ST ST25R3911B User manual

December 2017 DocID029132 Rev 3 1/25
1
UM2042
User manual
Discovery kit for the ST25R3911B
high performance HF reader / NFC initiator
Introduction
The ST25R3911B-DISCO is a ready-to-use development kit to evaluate the functions of the
high performance HF reader / NFC initiator ST25R3911B in Reader mode for contactless
applications.
The ST25R3911B-DISCO kit supports
•ISO 18092 (NFCIP-1) active P2P
•ISO 14443A and ISO14443B
•ISO 15693
•FeliCa™
•VHBR, with 6.8 Mbit/s PCD to PICC framing and 3.4 Mbit/s PICC to PCD framing
•Up to 1.4 W output power with differential antenna
•Possibility of driving two antennas in single ended mode, with automatic antenna tuning
(AAT) system
•Inductive and capacitive Wake-up
•User selectable and automatic gain control
•Transparent and Stream modes to implement MIFARE®Classic compliant or other
custom protocols
The evaluation kit includes
•the STM32L476RET6, a 32-bit microcontroller with 512 KB of Flash memory
•a 105 mm x 52 mm, two turns antenna etched on the PCB, and its VHBR tuning circuit
•a Micro-USB connector for communication with the host PC and board powering
•six LEDs indicating the presence of the RF field and of the protocol used to communicate.
Figure 1. ST25R3911B-DISCO PCB (top view)
www.st.com

Contents UM2042
2/25 DocID029132 Rev 3
Contents
1 Quick start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1 USB connectivity and power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.2 STM32L4 MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.3 ST25R3911B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.4 Antenna and matching network components . . . . . . . . . . . . . . . . . . . . . . 8
2.3 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.1 PCB overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.2 PCB layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 Antenna matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Federal Communications Commission (FCC)
and Industry Canada (IC) compliance statements . . . . . . . . . . . . . . . . 22
4.1 FCC Compliance Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.1 Part 15.19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.2 Part 15.21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.3 Part 15.105 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.4 FCC ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2 Formal notices required by the Industry Canada (“IC”) . . . . . . . . . . . . . . 22
4.2.1 Compliance Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2.2 Declaration de Conformité . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.3 IC ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

DocID029132 Rev 3 3/25
UM2042 List of tables
3
List of tables
Table 1. NFC Forum matching alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 2. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

List of figures UM2042
4/25 DocID029132 Rev 3
List of figures
Figure 1. ST25R3911B-DISCO PCB (top view). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. Schematics overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 4. USB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 5. STM32L476 schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 6. ST25R3911B schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 7. Antenna and matching network schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 8. PCB overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 9. PCB layout, top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 10. PCB layout, mid layer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 11. PCB layout, mid layer 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 12. PCB layout, bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 13. VHBR matching with an AAT setting of 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 14. NFC Forum matching with an AAT setting of 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

DocID029132 Rev 3 5/25
UM2042 Quick start
24
1 Quick start
The ST25R3911B-DISCO is connected to a PC via USB to show the features of the
ST25R3911B chip. To do so, use the software STSW-ST25R001 to control all the functions
of the discovery kit.
1.1 Getting started
Connect the discovery kit to a PC using a micro USB cable. The USB port of the PC must be
capable of delivering at least 250 mA at 5 Volt supply.
To control the board, download the software STSW-ST25R001 from www.st.com and install
it. Further information on how to operate the software can be found in the user manual
UM2177 “PC software for the ST25R3911B-DISCO kit”, available on www.st.com.
1.2 System requirements
•Windows®PC (Windows 7 recommended)
•USB port, capable of delivering at least 250 mA at 5 V supply (1.25 W)
•Unit must be supplied by a Safety Extra Low Voltage (SELV) limited power source
through the USB port, the source should not exceed 60 VDC / 8 A / 100 VA
•Micro-USB cable

