Power Budget Small

The 4 mm x 4 mm TQFN-packaged part is designed for small, low-power devices. It communicates with a host microcontroller over a 6 Mb/s SPI bus plus an IRQ line. It’s compatible with supply and peripheral voltages from 2.7 V to 5.5 V. The chip uses two oscillators. It has a 27.12 MHz crystal oscillator with an external crystal for power up and an internal RC oscillator for standby mode to reduce power drain.


NFC Everywhere

ST designed the ST25R100 specifically for consumer and industrial NFC applications. By leaving out some high-end features, ST optimized the part for entry-level installations without the compromises that would have come with making it a broad-application part. Key design factors broaden this device's application potential, including small component packaging, optimized interaction range, longer battery life, and compatibility with industry standards.

The ST25R100 NFC reader specifically targets printers, power tools, gaming terminals, home appliances, medical devices, and access controls. Space-constrained NFC devices benefit from the new part's small chip size, low power draw, and high performance per watt.