UM2742 User manual - STMicroelectronics

November 2020 UM2742 Rev 2 1/44

1

UM2742User manual

High-power RFID reader system based on ST25RU3993

Introduction

The ST25RU3993-HPEV is a high-power RAIN® (UHF) RFID reader system based on the integrated reader IC ST25RU3993.

The purpose of ST25RU3993-HPEV is to provide a comprehensive RAIN RFID reader system that allows the user to evaluate the properties and the features of ST25RU3993. To achieve this goal the ST25RU3993-HPEV board, differently from a typical reference design approach, combines a high RF power and a low RF power RFID reader on a single PCB.

Additionally, the ST25RU3993-HPEV board has been outfitted with numerous easy to access test points and measurement possibilities. With minor modification effort it is possible to change the architecture of the reader. For example, it is possible to control the RF circuitry with external MCU or vice versa. Bypassing the external on-board power amplifier or alternate antenna configurations are additional possibilities.

The ST25RU3993-HPEV is controlled by a graphical user interface (GUI) running on a host PC. The corresponding interface is a USB/UART bridge (requires driver installation). The GUI can be found on dedicated pages on www.st.com.

The board supports tuning the radio frequency from 840 to 960 MHz. and provides two SMB (male) antenna connectors that can be controlled via the GUI. To enable scanning for RAIN RFID transponders connect a suitable 50 Ω UHF antenna for the targeted frequency range.

Figure 1. ST25RU3993-HPEV board

www.st.com

http://www.st.com

Contents UM2742

2/44 UM2742 Rev 2

Contents

1 Standard connection setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.1 Board features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Hardware description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 RF circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Microcontroller and connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Firmware programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.4 Boot mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.5 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.6 Test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.6.1 Analog test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.6.2 Digital test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.6.3 Probing RF signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4 PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

UM2742 Rev 2 3/44

UM2742 List of tables

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List of tables

Table 1. TXCO / Crystal configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Table 2. MCU interfaces and buttons (see Figure 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Table 3. MCU - SPI interface and ST25RU3993 connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 4. SPI interface pinout at J10, J12 and J13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 5. UART connections and pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table 6. MCU connections to buttons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table 7. MCU connections to LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Table 8. MCU connections to RF switches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Table 9. Connections to JLINK (SWD) interface and pinout of connector . . . . . . . . . . . . . . . . . . . . 17Table 10. Typical voltage levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Table 11. Connection of components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Table 12. Connections of analog test points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 13. Supply voltages of analog test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 14. RF test points – Default power levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Table 15. List of schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Table 16. PCB stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Table 17. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Table 18. DC characteristics (VBUS = 5.0 V, 25 °C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Table 19. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

List of figures UM2742

4/44 UM2742 Rev 2

List of figures

Figure 1. ST25RU3993-HPEV board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Figure 2. Standard connection setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 3. ST25RU3993-HPEV functional diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 4. Power detector voltage characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 5. Main digital interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Figure 6. JLink connection using the needle adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Figure 7. Entering the Boot mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Figure 8. Test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Figure 9. Connection of a voltmeter / ammeter to the supply voltage test points . . . . . . . . . . . . . . . 23Figure 10. RF test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Figure 11. Connecting to the RF test points with the SMA adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Figure 12. System overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Figure 13. UHF RFID reader IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Figure 14. External power amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Figure 15. Carrier cancellation circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Figure 16. Antenna switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Figure 17. RF shield. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Figure 18. USB supply / UART bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Figure 19. Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Figure 20. Supply LDOs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Figure 21. External interfaces and connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Figure 22. Top layer layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Figure 23. RF GND layer (L2), GND layer (L4) and bottom layer (L6) layout . . . . . . . . . . . . . . . . . . . 39Figure 24. Power layer (L3) layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Figure 25. Routing layer (L5) layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

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UM2742 Standard connection setup

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1 Standard connection setup

The typical reader setup is shown in Figure 2.

Figure 2. Standard connection setup

The host PC running the GUI is connected via a Micro-USB cable. The external power amplifier on the ST25RU3993-HPEV board is powered through the 6 V power adapter and must be connected when the external PA TX option is used. The antenna is connected to the active antenna port through a coaxial cable. A transponder is within the antenna range.

1.1 Board features

ST25RU3993 RAIN (UHF) RFID reader IC

ISO/IEC 18000-63:2015 / Gen2V2

GB/T 29768-2013

Two SW-controlled power amplifier (PA) options:

– External PA: 30 dBm max. TX power

– Internal PA: 17.5 dBm max. TX power

Configurable TX power level

Power detector to monitor TX power

Automatic carrier cancellation for improved RX sensitivity

Differential RX input

RX sensitivity:

– -80 dBm at 90% read success, one sideband of tag response (ISO18046-3: 2012)

– -77 dBm at 90% read success, both sidebands of tag response(ISO18046-3: 2020)

Adaptive / manual RX gain adjustment

Tunable radio frequency: 840 to 960 MHz

Minimum frequency step: 25 kHz

External frequency reference (20 MHz) assembly option

Adaptive / manual anti-collision slot options

Continuous wave or Modulated RF output test modes

Standard connection setup UM2742

6/44 UM2742 Rev 2

Two antenna ports: SMB (M)

Automatic / Manual antenna port switching

Carrier sense TX option (LBT)

UHF tag RSSI measurement

Configurable SELECT command mask

UHF transponder EPC Read / Write

Transponder read based applications trigger

Custom reader TX command editor tool

Customizable Gen2 TX commands

Direct TX modulation through MCU for proprietary protocol support

Store / Recall reader configuration

Register map

Buzzer

Host interface and supply

– USB/UART bridge

– USB receptacle: Micro, B-Type

– Main supply: 6 V DC jack

MCU:

– STM32L476RGT6 (Arm®(a) 32-bit Cortex®-M4)

– 64 MHz

– 128-Kbyte RAM

– 1-Mbyte Flash memory

– SPI Mode 1 (5 MHz)

– Firmware programmable through USB/UART

– SWD debug interface

– LED indicators

– Power amplifier selection

– Carrier cancellation tuning activity

– Carrier cancellation tuning OK

– OSC OK (20 MHz external reference)

– PLL OK

– RF ON

– No tag response

– Tag CRC error

– Tag found

Test points:

– In-circuit RF power levels and signals

a. Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

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UM2742 Standard connection setup

43

– RFID communication TX and RX

– UART and SPI signal lines

– UART_LOG for debugging purposes

– Control voltage of internal VCO

– RF power detector output voltage

– 20 MHz reference signal

– External PA BIAS voltage

– LDO output voltages

– LDO outputs: jumpers for current consumption measurement

– Main supply: jumper for current consumption measurement

– Antenna switch state

– Power amplifier selection switch state

Buttons:

