Silicon Laboratories EFR32MG User manual

EFR32MG 2.4 GHz 19.5 dBm Radio Board

BRD4154A Reference Manual

The EFR32MG family of Wireless SoCs deliver a high perform-

ance, low energy wireless solution integrated into a small form

factor package.

By combining a high performance 2.4 GHz RF transceiver with an energy efficient 32-bit

MCU, the family provides designers the ultimate in flexibility with a family of pin-compati-

ble devices that scale from 128/256 kB of flash and 16/32 kB of RAM. The ultra-low

power operating modes and fast wake-up times of the Silicon Labs energy friendly 32-

bit MCUs, combined with the low transmit and receive power consumption of the 2.4

GHz radio, result in a solution optimized for battery powered applications.

RADIO BOARD FEATURES

• Wireless SoC:

EFR32MG1P732F256GM32

• CPU core: ARM Cortex-M4 with FPU

• Flash memory: 256 kB + 512 kB

• RAM: 32 kB

• Operation frequency: 2.4 GHz

• Transmit power: 19.5 dBm

• Integrated PCB antenna, UFL connector

(optional).

• Crystals for LFXO and HFXO: 32.768 kHz

and 38.4 MHz.

To develop and/or evaluate the EFR32 Mighty Gecko the BRD4154A Radio Board can

be connected to the Wireless Starter Kit Mainboard to get access to display, buttons and

additional features from Expansion Boards.

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1. Introduction

The EFR32 Mighty Gecko Radio Boards provide a development platform (together with the Wireless Starter Kit Mainboard) for the

Silicon Labs EFR32 Mighty Gecko Wireless System on Chips and serve as reference designs for the matching network of the RF inter-

face.

The BRD4154A Radio Board is designed to the operate in the 2400-2483.5 MHz band with the RF matching network optimized to oper-

ate with 19.5 dBm output power.

To develop and/or evaluate the EFR32 Mighty Gecko the BRD4154A Radio Board can be connected to the Wireless Starter Kit Main-

board to get access to display, buttons and additional features from Expansion Boards and also to evaluate the performance of the RF

interface.

BRD4154A Reference Manual

Introduction

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2. Radio Board Connector

2.1 Introduction

The board-to-board connector scheme allows access to all EFR32MG1 GPIO pins as well as the RESETn signal. For more information

on the functions of the available pin functions, we refer you to the EFR32MG1 Datasheet.

2.2 Radio Board Connector Pin Associations

The figure below shows the pin mapping on the connector to the radio pins, to the I/O Expander pins (shown in brackets) and their

function on the Wireless Starter Kit Mainboard.

