AN0002.2: EFM32 and EFR32 Wireless
Gecko Series 2 Hardware Design
Considerations
This application note details hardware design considerations for
EFM32 and EFR32 Wireless Gecko Series 2 devices. For hardware design considerations for EFM32 and EZR32 Wireless
MCU Series 0 and EFM32 and EFR32 Wireless Gecko Series 1
devices, refer to AN0002.0: EFM32 and EZR32 Wireless MCU
Series 0 Hardware Design Considerations and AN0002.1:
EFM32 and EFR32 Wireless MCU Series 1 Hardware Design
Considerations, respectively.
Topics specifically covered are supported power supply configurations, supply filtering
considerations, debug interface connections, and external clock sources.
For more information on hardware design considerations for the radio portion of EFM32
and EFR32 Wireless Gecko Series 2 devices, see AN930.2: EFR32 Series 2 2.4 GHz
Matching Guide, AN933.2: EFR32 Series 2 2.4 GHz Minimal BOM and AN928.2:
EFR32 Series 2 Layout Design Guide.
KEY POINTS
• Decoupling capacitors are crucial to
ensuring the integrity of the device's power
supplies.
• The debug interface consists of two
communication pins (SWCLK and
SWDIO).
• External clock sources must be connected
to the device correctly for proper
operation.
silabs.com | Building a more connected world. Rev. 0.51
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
1. Device Compatibility
This application note supports multiple device families, and some functionality is different depending on the device.
EFR32 Wireless Gecko Series 2 consists of:
• EFR32BG21
• EFR32MG21
• EFR32BG22
• EFR32FG22
• EFR32MG22
EFM32 Series 2 consists of:
• EFM32PG22
Device Compatibility
silabs.com | Building a more connected world. Rev. 0.51 | 2
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
2. Power Supply Overview
2.1 Introduction
Although the EFM32 and EFR32 Wireless Gecko Series 2 devices have very low average current consumption, proper decoupling is
crucial. As for all digital circuits, current is drawn in short pulses corresponding to the clock edges. Particularly when several I/O lines
are switching simultaneously, transient current pulses on the power supply can be in the order of several hundred mA for a few nanoseconds, even though the average current consumption is quite small.
These kinds of transient currents cannot be properly delivered over high impedance power supply lines without introducing considerable noise in the supply voltage. To reduce this noise, decoupling capacitors are employed to supplement the current during these short
transients.
2.2 Decoupling Capacitors
Decoupling capacitors make the current loop between supply, MCU, and ground as short as possible for high frequency transients.
Therefore, all decoupling capacitors should be placed as close as possible to each of their respective power supply pins, ground pins,
and PCB (Printed Circuit Board) ground planes.
All external decoupling capacitors should have a temperature range reflecting the environment in which the application will be used. For
example, a suitable choice might be X5R ceramic capacitors with a change in capacitance of ±15% over the temperature range -55 to
+85 °C (standard temperature range devices) or -55 to +125 °C (extended temperature range devices).
For regulator output capacitors (DECOUPLE, VREGSW, and VREGO, if available), the system designer should pay particular attention
to the characteristics of the capacitor over temperature and bias voltage. Some capacitors (particularly those in smaller packages or
using cheaper dielectrics) can experience a dramatic reduction in capacitance value across temperature or as the DC bias voltage increases. Any change pushing the regulator output capacitance outside the data sheet specified limits may result in output instability on
that supply.
2.3 Power Supply Requirements
An important consideration for all devices is the voltage requirements and dependencies between the power supply pins. The system
designer needs to ensure that these power supply requirements are met, regardless of power configuration or topology. These internal
relationships between the external voltages applied to the various EFM32 and EFR32 supply pins are defined below. Failure to observe
the below constraints can result in damage to the device and/or increased current draw. Refer to the device data sheet for absolute
maximum ratings and additional details regarding relative system voltage constraints.