– MCU reset

– MCU boot mode

Standard connection setup UM2742

8/44 UM2742 Rev 2

Figure 3. ST25RU3993-HPEV functional diagram

IRQ

EN

RF switch:

SKY13431-374LF

Carrier cancellation

circuit

SPI (Mode 1)

5V

RX

TX

D-

D+ USB connector:

MICRO-B

3.3V 3.6V

LDO:

LD39100PUR

PA_LDO_EN

PA_SW_V1

PA_SW_V2

ANT_SW_V2

ANT_SW_V1

CPL-10dB

CPL-20dB

RFOPX RFONX PAOUT_P PAOUT_N

93_RF_OUT

93_intPA

PA_OUT

LP_Filter_IN

LP_Filter_OUT

TX_RX

TX

Power detector:

MAX4003EUA

ANT1 ANT2

ETC_x

MOSI

CLK

RF_Detector

SWD connector: (TC2050-IDC-FP)

SWD

Buzzer:

PKMCS0909E4000

OSCO

3.3V

3.3V

3.3V

3.3V

3.3V

LDO:

LD39100PUR

LED: MCU

LED: RF ON

LED: Tuning

LED: Tuned

LED: OSC OK

LED: ANT1

LED: ANT2

LED: NO Tag Resp

LED: Tag CRC Err.

LED: Tag

LED: Int_PA

LED: Ext_PA

LED: PLL OK

SPI + IRQ + EN

Carrier cancellation CS

UART

UART_LOG_TX

PA_LDO_EN

OSCO

VCO

EXT_PA_BIAS

RF detector

Button: RESET

Button: BOOT

Legend

Component Test point / connector

LED Button Logic Supply

DC power jack OD: 6.4 mm ID: 2.1 mm

6V

OSCI

Antenna selection switch state

PA selection switch state

LED: BOOT (red)

VBUS 5V VBUS 5V

USB/UART bridge:

FT231XQ-R

Balun:

BD0810J50100AHF

20 dB coupler:

DC1722J5020AHF

Low pass filter:

0900LP15B0063

10 dB coupler:

DC1722J5020AHF

TCXO:

TXEAADSANF-20

Crystal:(optional)

NX3225SA-20

Antenna port 2

SMB Male

Antenna port 1

SMB Male

6V

VBUS 5V

4

3

4

RF Analog

RF switch:

SKY13431-374LF

PA LDO:

LD39100PUR

RX

MIX_INP

MIX_INN

MCU:

STM32L476RG

Power amplifier:

TQP9107

Balun:

BD0810J50100AHF

Balun:

0900BL15C050

UHF RFID reader IC:

ST25RU3993

UM2742 Rev 2 9/44

UM2742 Hardware description

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2 Hardware description

2.1 RF circuit

The main component of the RF circuit is the ST25RU3993 device, which receives digital baseband transmit data and commands from the MCU via the SPI interface. It then frames these data and automatically encodes them into PIE symbols. Based on the PIE encoded symbols ST25RU3993 creates a sinusoidal shaped modulation signal (either ASK or PR-ASK), which modulates the RF carrier. ST25RU3993 synthesizes its RF carrier frequency with a VCO / integer-n phase locked loop (PLL). The frequency reference for the PLL can be either a 20 MHz crystal oscillator or a temperature compensated crystal oscillator (TCXO).

As shown in Table 1 the ST25RU3993-HPEV board accommodates both options, the default configuration is the TCXO with a clipped sine wave output wave having 0.8 Vpp amplitude. With a small modification it is possible to connect the existing crystal.

The output of the internal PLL- charge pump is connected to LF_CEXT (pin 45), and the external part of the loop filter is placed in close proximity to it. An additional low-pass filter stage is integrated in ST25RU3993 and is part of the loop filter circuit. The loop filter output is the control voltage of the internal VCO.

Table 1. TXCO / Crystal configuration

Default Alternate (modified by user)

TCXO connected to ST25RU3993 Crystal connected to ST25RU3993

R54 and R55 not populated C51 removed, R54 and R55 populated

Hardware description UM2742

10/44 UM2742 Rev 2

The ST25RU3993 has two differential output port pairs. The low power output and the internal power amplifier output. Depending on which differential output port pair is activated the modulated carrier frequency will be amplified and output accordingly.

The low power output is intended for external signal amplification for a long read range configuration of the ST25RU3993-HPEV reader. The low power output with its differential output pin pairs RFONX (23) and RFOPX (24) is connected to a 2:1 balun, where the transmit signal is transformed from a 100 differential to 50 Ω single-ended signal. The output stage of the low power output is supplied by the VDD_B voltage generated and regulated by ST25RU3993 itself. L3 and L4 act as a RF choke, C57 and C58 as bypass capacitors and C65 and C54 as DC blocking capacitors. The signal then proceeds to the external power amplifier to generate a high-power output signal with approximately 31 dBm in ST25RU3993-HPEV default transmit power configuration.

The internal power amplifier is used for the short read range configuration of the reader. The output pins of the internal power amplifier are PAOUT_N (16, 17) and PAOUT_P (20, 21). A matching network and a 1:1 balun transforms the output of the internal power amplifier to a 50 Ω single-ended signal. The internal power amplifier is supplied by the on-chip generated and regulated voltage VDD_PA. L1, L2 are acting as RF chokes, C12 and C14 are bypass capacitors. After the balun the output power of the internal power amplifier is tipically 20 dBm.

Both RF output options the external power amplifier and the output of the internal power amplifier are connected to an RF-switch which is controlled by the PC software (GUI) of the ST25RU3993-HPEV reader. Only one RF output option can be active at a time. Note a UHF RFID reader reference would typically offer only one RF output and hence the PA RF-switch would be stripped from the design avoiding it’s introduced insertion loss of ~0.5 dB. So would be the DC blocking capacitors which this RF-switch requires on all its RF terminals. The output of the RF-switch is connected to a low-pass filter which attenuates the second and third harmonic of the carrier frequency. The filtered transmit signal is then connected to a 20 dB directional coupler, which takes a negligible small portion of the transmit power, which is further attenuated by a pi-pad attenuator. The limited TX power sample is then fed to the input a logarithmic power detector that converts the RF power to a corresponding DC voltage. The output DC voltage of the power detector versus the generated RF power is shown in Figure 4.

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Figure 4. Power detector voltage characteristics

The DC output voltage of the power detector is connected to an ADC input pin (PA1) of the microcontroller.