GND

F9 / PD13 / VCOM.RTS_CS / DISP_SCS

3v3

IOEXP_DBG_C2D / P36

P200

Upper Row

NC / P38

NC / P40

NC / P42

NC / P44

DEBUG.TMS_SWDIO / PF1 / F0

DISP_ENABLE ** / (P1.2) / F14

UIF_BUTTON0 / (P0.0) / PD14 / F12

UIF_LED0 ** / (P1.5) / F10

VCOM.CTS_SCLK / DISP_SCLK / PB11 / F8

DEBUG.RESET / RADIO_#RESET / P4

DEBUG.TDO_SWO / PF2 / F2

VCOM.TX_MOSI / DISP_SI / PA0 / F16

VCOM.TX_MOSI / DISP_SI / PA0 / F6

PTI_DATA / PB12 / F20

DISP_EXTCOMIN ** / (P1.3) / F18

USB_VBUS

Board ID SCL

GND

Board ID SDA

USB_VREG

F7 / PA1 / VCOM.RX_MISO

F5 / (P1.1) / VCOM_ENABLE **

F3 / NC

F1 / PF0 / DEBUG.TCK_SWCLK

P45 / NC

P43 / NC

P41 / NC

P39 / NC

P37 / (P1.0) / SENSOR_ENABLE **

F11 / (P1.6) / UIF_LED1 **

F13 / PD15 / (P0.1) / UIF_BUTTON1

F15 / PB11 / COM.CTS_SCLK / DISP_SCLK

F17 / PD13 / VCOM.RTS_CS / DISP_SCS

F19 / PB13 / PTI_FRAME

F21 / NC

GND VMCU_IN

(P0.6) / PF3 / P0

P201

Lower Row

NC / P2

UIF_BUTTON0 / PD14 / P4

UIF_BUTTON1 / PD15 / P6

GND VRF_IN

P35 / IOEXP_DBG_C2CK

P7 / PD13 / VCOM.RTS_CS / DISP_SCS

P5 / PB11 / VCOM.CTS_SCLK / DISP_SCLK

P3 / PA1 / VCOM.RX_MISO

P1 / PA0 / VCOM.TX_MOSI / DISP_SI

P33 /

P31 /

P29 / PF2 / DEBUG.TDO_SWO

P27 / PF1 / DEBUG.TMS_SWDIO

P25 / PF0 / DEBUG.TCK_SWCLK

P23 / NC

P21 / NC

P19 / NC

P17 / NC

P15 / NC

P13 / PC10 / (P0.4)

P11 / NC

P9 / NC

NC / P34

NC / P32

NC / P30

NC / P28

NC / P26

NC / P24

NC / P22

NC / P20

NC / P18

PTI_FRAME / PB13 / P16

PTI_DATA / PB12 / P14

(P0.5) / PC11 / P12

PB15 * / P10

PB14 * / P8

* Connection is not available by default.

Can be enabled through solderable jumpers. See the schematic of the Radio Board.

** Connection is only available through the on-board I/O expander. The associated I/O expander ports are shown in brackets.

Figure 2.1. BRD4154A Radio Board Connector Pin Mapping

BRD4154A Reference Manual

Radio Board Connector

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3. Radio Board Block Summary

3.1 Introduction

This section gives a short introduction to the blocks of the BRD4154A Radio Board.

3.2 Radio Board Block Diagram

The block diagram of the BRD4154A Radio Board is shown in the figure below.

Inverted-F

PCB

Antenna

2.4 GHz RF

UFL

Connector

Crystal

32.768k

Crystal

38.4M

Radio

Board

Connectors

8 Mbit

MX25R

Serial Flash

I2C

24AA0024

Serial EEPROM

Matching

Network &

Path

Selection

GPIO

UART

Debug

Packet Trace

AEM

I2C

SPI

2.4 GHz RF

EFM8

I/O Expander

I2C

Debug

GPIO

EFR32

Wireless SoC

Figure 3.1. BRD4154A Block Diagram

3.3 Radio Board Block Description

3.3.1 Wireless MCU

The BRD4154A EFR32 Mighty Gecko Radio Board incorporates an EFR32MG1P732F256GM32 Wireless System on Chip featuring

32-bit Cortex-M4 with FPU core, 256 kB + 512 kB of flash memory and 32 kB of RAM and a 2.4 GHz band transceiver with output

power up to 19.5 dBm. For additional information on the EFR32MG1P732F256GM32, refer to the EFR32MG1 Data Sheet.

3.3.2 LF Crystal Oscillator (LFXO)

The BRD4154A Radio Board has a 32.768 kHz crystal mounted.

3.3.3 HF Crystal Oscillator (HFXO)

The BRD4154A Radio Board has a 38.4 MHz crystal mounted.

3.3.4 Matching Network for 2.4 GHz

The BRD4154A Radio Board incorporates a 2.4 GHz matching network which connects the 2.4 GHz TRX pin of the EFR32MG1 to the

one on-board printed Inverted-F antenna. The component values were optimized for the 2.4 GHz band RF performace and current con-

sumption with 19.5 dBm output power.

BRD4154A Reference Manual

Radio Board Block Summary

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For detailed description of the matching network see Chapter 4.2.1 Description of the 2.4 GHz RF Matching.

3.3.5 Inverted-F Antenna

The BRD4154A Radio Board includes a printed Inverted-F antenna (IFA) tuned to have close to 50 Ohm impedance at the 2.4 GHz

band.

For detailed description of the antenna see Chapter 4.5 Inverted-F Antenna.

3.3.6 UFL Connector

To be able to perform conducted measurements Silicon Labs added an UFL connector to the Radio Board. The connector allows an

external 50 Ohm cable or antenna to be connected during design verification or testing.

Note: By default the output of the matching network is connected to the printed Inverted-F antenna by a series component. It can be

connected to the UFL connector as well through a series 0 Ohm resistor which is not mounted by default. For conducted measurements

through the UFL connector the series component to the antenna should be removed and the 0 Ohm resistor should be mounted (see

Chapter 4.2 Schematic of the RF Matching Network for further details).

3.3.7 Radio Board Connectors

Two dual-row, 0.05” pitch polarized connectors make up the BRD4154A Radio Board interface to the Wireless Starter Kit Mainboard.