EFM32 Series 2 Power Supply Requirements
• AVDD and IOVDD — No dependency on each other or any other supply pin
• VREGVDD ≥ DVDD
• DVDD ≥ DECOUPLE
EFR32 Wireless Gecko Series 2 Power Supply Requirements
• AVDD and IOVDD — No dependency on each other or any other supply pin
• VREGVDD ≥ DVDD
• DVDD ≥ DECOUPLE
• PAVDD ≥ RFVDD
Note: To use EFR32 Wireless Gecko Series 2 for MCU only application, connect the radio related pins as follows:
• PAVDD = RFVDD = DVDD
• RF2G4_IO P/N = NC
Note:
• VREGVDD Power Supply Pin is not available on EFR32xG21 devices.
• On the devices having VREGVDD Power Supply Pin, VREGVDD connections are depend on whether or not the DCDC is used. See
the 2.7 DC-DC section for more information on VREGVDD connections.
silabs.com | Building a more connected world. Rev. 0.51 | 3
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
Power Supply Pin Overview
Note that not all supply pins exist on all devices. The table below provides an overview of the available power supply pins.
Table 2.1. Power Supply Pin Overview
Pin Name Product Family Description
AVDD All devices Supply to analog peripherals
DECOUPLE All devices Output of the internal digital LDO and digital logic supply input
IOVDD All devices GPIO supply voltage
VREGVDD All DC-DC-enabled devices Input to the DC-DC converter
VREGSW All DC-DC-enabled devices DC-DC powertrain switching node
VREGVSS All DC-DC-enabled devices DC-DC ground
DVDD All devices Input to the internal digital LDO
RFVDD EFR32 Wireless Gecko Series 2 only Supply to radio analog and HFXO
PAVDD EFR32 Wireless Gecko Series 2 only Supply to radio power amplifier
2.4 DVDD and DECOUPLE
All EFM32 and EFR32 Wireless Gecko Series 2 devices include an internal linear regulator that powers the core and digital logic. The
DECOUPLE pin is the output of the digital LDO, and requires a 1 µF capacitor. For better high frequency noise suppression a 0.1 µF
capacitor can be placed in parallel with the 1 µF capacitor on the DECOUPLE pin.
As mentioned in section 2.2 Decoupling Capacitors, care should be taken in the selection of decoupling capacitors for regulator output,
such as DECOUPLE, to ensure that changes in system temperature and bias voltage do not cause capacitance changes that fall outside of the data sheet specified limits, which could destabilize the regulator output.
EFM32 and EFR32 Wireless Gecko Series 2 DVDD Pin
On EFM32 and EFR32 Wireless Gecko Series 2 devices, the input supply to the digital LDO is the DVDD pin and the DECOUPLE pin
is the output of the LDO. Decoupling of DVDD should include a bulk capacitor of C
and this bulk capacitor should be at least
DVDD
2.2 µF for EFR32xG21 and 2.7 µF for EFM32PG22 and EFR32xG22. For better high frequency noise suppression a 0.1 µF capacitor
(C
with C
) can be placed in parallel with the C
DVDD1
DECOUPLE
to further improve high frequency noise suppression.
capacitor on the DVDD pin. A similar 0.1 μF capacitor may also be added in parallel
DVDD
silabs.com | Building a more connected world. Rev. 0.51 | 4
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
V
Main
Supply
DD
+
–
C
DVDD
C
DVDD1
0.1 µF
DVDD
Digital
LDO
DECOUPLE
C
DEC
1 µF
Digital
Logic
Figure 2.1. DVDD and DECOUPLE on EFM32 and EFR32 Wireless Gecko Series 2 Devices
Note:
• The DECOUPLE pin should not be used to power any external circuitry. Although DECOUPLE is connected to the output of the
internal digital LDO, it is provided solely for the purposes of decoupling this supply and is not intended to power anything other than
the internal digital logic of the device.