The majority of RF transmit power which passes through the 20 dB directional coupler is fed to the main directional coupler. The main directional coupler has a coupling factor of 10 dB and acts as the directional unit which should isolate the transmit from the receive path of ST25RU3993. The main directional coupler plays a very important role in the RFID reader system as its parasitics have a great influence on the sensitivity of the reader. The main directional coupler essentially has four terminals:

1. Input

2. Direct

3. Coupled

4. Isolated

The direct terminal is connected to the second RF switch in the reader system. This switch directs the transmit power to either antenna port 1 or antenna port 2. The antenna switch again requires DC blocking capacitors on all its RF terminals. Both antenna ports are SMB (male) type.

To avoid reducing the sensitivity of the reader the self-jamming signal reaching the receiving inputs of ST25RU3993 must be minimized. The self-jamming signal comprises reflections from the antenna (S11) and the leakage across the main directional coupler. To minimize it a carrier cancellation circuit is connected to the coupled port of the main directional coupler.


12/44 UM2742 Rev 2

The carrier cancellation circuit is able to change its impedance and hence to reflect a certain amount of the coupled power back into the directional coupler. This reflected signal is combined with the self-jamming signal at the isolated port of the main directional coupler. The isolated port of the main directional coupler is connected to the receiving pins of ST25RU3993. If the signal reflected by the carrier cancellation circuit has the same amplitude and opposite phase of the self-jammer the signals cancel them out and vanish.

The main components of the CCC are three digital tunable capacitors controlled by the STM32L476RG microcontroller via SPI. The lumped components of the carrier cancellation circuit help to define its tuning range around 50 Ω and define the impedance step created by one LSB change of a digital tunable capacitor.

The isolated port of the main directional coupler is connected to a 2:1 balun to transform the incoming tag response signal to a 100 Ω differential signal that is fed into ST25RU3993 receiver section at pins MIX_INP (4) and MIX_INN (6).

2.2 Microcontroller and connections

Table 2. MCU interfaces and buttons (see Figure 5)

A MCU reset button

B USB receptacle: Micro, B-Type

C 6 V DC power connector: 5 mm barrel connector

D ST25RU3993 Rain (UHF) RFID reader IC

E Enable line connection of power amplifier LDO

F UART interface connections

G MCU boot mode button

H STM32L476RGT6 (Arm® 32-bit Cortex®-M4)

J SWD debug interface connections

L, M SPI bus interface connections

N UART_LOG connection for debugging purposes

K Carrier cancellation circuit (CCC) SPI chip select lines

O PA output selection switch state

P Antenna port selection switch state

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43

Figure 5. Main digital interfaces

The ST25RU3993-HPEV is controlled by STM32L476RG, a ultra-low-power MCU with FPU Arm Cortex-M4 core, 80 MHz, 1 Mbyte Flash memory, LCD, USB OTG, DFSDM.

MS53587V1

A B C

O

P

F

K

L

N

M D

E

JHG


14/44 UM2742 Rev 2

The MCU is supplied by 3.3 Volts, regulated by an adjustable LDO. The clock source is an external crystal generating 32.768 kHz, connected to OSC32_in (3) and OSC32_out (4). It interfaces the host PC via UART for which a USB/UART bridge is used.

The MCU communicates with the ST25RU3993 via an SPI interface controlling the ST25RU3993 lines ENABLE and IRQ. The SPI interface operates in mode 1 with a 6 MHz serial clock. The SPI interface is also used to control the digital tunable capacitors for the carrier cancellation circuit.

The MCU controls the RF switches for changing the power amplifier and the active antenna port. The analog output of the RF power detector is connected to one of its ADC inputs (PA1) to convert the DC voltage corresponding to the transmit RF power into a digital representation. The LDO for the external power amplifier is enabled by the MCU, making it possible to completely shut down the external power amplifier when RF power needs to be OFF, e.g. as required for carrier sense (LBT). One pin (UART LOG) is reserved to act as a generic debug pin or to be programmed as a trigger output for an external measurement equipment.

Table 3. MCU - SPI interface and ST25RU3993 connections

Component U1 Component U5 Component U6 Component U7 Component U8

MCU pin ST25RU3993 pin DTC1 pin DTC2 pin DTC3 pin

Name Number Name Number Name Number Name Number Name Number

PA4 20 NCS 33 - - - - - -

PA5 21 SCLK 37 CLK 5 CLK 5 CLK 5

PA6 22 MISO 34 - - - - - -

PA7 23 MOSI 35 SDAT 7 SDAT 7 SDAT 7

PC7 38 - - - - - - SEN 6

PC8 39 - - - - SEN 6 - -

PC9 40 - - SEN 6 - - - -

PA9 42 IRQ 32 - - - - - -

PA10 43 EN 31 - - - - - -

Table 4. SPI interface pinout at J10, J12 and J13

Component U5 Component U6 Component U7 Component U8 J10 J12 J13

ST25RU3993 pin DTC1 pin DTC2 pin DTC3 pin Connectorpin number

Name Number Name Number Name Number Name Number

SCLK 37 CLK 5 CLK 5 CLK 5 1 - -

MISO 34 - - - - - - 3 - -

MOSI 35 SDAT 7 SDAT 7 SDAT 7 2 - -

- - - - - -ETC3SEN

6 - 3 -

UM2742 Rev 2 15/44


43

- - - -ETC2SEN

6 - - - 2 -

- -ETC1SEN

6 - - - - - 1 -

OAD2 - - - - - - - - - 1

OAD - - - - - - - - - 2

EN 31 - - - - - - - - 3

IRQ 32 - - - - - - - - 4

NCS 33 - - - - - - - - 5

ADC - - - - - - - - - 6

Table 4. SPI interface pinout at J10, J12 and J13 (continued)