For more information on the pin mapping between the EFR32MG1P732F256GM32 and the Radio Board Connector refer to Chapter

2.2 Radio Board Connector Pin Associations.

3.3.8 I/O Expander

Due to the I/O port constraint of the EFR32MG1P732F256GM32 the BRD4154A Radio Board has an EFM8 family MCU mounted as an

I/O port expander to be able to utilize additional Wireless Starter Kit Mainboard features (LEDs, display etc.).

For more information on the pin mapping between the I/O Expander and the Radio Board Connector refer to Chapter 2.2 Radio Board

Connector Pin Associations.

BRD4154A Reference Manual

Radio Board Block Summary

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4. RF Section

4.1 Introduction

This section gives a short introduction to the RF section of the BRD4154A.

4.2 Schematic of the RF Matching Network

The schematic of the RF section of the BRD4154A Radio Board is shown in the following figure.

GND

U.FL

Ground

RF I/ORF Crystal

RF Analog Power

PA Power

U1B

EFR32

2G4RF_IOP 17

2G4RF_ION 16

RFVDD

HFXI

HFXO

PAVDD

RFVSS 14

PAVSS 15

L1 AT1

INVERTED_F

Path

Selection

Inverted-F

Antenna

2.4 GHz

Matching

Network

Test

Connector

TRX Matching &

Filter

GND

PAVDD

VDCDC

GND

HFXTAL_P

HFXTAL_N

C107

10P

L102

BLM18AG601SN1

1 2

L103

BLM18AG601SN1

1 2

C102

100P

C103

10P

C106

220N

Supply Filtering

Figure 4.1. Schematic of the RF Section of the BRD4154A

4.2.1 Description of the 2.4 GHz RF Matching

The 2.4 GHz matching connects the 2G4RF_IOP pin to the on-board printed Inverted-F Antenna. The 2G4RF_ION pin is connected to

ground. For higher output powers (13 dBm and above) beside the impedance matching circuitry it is recommended to use additional

harmonic filtering as well at the RF output. The targeted output power of the BRD4154A board is 19.5 dBm thus the RF output of the IC

is connected to the antenna through a four-element impedance matching and harmonic filter circuitry.

For conducted measurements the output of the matching network can also be connected to the UFL connector by relocating the series

R1 resistor (0 Ohm) to the R2 resistor position between the output of the matching and the UFL connector.

4.3 RF Section Power Supply

On the BRD4154A Radio Board the supply pin of the RF Analog Power (RFVDD) is connected directly ot the output of the on-chip DC-

DC converter while the supply for the 2.4 GHz PA (PAVDD) is provided directly by the mainboard. This way, by default, the DC-DC

converter provides 1.8 V for the RF analog section, the mainboard provides 3.3 V for the PA (for details, see the schematic of the

BRD4154A).

4.4 Bill of Materials for the 2.4 GHz Matching

The Bill of Materials of the 2.4 GHz matching network of the BRD4154A Radio Board is shown in the following table.

Table 4.1. Bill of Materials for the BRD4154A 2.4 GHz 19.5 dBm RF Matching Network

Component name Value Manufacturer Part Number

L1 1.8 nH Murata LQP15MN1N8W02

L2 3.0 nH Murata LQP15MN3N0W00

C1 2.0 pF Murata GRM1555C1H2R0WA01

C2 1.0 pF Murata GRM1555C1H1R0WA01

BRD4154A Reference Manual

RF Section

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4.5 Inverted-F Antenna

The BRD4154A Radio Board includes an on-board printed Inverted-F Antenna tuned for the 2.4 GHz band. Due to the design restric-

tions of the Radio Board the input of the antenna and the output of the matching network can't be placed directly next to each other thus

a 50 Ohm transmission line was necessary to connect them. The resulting impedance and reflection measured at the output of the

matcing network are shown in the following figure. As it can be observed the impedance is close to 50 Ohm (the reflection is better than

-10 dB) for the entire 2.4 GHz band.

Figure 4.2. Impedance and Reflection of the Inverted-F Antenna of the BRD4154A

BRD4154A Reference Manual

RF Section

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5. Mechanical Details

The BRD4154A EFR32 Mighty Gecko Radio Board is illustrated in the figures below.

EFR32xx

Frame of

the

Optional

Shielding

Can

45 mm

30 mm

DC-DC

Inductor

DC-DC

Supply

Filter

Caps.