• On EFR32xG22 and EFM32PG22, if DVDD is directly connected to the DCDC, then proper decoupling of DVDD should include a
bulk capacitor of 4.7 µF as shown in 3.4 EFM32 and EFR32 Wireless Gecko Series 2 — DCDC Example. This capacitor should be
placed closer to the L
inductor and the VREGSW pin.
DCDC
2.5 IOVDD
The IOVDD pin(s) provide decoupling for all of the GPIO pins on the device. For proper decoupling when powering IOVDD from the
main supply, include a 0.1 µF capacitor per IOVDD pin, along with a 1 µF bulk capacitor. Increase the bulk capacitor value in applications using GPIO to drive heavy and dynamic loads.
V
Main
Supply
DD
+
–
C
IOVDD_n
0.1 µF
IOVDD_n
. . .
IOVDD_0
C
IOVDD
1 µF
Figure 2.2. IOVDD Decoupling from Main Supply
IOVDD can optionally be driven by the output of the DC-DC converter when present on a device. This is primarily used when connecting to external devices with different operating voltages than the microcontroller. When powering IOVDD from the output of the DC-DC
converter, the bulk 1 µF capacitor is not required, and the DC-DC output should be decoupled by a bulk 4.7 µF capacitor.
Note: When powering IOVDD from the output of the DC-DC converter, the debug interface must connect the V
not the main supply. See the 4. Debug Interface and External Reset Pin section for information on the V
C
IOVDD_0
0.1 µF
target
pin.
pin to IOVDD, and
target
silabs.com | Building a more connected world. Rev. 0.51 | 5
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
2.6 AVDD
The analog peripheral performance of the device is impacted by the quality of the AVDD power supply. For applications with less demanding analog performance, a simpler decoupling scheme for AVDD may be acceptable. For applications requiring the highest quality
analog performance, more robust decoupling and filtering is required.
Note that the number of AVDD analog power pins may vary by device and package.
2.6.1 AVDD Standard Decoupling
The figure below illustrates a standard approach for decoupling the AVDD pin(s). In general, one 1 µF bulk capacitor (C
as one 10 nF capacitor for each AVDD pin (C
Main
Supply
AVDD_0
through C
V
DD
+
–
), must be provided.
AVDD_n
C
10 nF
AVDD_n
AVDD_n
. . .
AVDD
), as well
AVDD_0
C
AVDD
1 µF
Figure 2.3. AVDD Standard Decoupling
2.6.2 AVDD Improved Decoupling
The figure below illustrates an improved approach for decoupling and filtering the AVDD pin(s). In general, one 1 µF bulk capacitor
(C
), as well as one 10 nF capacitor for each AVDD pin (C
AVDD
and series 1 Ω resistor provide additional power supply filtering and isolation and is preferred when higher ADC accuracy is required.
AVDD_0
C
AVDD_0
10 nF
through C
), must be provided. In addition, a ferrite bead
AVDD_n
Main
Supply
V
DD
+
–
FB
VDD
R
AVDD
1 Ω
C
AVDD_n
10 nF
AVDD_n
. . .
AVDD_0
C
AVDD
1 µF
Figure 2.4. AVDD Improved Decoupling
Note: AVDD can be driven by the output of the DC-DC converter when present on a device, so long as analog peripheral inputs are
limited to the lower of AVDD and IOVDD. For example, in a system with 3.3 V digital I/O, the current draw of analog peripherals, such
as the IADC, can be reduced by allowing the DC-DC converter to supply AVDD with and limiting the analog inputs to 1.8 V.
silabs.com | Building a more connected world. Rev. 0.51 | 6
C
AVDD_0
10 nF
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
The table below lists some recommended ferrite bead part numbers suitable for AVDD filtering.