Component U5 Component U6 Component U7 Component U8 J10 J12 J13

ST25RU3993 pin DTC1 pin DTC2 pin DTC3 pin Connectorpin number

Name Number Name Number Name Number Name Number

Table 5. UART connections and pinout

Component U1 Component U13 J7

MCU pin FTDI pinConnector pin

numberName Number Name Number

NRST 7 RTS 19 1

BOOT0 60 DTR 18 2

PA3 17 TXD 17 3

PA2 16 RXD 1 4

Table 6. MCU connections to buttons

Component U1 Component B1 Component B2

MCU pin Reset button Boot button

Name Number Name Number Name Number

NRST 7 1 1 2 2

BOOT0 60 - - 5 5


16/44 UM2742 Rev 2

Table 7. MCU connections to LEDs

Component U1D1 D2 D3 D4 D5 D6 D7 D8 D11 D12 D13 D16 D17

MCU pin

Na

me

Nu

mb

er

MC

U_

LE

D

intP

A_L

ED

RF

_LE

D

extP

A_

LE

D

TU

NIN

G_L

ED

TAG

_L

ED

PL

L_L

ED

OS

C_L

ED

TU

NE

D_L

ED

NO

_RE

SP

_LE

D

CR

C_E

RR

_LE

D

AN

T1_

LE

D

AN

T2_

LE

D

PA0 14 1 (C) - - - - - - - - - - - -

PD2 54 - 1 (C) - - - - - - - - - - -

PC10 51 - - 1 (C) - - - - - - - - - -

PB4 56 - - - 1 (C) - - - - - - - - -

PC12 53 - - - - 1 (C) - - - - - - - -

PC8 37 - - - - - 1 (C) - - - - - - -

PB12 33 - - - - - - 1 (C) - - - - - -

PB13 34 - - - - - - - 1 (C) - - - - -

PC11 52 - - - - - - - - 1 (C) - - - -

PB14 35 - - - - - - - - - 1 (C) - - -

PB15 38 - - - - - - - - - - 1 (C) - -

PB2 28 - - - - - - - - - - - 1 (C) -

PB1 27 - - - - - - - - - - - - 1 (C)

Table 8. MCU connections to RF switches

Component U1 Component S1 Component S2

MCU pin PA switch pin Antenna switch pin

Name Number Name Number Name Number

PB0 26 V1 1 - -

PC5 25 V2 3 - -

PB10 29 - - V1 1

PB11 30 - - V2 3

UM2742 Rev 2 17/44


43

2.3 Firmware programming

There are two options to program the firmware of the STM32L476RG microcontroller:

1. The simplest way to program a new firmware version to the MCU is by connecting the ST25RU3993-HPEV board to the host PC with the micro USB cable and use the Firmware Update function of the GUI. For more information about this option refer to the user manual of the GUI.

2. Alternatively, the firmware can be programmed to the MCU using the ST-LINK connected to the JLINK (SWD) interface (see Figure 6) with a J-Link needle adapter (e.g. 8.06.04 J-LINK 10-PIN NEEDLE ADAPTER). For more information about this option refer to the user manual of the ST-LINK/V2.

Table 9. Connections to JLINK (SWD) interface and pinout of connector

Component U1 Component P3

MCU pin JLINK pin

Name Number Name Number

- - VDD 1

PA13 46 SWDIO 2

- - GND 3

PA14 49 SWCLK 4

- - GND 5

PB3 55 SWO 6

- - NC 7

PA15 50 TDI 8

- - NC 9

NRST 7 MCU RESET N 10


18/44 UM2742 Rev 2

Figure 6. JLink connection using the needle adapter

UM2742 Rev 2 19/44


43

2.4 Boot mode

To enter the STM32L476RG boot mode press and hold the BOOT button (1) while the RESET button (2) is pressed (see Figure 7). At this point the boot mode is active and both buttons can be released.

Figure 7. Entering the Boot mode

2.5 Power supply

The ST25RU3993-HPEV is supplied through the USB Interface (VBAT) and an external 6 V supply connected to J14 a DC power jack. J14 has a hot inner contact with 2.1 mm diameter suitable for a 5.5 mm barrel plug.

MS53599V1

2

1


20/44 UM2742 Rev 2

The 5V (VBAT) supply rail is distributed to two low-dropout regulators which supply:

LDO U9 – for powering digital components (3V3),

LDO U10 - for powering RF components (VSUP)

The 6 V DC input is dedicated to supply the power amplifier supply via an LDO U11 regulating the supply rail VPA.

Table 10. Typical voltage levels

Voltage domain Voltage (V)

3V3 3.3

VSUP 3.6

VPA 5.0

Table 11. Connection of components

Voltage domain Schematic Component(s) Pin name(s) Pin number(s)

5 V (VBUS)

Supply (Figure 20) U9, U10VI 6

EN 1

USB interface (Figure 18)

U13 VCC 12

6 V Supply (Figure 20) U11VI 6

EN 5

3V3

External interfaces (Figure 21)

P3 1 1

Controller (Figure 19)

U1

VBAT 1

VDD 19, 32, 48, 64

VDD / VREF+(1) 13

NRST(2) 7

BOOT0(3) 60

Power amplifier (Figure 14)

U3VCC 8

/SHDN 2

UHF_RFID (Figure 13)

U4 VCC(4) 4

U5 VDD_IO 38

Carrier cancellation (Figure 15)

U6, U7, U10 VDD 4

USB interface (Figure 20)

U13 VCCIO 20

VSUP (3.6 V)UHF_RFID (Figure 13)

U5 VEXT(5) 11

U5 VEXT_PA(6) 14

UM2742 Rev 2 21/44


43

VPA (5 V)Power amplifier

(Figure 14)

U2 VPD1 12

U2 VPD2 11

U2 VCC 2

U2 VBIAS(7) 1

1. Via ferrite bead FB3.

2. Via pull-up resistor R61.

3. Via push button B2.




7. Via R21.

Table 11. Connection of components (continued)

Voltage domain Schematic Component(s) Pin name(s) Pin number(s)


22/44 UM2742 Rev 2

2.6 Test points

The ST25RU3993-HPEV board provides several test points (see Figure 8) that allow the user to test and evaluate circuit nodes in the ST25RU3993 reader design.

Figure 8. Test points

MS54000V1

5 V

3.3 V

VPA

VSUP

ATP3ATP4ATP1

Digital

ATP2

UM2742 Rev 2 23/44


43

2.6.1 Analog test points

Two test points are placed at the output of the three LDOs to easily measure the regulated voltage of each voltage domain. A GND pad is placed close to the voltage test points for accurate voltage measurements (left side of Figure 9).

The current consumption of the three regulated voltage domains can be measured separately. To enable this kind of measurement a 0 Ω resistor (R3) must be removed (right side of Figure 9). Make sure to restore the connection once the measurement is done, before reverting to normal operation.

Figure 9. Connection of a voltmeter / ammeter to the supply voltage test points

Table 12. Connections of analog test points

Component U5 U2 U3

Pin Name Number Name Number Name Number

Test point

ATP1 OSCO 30 - - - -

ATP2 VCO (LF_CEXT) - - - -

ATP3 - - VBIAS 1 - -

ATP4 - - - - OUT 7

Table 13. Supply voltages of analog test points

5 V (VBUS) 3V3 digital supply VSUP RF VPA power amplifier

P2 J5 J20 J21

Pin no. Pin name Pin no. Pin name Pin no. Pin name Pin no. Pin name

1 VBUS 1 GND 1 GND 1 GND

2 VBUS 2, 3 3V3 2, 3 VSUP 2, 3 VPA

MS54018V1

ARemove R3

V


24/44 UM2742 Rev 2

2.6.2 Digital test points

In addition to the four test points shown above a test point for each LED connected to the STM32L476RG controller is available.

