ST ST25R3911B User manual

December 2017 DocID029132 Rev 3 1/25

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

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

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

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

D D

C C

B B

A A

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Project Overview.SchDoc

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ST25R3911B-DISCO

MDG NFC & Reader Competence Center

PM/USB_con

U_Power Management

Power Management.SchDoc

Antenna_Con

U_Antenna

Antenna.SchDoc

SPI/Power_ConPM/USB_con

U_Microcontroller

Microcontroller.SchDoc

Antenna_ConSPI/Power_Con

U_ST25R3911B

ST25R3911B.SchDoc

Hardware UM2042

10/25 DocID029132 Rev 3

Figure 4. USB interface

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B B

A A

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MDG NFC & Reader Competence Center

3V3

GND

3V3 LDO

GNDGND

USB Interface

USBD_P

USBD_N

V_RF

3_3V

PM/USB_con

GND

VO 4

NC 5

GND

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

GND 5

P101

μUSB

VBUS

D-

D+

GND 5

D- 6

D+ 7

GND 8

U101

ECMF02-4CMX8

V_RF

3V3

J101

closed 0R

L103

FB_0603_0R

PM/USB_con

USBD_N

USBD_P

USBD_N

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