Hardware UM2042
6/25 DocID029132 Rev 3
2 Hardware
The PCB (Printed Circuit Board) is connected via USB to the PC. The STSW-ST25R001 PC
software controls the STM32 MCU located on the PCB. The STM32 MCU (based on Arm®
core) then operates the ST25R3911B via SPI.
The ST25R3911B is connected directly to the 5 V supply of the USB bus. An LDO converts
this voltage down to 3.3 V, to supply the microcontroller.
A green LED close to the USB plug indicates if the board is powered. Six blue LEDs indicate
the mode of operation (transmit / receive) and which technologies are in use.
The antenna runs along the PCB perimeter.
2.1 Block diagram
Figure 2 shows the functional block diagram of the board.
Figure 2. Functional block diagram
2.2 Schematics
As indicated in Figure 3, the schematics can be split into four main parts
•USB connectivity and power supply (Figure 4)
•STM32 MCU (Figure 5)
•ST25R3911B (Figure 6)
•Antenna and matching network components (Figure 7)
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DocID029132 Rev 3 7/25
UM2042 Hardware
24
2.2.1 USB connectivity and power supply
The ST25R3911B-DISCO board can be connected via USB to a host device.
Right behind the Micro-USB plug, an ECMF02 common mode filter with ESD protection for
USB 2.0 interface is placed. The common mode filter is connected to VBUS and to the
D+/D- data lines of the USB. All the USB terminals are ESD-protected by the built-in ESD
diodes of the ECMF02.
Additionally, the power supply filter for the 5 V supplies the 3.3 V LDO, which, in turn,
supplies the microcontroller.
A green LED is connected to the USB VBUS supply and shows the USB-power status.
2.2.2 STM32L4 MCU
This schematic includes the microcontroller needed to operate the NFC reader IC.
The MCU is clocked by a 32.768 kHz crystal. The MCU uses an internal PLL to generate the
48 MHz USB clock and the 80 MHz core clock from the provided 32.768 kHz.
Connector P201 is a JTAG/SWD interface to assist in software development. It can be
connected to an external ST-LINK/V2 device using a 9-pin Cortex®-M adapter.
The six blue LEDs (LED201 to LED206) show the current mode of communication. If
multiple protocols are active at the same time, then all corresponding LEDs are turned on.
The five resistors (R218 to R222) can be used to disconnect the MCU from SPI interface
header P204. This SPI cross-connect mode can be used to operate the ST25R3911B with a
different MCU PCB by cross connecting the ST25R3911B SPI to the second MCU PCB.
Connectors P202 and P203 can be used to connect an external UART or I2C host device to
the MCU.
2.2.3 ST25R3911B
The ST25R3911B is directly connected to the filtered 5 V USB supply, and there are
additional supply filtering components placed close to it. The jumper JP301 can be used to
measure the supply current of the chip. If this measurement is performed, the ferrite bead
L301 has to be removed.
Capacitors C301 to C304 provide additional filtering. All decoupling capacitors have been
placed as close as possible to the ST25R3911B. Special care has been taken for C310,
C302, C314 and C301, as they are the decoupling capacitors for the high power driver
stage.
In order to demonstrate the capacitive wake-up feature, two capacitive electrodes are
placed on the PCB. Additional electrodes can be connected using UFL connectors on P301
and P302.
For SPI cross-connecting to another reader PCB, the resistors R301 to R305 can be
removed. Then the STM32L4 MCU SPI can be connected to the ST25R3911B on any
customer PCB via header P204.
Thanks to J303 it is possible to bypass the internal VSP_RF regulator, this is required in
case output currents higher than 200 mA need to be supplied.

Hardware UM2042
8/25 DocID029132 Rev 3
2.2.4 Antenna and matching network components
This schematic contains the matching network and the automatic antenna tuning capacitors,
as well as the alternative NFC Forum matching components. In the default configuration,
the ST25R3911B-DISCO is populated with a VHBR matching, with communication speeds
up to 3.4 Mbps.
To support VHBR, the antenna is matched to a system Q-Factor of 8. By switching to the
NFC Forum matching components the system Q-Factor is increased to 16. This can
increase the read range up to 20%, depending on the used communication technology, but
limits the maximum supported communication bit rate to 848 kbps. Additional details about
antenna matching can be found on www.st.com/st25r.

UM2042 Hardware
DocID029132 Rev 3 9/25
Figure 3. Schematics overview
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U_Antenna
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SPI/Power_ConPM/USB_con
U_Microcontroller
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Figure 4. USB interface
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3V3
GND
3V3 LDO
GNDGND
USB Interface
USBD_P
USBD_N
V_RF
3_3V
PM/USB_con
GND
EN
1
GND
2
VO 4
NC 5 GND
0
VI
6PG 3
U102 LD39050PU33R
GND
ESD
G101
Logo_ESD
RoHS
G102
Logo_RoHS
ST25
G103
Logo_ST25
ST Microelectronics
G104
Logo_STM
L102
FB_0603_0R
L101
FB_0603
C104
C_1μ_0603_X5R
C103
C_1μ_0603_X5R
C106
C_2μ2_0402_X5R
C105
C_10n_0402_X7R
C102
C_10μ_0603_X5R
C101
C_10μ_0603_X5R
R101
LED101
PWR 1
D- 2
D+ 3
ID 4
Shield
6
GND 5
P101
μUSB
VBUS
1
D-
2
D+
3
ID
4
GND 5
D- 6
D+ 7
GND 8
U101
ECMF02-4CMX8
V_RF
V_RF
V_RF
3V3
J101
closed 0R
L103
FB_0603_0R
PM/USB_con
USBD_N
USBD_P
USBD_P
USBD_N