2.6.3 Probing RF signals

The ST25RU3993-HPEV board features four RF test points (see Figure 10) to measure RF power levels in-circuit. The test point connectors have a switch built-in that disconnects the remainder of the circuit when the test adapter (MS-156-HRMJ-2) is mated. This allows the user to perform measurements with a proper line termination.

PLL OK Indicates that the PLL of ST25RU3993 is locked and the carrier frequency is stable.

OSC OK Active low. Indicates that the reference frequency for the PLL is stable.

No tag response :Pulled low if the sent reader command is not replied by a tag.

Tag CRC error Pulled low if a CRC error is detected within a tag response.

Tag found Pulled low every time a tag has been inventoried.

EXT_PA Pulled low if the reader is in its long read range configuration.

INT+PA Pulled low if the reader is in its short read range configuration.

TUNING Pulled low if the reader currently is re-tuning the carrier cancellation circuit.

Tuned Active low. Indicates that the self-jamming signal is sufficiently suppressed.

RF ON Active low. Indicates that the RF carrier is ON.

ANT1 Active low. Indicates that antenna port 1 is active.

ANT2 Active low. Indicates that antenna port 2 is active.

UM2742 Rev 2 25/44


43

Figure 10. RF test points

MS54019V1

RF-TP2RF-TP1

RF-TP3

RF-TP4


26/44 UM2742 Rev 2

Figure 11. Connecting to the RF test points with the SMA adapter

Table 14 lists the typical power levels that can be expected while the ST25RU3993-HPEV board operates in its default configuration.

Table 14. RF test points – Default power levels

RF test point Description Power level

RF-TP1ST25RU3993 RF output signal (single-ended). To evaluate the power and the spectral properties of the RF signal at the low power output.

-1.9 dBm

RF-TP2External power amplifier output. To evaluate the power and the spectral properties of the RF signal.

33 dBm

RF-TP3Internal power amplifier RF output. To evaluate the power and the spectral properties of the RF signal.

20.5 dBm

RF-TP4RX signal. To evaluate the self-jammer signal level or a RN16 tag response. When connected no tag communication is possible.

