This is information on a product still in production but not recommended for new designs. For further information contact
your local STMicroelectronics sales office.
November 2016 DocID030000 Rev 1 1/3
ST25R3911
High performance HF reader / NFC initiator
with 1 W supporting VHBR and AAT
Data brief - not recommended for new design
Features
•ISO 18092 (NFCIP-1) Active P2P
•ISO14443A, ISO14443B and FeliCa™
•Supports VHBR (3.4 Mbit/s PICC to PCD
framing, 6.8 Mbit/s AFE and PCD to PICC
framing)
•Capacitive sensing - Wake-up
•Automatic antenna tuning system providing
tuning of antenna LC tank
•Automatic modulation index adjustment
•AM and PM (I/Q) demodulator channels with
automatic selection
•Up to 1 W in case of differential output
•User selectable and automatic gain control
•Transparent and Stream modes to implement
MIFARE™ Classic compliant or other custom
protocols
•Possibility of driving two antennas in single
ended mode
•Oscillator input capable of operating with
13.56 MHz or 27.12 MHz crystal with fast
start-up
•6 Mbit/s SPI with 96 bytes FIFO
•Wide supply voltage range from 2.4 V to 5.5 V
•Wide temperature range: -40 °C to 125 °C
•QFN32, 5 mm x 5 mm package
Description
The ST25R3911 is a highly integrated
HF reader / NFC initiator IC, including the analog
front end (AFE) and a highly integrated data
framing system for ISO 18092 (NFCIP-1) initiator,
ISO 18092 (NFCIP-1) active target, ISO 14443A
and B reader (including high bit rates) and
FeliCa™ reader. Implementation of other
standard and custom protocols like MIFARE™
Classic is possible using the AFE and
implementing framing in the external
microcontroller (Stream and Transparent modes).
The ST25R3911 is positioned perfectly for the
infrastructure side of the NFC system, where
users need optimal RF performance and flexibility
combined with low power.
Thanks to Automatic Antenna Tuning technology
the device is optimized for applications with
directly driven antennas. The ST25R3911 is alone
in the domain of HF reader ICs as it contains two
differential low impedance (1 Ohm) antenna
drivers.
The ST25R3911 includes several features that
make it very suited for low power applications. It
contains a low power capacitive sensor that can
be used to detect the presence of a card without
switching on the reader field. The presence of a
card can also be detected by performing a
measurement of amplitude or phase of signal on
antenna LC tank, and comparing it to the stored
reference. It also contains a low power RC
oscillator and wake-up timer that can be used to
wake up the system after a defined time period,
and to check for the presence of a tag using one
or more low power detection techniques
(capacitive, phase or amplitude).
The ST25R3911 is designed to operate from a
wide (2.4 V to 5.5 V) power supply range;
peripheral interface IO pins support power supply
range from 1.65 V to 5.5 V.