Table 2.2. Recommended Ferrite Beads
Power Supply Overview
Manufacturer Part Number Impedance I
(mA) DCR (Ω) Operating Tempera-
MAX
Package
ture (°C)
Würth Elec-
74279266 1 kΩ @ 100 MHz 200 0.600 -55 to +125 0603/1608
tronics
Würth Elec-
742692004 240 Ω@ 100 MHz 200 0.750 -55 to +125 0201/0603
tronics
Murata BLM21BD102SN1D 1 kΩ @ 100 MHz 200 0.400 -55 to +125 0805/2012
2.7 DC-DC
Some EFM32 and EFR32 Wireless Gecko Series 2 devices provide an on-chip DC-DC converter that can be used for improved power
efficiency. However, the additional switching noise present on the DC-DC converter output (V
), necessitates the use of specific
DCDC
filtering components.
2.7.1 DC-DC — Unused
When the DC-DC converter is not used, the DVDD pin should be shorted to the VREGVDD pin. VREGSW must be left floating, and
VREGVSS should be grounded.
Bypass
Switch
Main
Supply
V
DD
+
–
C
VDD
10 µF
C
VDD1
0.1 µF
VREGVDD
VREGSW
DC-DC
Driver
VREGVSS
DC-DC
DVDD
C
DVDD
C
DVDD1
0.1 µF
Figure 2.5. Configuration when the DC-DC converter is unused
silabs.com | Building a more connected world. Rev. 0.51 | 7
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
2.7.2 DC-DC — Powering DVDD
For the lowest power applications, the DC-DC converter can be used to power the DVDD supply (as well as RFVDD and PAVDD on
EFR32 Wireless Gecko Series 1) as shown in the figure below. In this configuration, the DC-DC Output (V
In addition to being the DC-DC converter feedback path, the DVDD pin powers the internal digital LDO, which in turn powers the digital
circuits.
) is connected to DVDD.
DCDC
The system designer should pay particular attention to the characteristics of the DC-DC output capacitor (C
bias voltage. Some capacitors, particularly those in smaller packages or using cheaper dielectrics, can experience a dramatic reduction
in nominal capacitance in response to temperature changes or as the DC bias voltage increases. Any change pushing the DC-DC output capacitance outside the data sheet specified limits may result in output instability on that supply.
V
DD
Main
Supply
V
+
–
DCDC
10 µF
C
VDD
L
DCDC
2.2 µH
C
DCDC
4.7 µF
C
VDD1
0.1 µF
VREGVDD
VREGSW
VREGVSS
DC-DC
Driver
Bypass
Switch
OFF
DC-DC
) over temperature and
DCDC
DVDD
C
DVDD
0.1 µF
Figure 2.6. DC-DC Converter Powering DVDD
Note: For some Series 2 devices, there are additional DC-DC operating limits which should be observed for performance and reliability.
Refer to the device data sheet for additional details.
2.8 Radio (RFVDD & PAVDD) — EFR32 Wireless Gecko Series 2
On EFR32xG21 devices, the recommended configuration for the radio power supplies (PAVDD and RFVDD) is as follows:
• Connect both PAVDD and RFVDD to the main supply. This configuration supports transmit power up to 20 dBm.
On EFR32xG22 devices, the radio power supplies (PAVDD and RFVDD) are typically powered from one of two sources:
1. The integrated DC-DC converter. This option provides improved power efficiency and supports up to 6 dBm transmit power.
2. The main supply. This option is less efficient and supports up to 6 dBm transmit power.
silabs.com | Building a more connected world. Rev. 0.51 | 8
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Power Supply Overview
2.8.1 RFVDD and PAVDD — Powered from Main Supply
PAVDD and RFVDD can be powered directly from the main supply on EFR32 Wireless Gecko Series 2 devices. The component values
for each device can be found in the Table 2.4 RFVDD & PAVDD Decoupling Values on page 9
L
V
DD
Main
Supply
Figure 2.7. RFVDD and PAVDD Decoupling (2.4 GHz application, both supplies powered from main supply)
+
–
Table 2.3. RFVDD & PAVDD Decoupling Values
RFVDD
L
PAVDD
C
RFVDD
C
PAVDD
C
RFVDD1
C
PAVDD1
RFVDD
PAVDD
RF
Analog
RF
Power
Amplifier
Device Application L
EFR32xG21 2.4 GHz 9.1 nH 47 nF 12 pF 9.1 nH 47 nF 12 pF
EFR32xG22 Ferrite bead
2.8.2 RFVDD and PAVDD — Powered from DCDC
On EFR32xG22 devices, improved power efficiency is achieved using the on-chip DC-DC converter to supply RFVDD and PAVDD.
