NFC Controller

What Is an NFC Controller?

An NFC controller is a dedicated integrated circuit installed in smartphones, payment terminals, and other active NFC devices that manages the complete NFC protocol stack. Unlike a passive tag chip that only responds to external fields, the NFC controller actively generates the 13.56 MHz RF field, handles signal modulation and demodulation, manages protocol timing, and interfaces with the host processor.

Role in the NFC System

The controller sits between the NFC antenna and the host processor:

• RF field generation: Driving the antenna at 13.56 MHz to energize passive tags.
• Modulation/demodulation: Encoding data using ASK modulation and Modified Miller coding; decoding load modulation from tags.
• Protocol handling: Managing anti-collision sequences and ISO 14443 / ISO 15693 state machines.
• Mode management: Switching between reader/writer, card emulation, and peer-to-peer modes.

Major NFC Controllers

NCI (NFC Controller Interface)

Modern controllers implement the NFC Forum's NCI specification, a standardized command interface between controller and host processor. NCI abstracts hardware differences, allowing the same driver to work with different controller chips. It defines commands for RF discovery, data exchange, mode selection, and power management.

NFC Controller vs NFC Chip

Integration in Smartphones

The NFC controller is typically connected to the application processor via I2C or SPI. Apple uses a custom controller integrated with their secure enclave. Android devices commonly use NXP PN-series controllers with Google's NFC stack handling NDEF dispatch and HCE.