-

UM2742 Rev 2 27/44

UM2742 Schematics

43

3 Schematics

Table 15. List of schematics

Module Reference

System overview Figure 12

UHF RFID reader IC Figure 13

External power amplifier Figure 14

Carrier cancellation circuit Figure 15

Antenna switch Figure 16

RF shield Figure 17

USB supply / UART switch Figure 18

Microcontroller Figure 19

Supply LDOs Figure 20

External interfaces and connectors Figure 21

Sc

he

ma

tics

UM

274

2

28/4

4U

M2

742 R

ev 2

Figure 12. System overview

1

1

2

2

3

3

4

4

D D

C C

B B

A A

93_RF_OUT

SPI

93_Signals

RX_D

93_intPA

OSCO

VCO

UHF RFID ReaderUHF_RFID_HP.SchDoc

93_RF_OUT TX

PA_SW_V2

RF_Detector

93_intPA

ext_PA_BIAS

PA_SW_V1

Power AmplifierPower_Amplifier_HP.SchDoc

Project PageProject_Page_HP.SchDoc

SPI

93_Signals

Carrier_CancellationJLINK

PA_LDO_EN

MUC_RESET_N

UART_LOG_TX

OSCO

VCO

ext_PA_BIAS

RF_Detector

UART

ANT_SW_V1

ANT_SW_V2

PA_SW_V2

PA_SW_V1

External InterfacesExternal_Interfaces_HP.SchDoc

SPI

UART

93_Signals

JLINKCarrier_Cancellation

PA_LDO_EN

PA_SW_V2

MUC_RESET_N

UART_LOG_TX

ANT_SW_V1

RF_Detector

PA_SW_V1

ANT_SW_V2

Plug_Enable

ControllerController_HP.SchDoc

TX

Carrier_Cancellation

SPI

RX_D

TX_RX

Carrier CancellationCarrier_Cancellation_HP.SchDoc

PA_LDO_ENPlug_Enable

DC SupplySupply_HP.SchDoc

Title PageTitle_Page_HP.SchDoc

UART

USB InterfaceUSB_Interface_HP.SchDoc

MechanicalMechanical_HP.SchDoc

ANT_SW_V2

TX_RX

ANT_SW_V1

Antenna SwitchAntenna_Switch_HP.SchDoc

UM

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42S

chem

atics

UM

2742

Re

v 229

/44

Figure 13. UHF RFID reader IC

1

1

2

2

3

3

4

4

D D

C C

B B

A A

NC

S

GNDGND

GNDGND

GND GND

GNDGND

GND

GND

GND

GND GND

MIS

O

MO

SI

CLK

IRQ

EN

LF_CEXT

LF_CEXT

GND GND

VDD_B

VDD_B

GND

GND

93_RF_OUT

OA

D

OA

D2

GND

GND

VSUP

MISOMOSI

CLKSPI

IRQEN

NCSADCOAD

OAD2

93_Signals

IRQ

GND

GNDGNDGNDGND

GNDGNDGNDGNDGNDGND

RX_P

RX_N

RX_D

CLK

MOSIMISO

NCS

EN

OADOAD2

R33

15k

C553n9F

C50100nF

C592u2F

C612u2F

C632u2F

C71

2u2F

C73

2u2F

C75

2u2F

C852u2F

C84

2u2F

C522u2F

C892u2F

C782u2F

C7910nF

C8010nF

C8110nF

C8210nF

RFO_P

RFO_N

TX

_P

TX

_N

IN_

P

IN_

N

RX_P

RX_N

RFO_P

RFO_N

GND

Vdd_PA

GND

GND

GND

GND

C3

1p2F

C1

1p2F

L230nH

L130nH

C4

15pF

C5

15pF

C75p6F

C65p6FL15

3n6H

L103n6H

GND 2

UB 1

B24

B13

NC6GND

UB

B2

B1

NC

GND 5

T3Balun

93_intPA

Vdd_PA

GND

VBPD

GND

GND

GND

R540R DNP

R55

0R DNPADC

3V3

3V3

ADC

X320 MHZ

CD2

CD1

AGD

VOSC

VDD_A

VDDLF

COMP_A

CO

MN

_A

COMP_B

CO

MN

_B

CB

V

CB

IB

VD

D_

MIX

PAOUT_N

PAOUT_P

OS

CO

OS

CI

OSCO

VCO

GND GND

C662u2F

C76120pF

C7230 pF

C3430 pF

C7430 pF

C64

120pF

C62120pF

C60120pF

Low ESL

C69100nF

C9382pF

C9482pF

GNDG1

GNDG2

IO

J9

COAX JACK

C14120pF

C12120pF

C5482pF

C6582pF

C57120pF

C58120pF

C51220nF

FB4

1k

C11111pF

C11011pF

GND

C3282pF

COMN_A48

CO

MP

_B1

CO

MN

_B

2

VD

D_L

FI

3

MIX

_IN

P4

MIX

_IN

N6

VS

S/M

IXS

_IN

5

CB

IB9

VD

D_M

IX10

CB

V8

VD

D_T

XPA

B7

VE

XT

11

VDD_PA13

VD

D_B

12

PAOUT_N17

PAOUT_N16

VEXT_PA14

VSN15

VSN18

VSN19

PAOUT_P20

PAOUT_P21

VSN22

OA

D2

26

OA

D2

7

RFONX23

RFOPX24

VS

N2

5

OS

CO

30

VD

D_D

28

EN

31

IRQ

32

OS

CI

29

NC

S3

3M

ISO

34

MO

SI

35

CL

SY

S3

6

SCLK37

VDD_IO38

CD240

CD141

AGD42

ADC39

VDD_A44

LF_CEXT45

VOSC43

VDDLF46

COMP_A47

49 EP

ST25RU3993UHF RFID

Integrated Reader IC

U5ST25RU3993

C91

0.47uF

VEXT_PA

VEXT_PA

FB5

1kLow ESL

C86100nF

Low ESL

C83

100nF

Low ESL

C88100nF

Low ESL

C77100nF

Low ESL

C67100nF

GND

C902u2FGND

C132u2F

L430nH

L330nH

C56150pF

FB1

330R

UB 1

GND 2B13

B24NC6

UB

GND

B1

B2

NC

GND 5

T5

BD0810J50100A00

GND 1

GND 2OUT3VCC4

U4

TCXO 20.000MHZ

C9210uF

Sc

he

ma

tics

UM

274

2

30/4

4U

M2

742 R

ev 2

Figure 14. External power amplifier

1

1

2

2

3

3

4

4

D D

C C

B B

A A

93_RF_OUT

GND

PA_OUT

R100R

R200R

C104

0.47uF

GND

VPA

GND

C160.47uF

VPA

GN

DG

1

GN

DG

2

I O

J6COAX JACK

GN

DG

1

GN

DG

2

I O

J1COAX JACK

GND

C1052u2F

GND

GND

93_intPA

GND

PA_SW_V2

RFIN1

/SHDN2

GND3

CLPF4 GND 5NC 6

OUT 7VCC 8RFIN

/SHDN

GND

CLPF GND

NC

OUT

VCCU3

Log Detect

GND GND

GNDGND

C152u2F

C70120pF

3V3

Detector

GND

R2251.1R

RF_Detector

TX

EXT_PA_BIAS

GND

PA_SW_V1RF16

RF24

GND5V1 1

RFC 2

V2 3

RF1

RF2

GNDV1

RFC

V2EP7

S1

SP2T

R2562R

R4562R

R24

249R

LP_Filter_IN

LP_Filter_OUT

C108

82pF

C10782pF

C109

82pF

R21

100R

C172n2F

R23

52.3R

NC

2N

C6

IN8 OUT 4

NC

NC

IN OUT

GN

D1

GN

D7

GN

D3

GN

D5

T1

LOWPASS FILTER

VB

IAS

1

VC

C2

NC

3

NC

4

NC

6N

C5

NC

9N

C10

NC

8

RFO

UT

7

VP

D2

11

RFI

N13

VP

D1

12E

xpos

ed P

ad14

U2

TQP9107

C2010uF

Input6

Isolated 2Direct 1

Coupled5

GND 3GND4

Input

Isolated

Direct

Coupled

GNDGND

T220 dB Dir Coupler

UM

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42S

chem

atics

UM

2742

Re

v 231

/44

Figure 15. Carrier cancellation circuit

1

1

2

2

3

3

4

4

D D

C C

B B

A A

GND

GND

ETC_1

ET

C_

2

ETC_3

GND

GND

GND

GND

GND

GND GND

RX_P

RX_N

RX_D

ETC_1ETC_2ETC_3

Carrier_Cancellation ETC_3ETC_2ETC_1

MISOMOSI

CLKSPI

CLK

MOSI

MOSI

MO

SI

MOSI

R34

0R

R35100R DNP

CLK

CL

K

CLK

GND

3V3

3V3

3V3

L116n8H

C37

1p6F

GND GND

C182u2F

C53120pF

GNDGND

C872u2F

C95

120pF

GNDGND

C192u2F

C68120pF

GND

RF_neg1

RF_neg2

GN

D3

VDD4

SC

LK5

SE

N6

SD

AT7

RF_pos 8RF_pos 9

GN

D10

RF_neg

RF_neg

GN

D

VDD

SC

LK

SE

N

SD

AT

RF_pos

RF_pos

GN

D

U7

PE64906MLAA-Z RF_

neg

1

RF_

neg

2

GND 3

VD

D4

SCLK5

SEN6SDAT7

RF_

pos

8R

F_po

s9

GND 10

RF_

neg

RF_

neg

GND

VD

D

SCLK

SEN

SDAT

RF_

pos

RF_

pos

GND

U8

PE64906MLAA-Z

RF_

neg

1R

F_ne

g2

GND3

VD

D4

SCLK 5

SEN 6SDAT 7

RF_

pos

8

RF_

pos

9

GND10

RF_

neg

RF_

neg

GND

VD

D

SCLK

SEN

SDAT

RF_

pos

RF_

pos

GND

U6PE64906MLAA-Z

GND

TX TX_RX

GND

GN

DG

1

GN

DG

2

I O

J3COAX JACK

UB1

GND2B1 3

B2 4NC 6

UB

GND

B1

B2

NC

GND5

T6

BD0810J50100A00

Direct 6

Coupled2Input1

Isolated 5

GND3 GND 4

Direct

Coupled

Input

Isolated

GND GND

T4

10dB Dir Coupler

R26110R

L126n2H

Sc

he

ma

tics

UM

274

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32/4

4U

M2

742 R

ev 2

Figure 16. Antenna switch

Figure 17. RF shield

GND

GND

C36

82pF

C3582pF

GND

TX_RX

ANT_SW_V2

ANT_SW_V1 RF1 6

RF2 4

GND 5V11

RFC2

V23

RF1

RF2

GNDV1

RFC

V2EP 7

S2

SP2T

C112

82pF

P5

SMB JACK STR 50OHM EDGE MNT

P4

SMB JACK STR 50OHM EDGE MNT

GND

GND1

GND2

GND3

GND4

GND5

GND6

GND7

GND8

GND9

GND10

GND11

GND12

GND13

GND14

GND15

GND16

GND17

GND18

GND19

GND20

GND21

GND22

GND23

GND24

GND25

GND26

GND27

GND28

SHIELD1

CRS-50.80X38.1

GND

UM

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atics

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Figure 18. USB supply / UART bridge