Figure 2.8. RFVDD and PAVDD Decoupling (2.4 GHz application, both supplies powered from DC-DC converter output)
RFVDD
(BLM15AG102
SN1 or similar)
V
DCDC
C
RFVDD
100 nF 120 pF Ferrite bead
L
RFVDD
C
RFVDD
L
PAVDD
C
PAVDD
C
RFVDD1
C
RFVDD1
C
PAVDD1
RFVDD
PAVDD
L
PAVDD
(BLM15AG102
SN1 or similar)
RF
Analog
RF
Power
Amplifier
C
PAVDD
100 nF 120 pF
C
PAVDD1
Table 2.4. RFVDD & PAVDD Decoupling Values
Device Application L
EFR32xG21 2.4 GHz 9.1 nH 47 nF 12 pF 9.1 nH 47 nF 12 pF
EFR32xG22 Ferrite bead
silabs.com | Building a more connected world. Rev. 0.51 | 9
RFVDD
(BLM15AG102
SN1 or similar)
C
RFVDD
100 nF 120 pF Ferrite bead
C
RFVDD1
L
PAVDD
(BLM15AG102
SN1 or similar)
C
PAVDD
100 nF 120 pF
C
PAVDD1
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Example Power Supply Configurations
3. Example Power Supply Configurations
3.1 EFM32 and EFR32 Wireless Gecko Series 2 — Standard Decoupling Example
The figure below illustrates a standard approach for decoupling an EFM32 and EFR32 Wireless Gecko Series 2 device. The component values for RFVDD and PAVDD for each EFR32 Wireless Gecko Series 2 and application can be found in the 2.8 Radio (RFVDD &
PAVDD) — EFR32 Wireless Gecko Series 2 section. Refer to 2.4 DVDD and DECOUPLE section for C
V
DD
Main
+
Supply
–
C
AVDD
C
AVDD1
10 µF 10 nF
C
IOVDD
1 µF
C
IOVDD1
0.1 µF
component value.
DVDD
C
DVDD
C
DEC
1 µF
C
DVDD1
0.1 µF
DVDD
Digital
LDO
DECOUPLE
FLASH
Digital
L
RFVDD
AVDD
Logic
RFVDD
C
RFVDD
Analog
Blocks
RF
Analog
C
IOVDD
RFVDD1
Power
Amplifier
PAVDD
RF
RFVSS
C
PAVDD1
VSS
L
C
PAVDD
PAVDD
Figure 3.1. EFM32 and EFR32 Wireless Gecko Series 2 Standard Decoupling Example
Note: RF Analog (RFVDD) and RF Power Amplifier (PAVDD) blocks are only available on EFR32 Wireless Gecko Series 2. The figure
above shows the PAVDD supply filtering circuit for 2.4 GHz applications.
Table 3.1. C
Device C
Component Values
DVDD
DVDD
C
DVDD1
EFR32xG21 2.2 µF 0.1 µF
EFR32xG22 2.7 µF 0.1 µF
EFM32PG22 2.7 µF 0.1 µF
Table 3.2. RFVDD & PAVDD Decoupling Values
Device Application L
RFVDD
C
RFVDD
C
RFVDD1
L
PAVDD
C
PAVDD
C
PAVDD1
EFR32xG21 2.4 GHz 9.1 nH 47 nF 12 pF 9.1 nH 47 nF 12 pF
EFR32xG22 Ferrite bead
(BLM15AG102
SN1 or similar)
silabs.com | Building a more connected world. Rev. 0.51 | 10
100 nF 120 pF Ferrite bead
(BLM15AG102
SN1 or similar)
100 nF 120 pF
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Example Power Supply Configurations
3.2 EFM32 and EFR32 Wireless Gecko Series 2 — Improved AVDD Filtering Example
In the following figure, a decoupling approach providing better noise suppression and isolation between the digital and analog power
pins using a ferrite bead and a resistor is illustrated. This configuration is preferred when higher ADC accuracy is required. Refer to
Table 2.2 Recommended Ferrite Beads on page 7 for recommended ferrite bead part numbers.
