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ST ST25R3911B, User Manual

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ST ST25R3911B User Manual Download Page 21

DocID029132 Rev 3

21/25

UM2042

Antenna matching

24

          

With the new assembled values, the matching impedance looks as in 

Figure 14

, with a 

value close to 11 + j6 

Ω

.

Figure 14. NFC Forum matching with an AAT setting of 11

The HW based AAT algorithm will typically adjust to an AAT value of 11. Due to the higher 
Q-Factor the voltage on the antenna is also increasing. To put the receiver in an optimum 
signal level range, the capacitors C401 and C412 can be increased to 100 pF.

Table 1. NFC Forum matching alternatives

Default assembly

Value

NFC Forum replacement

Value

C403

80 pF

C403_NFCF

120 pF

C410

180 pF

C410_NFCF

120 pF

R401

3R9

R401_NFCF

1R96

R402

3R9

R402_NFCF

1R96

Summary of Contents for ST25R3911B

Page 1: ...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...

Page 2: ...tching 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 ...

Page 3: ...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 ...

Page 4: ... 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 ...

Page 5: ...vering 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...

Page 6: ... 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 connectivi...

Page 7: ...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 filt...

Page 8: ...911B 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 Add...

Page 9: ...ct Overview SchDoc Title Size Number Date File Revision Sheet of Time A4 ST25R3911B DISCO MDG NFC Reader Competence Center PM USB_con U_Power Management Power Management SchDoc Antenna_Con U_Antenna Antenna SchDoc SPI Power_Con PM USB_con U_Microcontroller Microcontroller SchDoc Antenna_Con SPI Power_Con U_ST25R3911B ST25R3911B SchDoc ...

Page 10: ...PM USB_con GND EN 1 GND 2 VO 4 NC 5 GND 0 VI 6 PG 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...

Page 11: ... 7 VSSA 12 VDDA VREF 13 VSS PF4 PA3 18 VDD PF5 19 VSS VCAP1 31 VDD 32 VSS VCAP2 PF6 47 VDD VUSB VSA PF7 48 BOOT0 60 VSS 63 VDD 64 PD2 54 U201B STM32L476RE 3V3 T_NRST Case S201 Case S202 3V3 1 2 3 4 P203 d n p 3V3 1 2 3 4 P202 d n p LP_UART_RX LP_UART_TX T_NRST T_JTDI T_SWO T_JTCK T_JTMS LED1 LED2 LED3 LED4 LED5 LED6 SEN MISO INTR MOSI SCLK SCLK_MCU MOSI_MCU IRQ_MCU MISO_MCU SS_MCU SDA SCL 3V3 C206...

Page 12: ...CLK_11 SEN_11 ST25R3911 NFC Initiator HF Reader Controller Interface Antenna Connection VSP_A VSP_D AGD V_RF GND GND GND SEN INTR MISO MOSI SCLK V_RF 3_3V MCU_CLK SPI Power_Con 3V3 JP301 d n p J303 open J302 d n p GND V_RF 3V3 C302 C_100n_0402_X7R C301 C_1μ_0402_X5R C304 C_100n_0402_X7R Y301 C308 C_8p2_0402 C307 C_8p2_0402 C309 C_10n_0402_X7R C310 C_10n_0402_X7R C311 C_10n_0402_X7R C312 C_10n_0402...

Page 13: ...a_Con Antenna Connection 1 2 J403 1 2 3 J402 C407 d n p C404 d n p NFC Forum matching GND GND RFI1 RFI2 RFI1 RFO1 RFO2 TRIM1_0 TRIM1_1 TRIM1_2 TRIM1_3 TRIM2_0 TRIM2_1 TRIM2_2 TRIM2_3 RFI2 C401 C_82p_0603 C412 C_82p_0603 C402 C_10p_0603 C411 C_10p_0603 C403 C_180p_0603 C410 C_180p_0603 C405 C_680p_0603 C409 C_680p_0603 L401 270n L402 270n C415 C_5p6_0402 C416 C_5p6_0402 C417 C_12p_0402 C418 C_12p_0...

Page 14: ...s close as possible to the positive and negative power supply pins for example VSP_RF and VSN_RF Since the chip is using a differential output driver stage the antenna matching network is treated as a differential network The space between the components is kept as small as possible and the whole network is routed in a completely symmetrical way Via stitching and via shielding is used to maintain ...

Page 15: ...ant analog traces are surrounded by GND vias Mid layer 1 This layer Figure 10 is a pure GND plane providing a low ohmic DC path for the GND connection Mid layer 2 Mid layer 2 Figure 11 is used for the power distribution It contains the power planes for the 5 V supply of the ST25R3911B and the 3 3 V supply of the microcontroller Bottom layer The bottom layer Figure 12 is mainly a GND plane but some...

Page 16: ...Hardware UM2042 16 25 DocID029132 Rev 3 Figure 9 PCB layout top layer ...

Page 17: ...UM2042 Hardware DocID029132 Rev 3 17 25 Figure 10 PCB layout mid layer 1 ...

Page 18: ...Hardware UM2042 18 25 DocID029132 Rev 3 Figure 11 PCB layout mid layer 2 ...

Page 19: ...UM2042 Hardware DocID029132 Rev 3 19 25 Figure 12 PCB layout bottom layer ...

Page 20: ...nymore but the read range for lower data rate applications will increase up to 20 The matching impedance will remain the same when switching between the two matchings VHBR matching The VHBR matching is designed with a target Q Factor of 8 The matching impedance is around 12 8 j5 Ω The HW based AAT algorithm will typically adjust to an AAT value of 8 see Figure 13 Figure 13 VHBR matching with an AA...

Page 21: ...lgorithm will typically adjust to an AAT value of 11 Due to the higher Q Factor the voltage on the antenna is also increasing To put the receiver in an optimum signal level range the capacitors C401 and C412 can be increased to 100 pF Table 1 NFC Forum matching alternatives Default assembly Value NFC Forum replacement Value C403 80 pF C403_NFCF 120 pF C410 180 pF C410_NFCF 120 pF R401 3R9 R401_NFC...

Page 22: ... equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instructions may cause harmful interference to radio communications However there is no guarantee that interference will not occur in a particular installation If this equipment does cause harmful interference to radio or television reception which can be determined by turning the ...

Page 23: ... aux CNR d Industrie Canada applicables aux appareils radio exempts de licence L exploitation est autorisée aux deux conditions suivantes 1 l appareil ne doit pas produire de brouillage et 2 l utilisateur de l appareil doit accepter tout brouillage radioélectrique subi même si le brouillage est susceptible d en compromettre le fonctionnement 4 2 3 IC ID IC ID 8976B R3911BD1 ...

Page 24: ...nges 23 Jun 2017 1 Initial release 25 Jul 2017 2 Added Section 4 1 3 Part 15 105 Updated Section 4 1 4 FCC ID and Section 4 2 3 IC ID Updated Figure 8 PCB overview Figure 9 PCB layout top layer and Figure 12 PCB layout bottom layer 15 Dec 2017 3 Updated Figure 1 ST25R3911B DISCO PCB top view Updated Section 2 Hardware ...

Page 25: ...chasers are solely responsible for the choice selection and use of ST products and ST assumes no liability for application assistance or the design of Purchasers products No license express or implied to any intellectual property right is granted by ST herein Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product...

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