1

1

2

2

3

3

4

4

D D

C C

B B

A A

GND

GND

R41 27R

R4727R

C10147pF

C10247pF

GND GND

C103100nF

GND

VBUS

GND

3V3OUT

3V3

GND

GND

UART_RTSUART_DTR

UART_TXUART_RX UART

D_CON_N

D_CON_P

D_ESD_N

D_ESD_P

GND

PWR1

D-2

D+3

ID4

Shield6

GND5

P1μUSB 3V3OUT

10

VC

C1

2

CBUS015

GN

D3

VC

CIO

20

RXD1

RTS#19

TXD17

CTS#6

USBDP8

RESET#11

USBDM9

GN

D1

3

GN

D2

1

CBUS114

CBUS27

CBUS316

DTR#18

DSR#4

DCD#5

RI#2

U13FT231XQ-R

GND

R8620R

C961uF

GND

R890R

R60R

GND

UResetLow ESL

C98100nF

VCC1

IO12

IO23

GND4

VCC8

IO17

IO26

GND5

VCC

IO1

IO2

GND

VCC

IO1

IO2

GND

U14USB6B1

D_CMC_N

D_CMC_P

GND

12

P2Header 2H

C991uF

GND

C236u8F

C302u2F

C332u2F

UReset

D21TVS

D20TVS

GND

TX

RX

RTS

DTR

C974u7F

C1004pF

FB7

31 Ohm

1

4

2

3

T8744231091

Sc

he

ma

tics

UM

274

2

34/4

4U

M2

742 R

ev 2

Figure 19. Microcontroller

1

1

2

2

3

3

4

4

D D

C C

B B

A A

MISOMOSI

CLKSPI

IRQEN

NCSADCOADOAD2

93_Signals

IRQ

CLK

MOSIMISO

NCS

EN

OADOAD2

ETC_1ETC_2ETC_3

Carrier_CancellationETC_3ETC_2ETC_1

NCS

MISOMOSI

ETC_1ETC_2ETC_3

IRQEN

GND GND

OSC32_INOSC32_OUT

OSC32_IN OSC32_OUT

VDDA

VDDA

UART

PA_LDO_EN

MCU_LED

extPA_LED

TUNED_LED

SWDIOSWCLK

SWOTDI

JLINK

RF_LED

MCU_LED

extPA_LED

RF_LED

R7 0RR8 0RR9 0RR11 0R

R12 0RR13 0R

D2LED BL

D1LED BL

D3LED BL

D4LED BL

C25100nF

PA_SW_V2CLK

B1

RESET

R43 0R

R38 0RR39 0RR40 0R

R37 0RR36 0R

3V3

PA014PA115

PA216

PA317PA420

PA521PA622

PA723PA841

PA942

PA1043PA1144

PA1245PA1346

PA1449PA1550

PB026PB127

PB228PB355

PB456PB557

PB658

PB759PB861

PB962PB1029

PB1130PB1233

PB1334

PB1435PB1536

PC0 8PC1 9

PC2 10

PC3 11PC4 24

PC5 25PC6 37

PC7 38PC8 39

PC9 40

PC10 51PC11 52

PC12 53PC13 2

PC14-OSC32_IN 3PC15-OSC32_OUT 4

PD2 54

PH0-OSC_IN 5PH1-OSC_OUT 6

NRST 7BOOT0 60

PA0PPPA1PA2PA3PA4PA5PA6PA7PA8PA9PA10PA11PPPA12PA13PA14PA15

PB0PB1PB2PB3PB4PB5PB6PB7PB8PB9PB10PB11PB12PB13PB14PB15

PC0PC1PC2PC3PC4PC5PC6PC7PC8PC9

PC10PC11PC12PC13

PC14-OSC32_INPC15-OSC32_OUT

PD2

PH0-OSC_INPH1-OSC_OUT

NRSTBOOT0

U1ASTM32L476RGT6

VBAT1

VDDUSB 48

VSS 18VSS 31VSS 47VSS 63

VSSA/VREF- 12

VDDA/VREF+13 VDD 19

VDD 32

VDD 64

VBAT

VDDUSB

VSSVSSVSSVSS

VSSA/VR/ EF-

VDDA/VR// EF+VDDVDDVDD

U1BSTM32L476RGT6

3V3

intPA_LED

D5LED BL

intPA_LED

TAG_LEDD6

LED BL

TAG_LED

PLL_LEDD7

LED BL

OSC_LEDD8

LED BL

PLL_LEDOSC_LED

R1610k

R56 0RR57 0R

UART_RTSUART_DTR

UART_TXUART_RX

MUC_RESET_N

R58 0R UART_LOG_TX

Reset

1 2D9

BAT60JFILM

12

D10BAT60JFILM

3V3

B2Boot

3V3

Boot0

Boot0

R61

10k TUNING_LED

D11LED BL

TUNING_LED

NO_RESP_LED

NO_RESP_LED

CRC_ERR_LED

CRC_ERR_LED

MCU

extPA

intPA

TAG

TUNING

TUNED

RF

PLL

OSC

NO_RESP

CRC_ERR

TUNED_LED

GND

ANT1_LEDD16

LED BLANT1

ANT2_LEDD17

LED BLANT2

ANT1_LEDANT2_LED

X1

NX3215SA-32.768K-STD-MUA-14

C94p7F

C104p7F

FB3

1kC262u2F

C80.47uF

C20.47uF

Lo

w E

SL

C27100nF

Lo

w E

SL

C28100nF

Lo

w E

SL

C29100nF

Lo

w E

SL

C31100nF

RF_Detector

Reset

TP5

TP6

TP7

TP8

TP9

TP10

TP11

TP12

TP13

TP14

TP15

TP16

TP17

BZ1Buzzer

GND

PA_SW_V1

ANT_SW_V2

ANT_SW_V1

D12`LED RD

D13`LED RD

D15`LED RD

R66

220

R65

220

R83

220

R82

220

R53

220

R52

220

R18

220

R17

220

R64

220

R51

220

R50

220

R15

220

R14

220

R81220

C1110uF

Plug_Enable

R92 0R

R93 0R

R90 0R

R91 0R

UM

27

42S

chem

atics

UM

2742

Re

v 235

/44

Figure 20. Supply LDOs

1

1

2

2

3

3

4

4

D D

C C

B B

A A

VPA

GND

GND

PA_LDO_EN

GND

VSUP

GND

GND

GNDGND

3V3

GND

R31

10k

R29

10k

R27

10k

3.6V

R4431k6

VBUS

GND GND GND

5V

3.3V

GND GNDGNDGND

C49

0.47uF

C47

0.47uF

C45

0.47uF

C43

0.47uF

C39

0.47uF

C41

0.47uF

EN1

GND2VO 4

ADJ 5EP

0

VI6PG 3

U10LD39100PUR

EN1

GND2VO 4

ADJ 5EP

0

VI6PG 3

U9LD39100PUR

GND

R1

0R

R2

0R

R3

0R

GND

GND

VBUS

6V

R3090.9k

1 2 3

J5 Header3_THMD DNP

1 2 3

J20 Header3_THMD DNP

1 2 3

J21 Header3_THMD DNP

R2835k7

C382u2F C40

2u2F

C422u2F

C442u2F

C462u2F

C482u2F

EN5

GND3VO 1

ADJ 2

EP

0

VI6PG 4

U11LD39200PUR

1

2

3

2472149

J14

DC_Jack

C1066u8F

3V3

C21

1uF

C22

1uF

FB2

31 Ohm

6V

C242u2F

R32

100K

GND

Plug_Enable

GND GND GND GND

Sc

he

ma

tics

UM

274

2

36/4

4U

M2

742 R

ev 2

Figure 21. External interfaces and connections

1

1

2

2

3

3

4

4

D D

C C

B B

A AMISOMOSI