PAVDD Supply

Filtering

Figure 5.1. BRD4154A Top View

24 mm

27.3 mm

28.6 mm

5 mm

Interface

Connector

Interface

Connector

15 mm

Board

Identification

Display

Enable

Selection

Figure 5.2. BRD4154A Bottom View

BRD4154A Reference Manual

Mechanical Details

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6. EMC Compliance

6.1 Introduction

Compliance of the fundamental and harmonic levels is tested against the following standards:

• 2.4 GHz:

• ETSI EN 300-328

• FCC 15.247

6.2 EMC Regulations for 2.4 GHz

6.2.1 ETSI EN 300-328 Emission Limits for the 2400-2483.5 MHz Band

Based on ETSI EN 300-328 the allowed maximum fundamental power for the 2400-2483.5 MHz band is 20 dBm EIRP. For the unwan-

ted emissions in the 1 GHz to 12.75 GHz domain the specified limit is -30 dBm EIRP.

6.2.2 FCC15.247 Emission Limits for the 2400-2483.5 MHz Band

FCC 15.247 allows conducted output power up to 1 Watt (30 dBm) in the 2400-2483.5 MHz band. For spurious emmissions the limit is

-20 dBc based on either conducted or radiated measurement, if the emission is not in a restricted band. The restricted bands are speci-

fied in FCC 15.205. In these bands the spurious emission levels must meet the levels set out in FCC 15.209. In the range from

960 MHz to the frequency of the 5th harmonic it is defined as 0.5 mV/m at 3 m distance (equals to -41.2 dBm in EIRP).

Additionally, for spurious frequencies above 1 GHz FCC 15.35 allows duty-cycle relaxation to the regulatory limits. For the EmberZNet

PRO the relaxation is 3.6 dB. So practically the -41.2 dBm limit can be modified to -37.6 dBm.

In case of operating in the 2400-2483.5 MHz band the 2nd, 3rd and 5th harmonics can fall into restricted bands so for those the

-37.6 dBm limit should be applied. For the 4th harmonic the -20 dBc limit should be applied.

6.2.3 Applied Emission Limits for the 2.4 GHz Band

The above ETSI limits are applied both for conducted and radiated measurements.

The FCC restricted band limits are radiated limits only. Besides that, Silicon Labs applies those to the conducted spectrum i.e. it is as-

sumed that in case of a custom board an antenna is used which has 0 dB gain at the fundamental and the harmonic frequencies. In that

theoretical case, based on the conducted measurement, the compliance with the radiated limits can be estimated.

The overall applied limits are shown in the table below.

Table 6.1. Applied Limits for Spurious Emissions for the 2.4 GHz Band

Harmonic Frequency Limit

2nd 4800~4967 MHz -37.6 dBm

3rd 7200~7450.5 MHz -37.6 dBm

4th 9600~9934 MHz -30 dBm

5th 12000~12417.5 MHz -37.6 dBm

BRD4154A Reference Manual

EMC Compliance

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7. RF Performance

7.1 Conducted Power Measurements

During measurements the BRD4154A Radio Board was attached to a Wireless Starter Kit Mainboard which was supplied by USB. The

voltage supply for the Radio Board was 3.3 V.

7.1.1 Conducted Measurements in the 2.4 GHz band

The BRD4154A board was connected directly to a Spectrum Analyzer through its UFL connector (the R1 resistor (0 Ohm) was removed

and a 0 Ohm resistor was soldered to the R2 resistor position). The supply for the radio (RFVDD) was 1.8 V provided by the on-chip

DC-DC converter, the supply for the power amplifier (PAVDD) was 3.3 V provided by the Motherboard (for details, see the schematic of

the BRD4154A). The transceiver was operated in continuous carrier transmission mode. The output power of the radio was set to 19.5

dBm.

The typical output spectrum is shown in the following figure.

Figure 7.1. Typical Output Spectrum of the BRD4154A

As it can be observed the fundamental is slightly lower than 19.5 dBm and the strongest unwanted emission is the double-frequency

harmonic but with its -56.45 dBm level it is under the -37.6 dBm applied limit with large margin.

Note: The conducted measurement is performed by connecting the on-board UFL connector to a Spectrum Analyzer through an SMA

Conversion Adapter (P/N: HRMJ-U.FLP(40)). This connection itself introduces approx. 0.3 dB insertion loss.

BRD4154A Reference Manual

RF Performance

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