CLKSPI

IRQEN

NCSADC

OADOAD2

93_Signals

ETC_1ETC_2ETC_3

Carrier_Cancellation

SWD

SWDIOSWCLKSWOTDI

JLINK

PA_LDO_EN

3V3

123456

J12

Header6_THMD DNP

MUC_RESET_N

UART_LOG_TXPA_LDO_EN

UART_LOG_TX

GND

OSCO OSCO

123456789

10

P3

TC2050-IDC-FP

TP1

VCOTP2

VCO

D28

TVS

D29

TVS

D30

TVS

D31

TVS

D32

TVS

D23TVS

D24TVS

D25TVS

D26TVS

D27TVS

D22TVS

D34TVS

D35TVS

D36TVS

D37TVS

D38TVS

D33TVS

D52TVS

D45TVS

EXT_PA_BIASTP3

EXT_PA_BIAS

TP4RF_Detector

UARTUART_RTSUART_DTR

UART_TXUART_RX

D48TVS

D49TVS

D50TVS

D47TVS

123

J8

Header3_THMD DNP

123

J15

Header3_THMD DNP

123

J2

Header3_THMD DNP

123

J10

Header3_THMD DNP

123

J13

Header3_THMD DNP

1J4

Header1_THMD - DNP

1J11

Header1_THMD - DNP

1234

J7

Header4_THMD - DNP

R46

220

R42

220

R19

220

R5

220

R4

220

12

J31

DNP

12

J30

DNP

PA_SW_V2

PA_SW_V1

ANT_SW_V2

ANT_SW_V1

UM2742 Rev 2 37/44

UM2742 PCB

43

4 PCB

The ST25RU3993-HPEV board has in total six layers. The dielectric material between all copper layers is FR-4 type. No blind or buried vias are used.

All components and almost all interconnections are on the top layer (Figure 22).

Impedance-controlled RF traces such as singled-ended 50 Ω (CBCPW) and differential 100 Ω traces are located on the top layer. For best ground connection all component ground terminals have a direct connection to the surrounding GND plane. This means that no thermal relief-connection exist.

The RF GND layer directly below the top layer is needed for the 50 Ω and 100 Ω waveguide traces. The spacing between top layer and RF GND layer is relevant for the impedance of the waveguides. RF currents tend to run back to their source directly underneath the waveguides, so it is important that the RF GND layer is solid and uninterrupted especially underneath the RF traces, to provide a direct path for the RF return currents.

The Power layer (Figure 24) is used to distribute the supply voltages through power planes, and only a few traces are on it.

The Routing layer (Figure 25) is used to interconnect the components minimizing cross-talk effects on RF traces.

Table 16. PCB stack

SchemeLayer Dielectric

Name Type Material Th (mm) Material Ɛr

Top overlay Overlay

Top solder Solder mask/Coverlay Surface 0.01016 Solder resist 4.5

Top layer Signal Copper 0.043 -

Dielectric 1 Dielectric Core 0.25 FR-4 (R-1755M) 4.7

RF GND Signal Copper 0.032 -

Dielectric 2 Dielectric Prepreg 0.1 FR-4 (R-1755M) 4.6

Power Signal Copper 0.032 -


GND Signal Copper 0.036 -

Dielectric 4 Dielectric Prepreg 0.1 FR-4 (R-1755M) 4.6

Routing Signal Copper 0.036 -


Bottom GND Signal Copper 0.043 -

Bottom solder Solder mask/Coverlay Surface 0.01016 Solder resist 4.5

Bottom overlay Overlay

PCB UM2742

38/44 UM2742 Rev 2

Figure 22. Top layer layout

UM2742 Rev 2 39/44

UM2742 PCB

43

Figure 23. RF GND layer (L2), GND layer (L4) and bottom layer (L6) layout

PCB UM2742

40/44 UM2742 Rev 2

Figure 24. Power layer (L3) layout

UM2742 Rev 2 41/44

UM2742 PCB

43

Figure 25. Routing layer (L5) layout

Electrical characteristics UM2742

42/44 UM2742 Rev 2

5 Electrical characteristics

Violating the values listed inTable 17 may damage the reader. Correct operation is not guaranteed when operating outside these specifications.

Table 17. Absolute maximum ratings

Operation temperature 0 °C to +55 °C

Storage temperature 30 °C to +85 °C

DC supply voltage +6.5 V

Table 18. DC characteristics (VBUS = 5.0 V, 25 °C)

Symbol Parameter Min Typ Max Unit

VBUS Supply voltage 4.5 5.0 5.5 V

IBUS Supply current 110 119 125

mAIPAext External PA current(1)

1. Default power setting.

735 840 945

IPAint Internal PA current(1) 325 353 385

UM2742 Rev 2 43/44

UM2742 Revision history

43

6 Revision history

Table 19. Document revision history

Date Revision Changes

10-Aug-2020 1 Initial release.

17-Nov-2020 2

Updated Section 1.1: Board features and Section 2.1: RF circuit.

Updated Table 11: Connection of components, Table 13: Supply voltages of analog test points and Table 18: DC characteristics (VBUS = 5.0 V, 25 °C).

UM2742

44/44 UM2742 Rev 2

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Purchasers 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.

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UM2742 User manual - STMicroelectronics

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