V
DD
C
Main
Supply
FB
AVDD
R
+
–
AVDD
1 Ω
C
C
AVDD
AVDD1
10 µF 10 nF
C
1 µF
IOVDD
IOVDD1
0.1 µF
C
DVDD
C
DEC
1 µF
C
DVDD1
0.1 µF
DVDD
Digital
LDO
DECOUPLE
FLASH
Digital
L
RFVDD
AVDD
Logic
RFVDD
C
RFVDD
Analog
Blocks
RF
Analog
C
IOVDD
RFVDD1
Power
Amplifier
PAVDD
RF
RFVSS
C
PAVDD1
VSS
C
L
PAVDD
PAVDD
Figure 3.2. EFM32 and EFR32 Wireless Gecko Series 2 Improved AVDD Filtering Example
Note: Note that during power-on for EFM32 and EFR32 Wireless Gecko Series 2 devices, the AVDD_x pins must not be powered up
after the IOVDD_x and DVDD pins. If the rise time of the power supply is short, the filter in the figure above can cause a significant
delay on the AVDD_x pins.
Note: RF Analog (RFVDD) and RF Power Amplifier (PAVDD) blocks are only available on EFR32 Wireless Gecko Series 2. The figure
above shows the PAVDD supply filtering circuit for 2.4 GHz applications.
Table 3.3. C
Device C
Component Values
DVDD
DVDD
C
DVDD1
EFR32xG21 2.2 µF 0.1 µF
EFR32xG22 2.7 µF 0.1 µF
EFM32PG22 2.7 µF 0.1 µF
silabs.com | Building a more connected world. Rev. 0.51 | 11
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Table 3.4. RFVDD & PAVDD Decoupling Values
Example Power Supply Configurations
Device Application L
RFVDD
C
RFVDD
C
RFVDD1
L
PAVDD
C
PAVDD
C
PAVDD1
EFR32xG21 2.4 GHz 9.1 nH 47 nF 12 pF 9.1 nH 47 nF 12 pF
EFR32xG22 Ferrite bead
(BLM15AG102
SN1 or similar)
100 nF 120 pF Ferrite bead
(BLM15AG102
SN1 or similar)
100 nF 120 pF
silabs.com | Building a more connected world. Rev. 0.51 | 12
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Example Power Supply Configurations
3.3 EFM32 and EFR32 Wireless Gecko Series 2 — No DCDC Example
For space or cost-sensitive applications or when power efficiency is not a factor, the DC-DC converter may be left unused. In this configuration:
• The DVDD pin must be shorted to VREGVDD
• In addition, AVDD, IOVDD, RFVDD, and PAVDD are all connected to the main supply.
• VREGSW should be left disconnected.
V
DD
Main
Supply
+
–
C
VDD
10 μF
C
VDD1
0.1 μF
VREGVDD
VREGSW
DC-DC
Driver
C
AVDD
1 μF
Bypass
Switch
C
AVDD1
10 nF
C
IOVDD
1 μF
AVDD
Analog Blocks
C
IOVDD1
0.1 μF
IOVDD
DC-DC
VREGVSS
Analog
Infrastructure
C
DVDD
0.1 μF
C
DEC
1 μF
DVDD
Digital
LDO
DECOUPLE
Digital
Logic
Flash /
HV Digital
RFVDD
RF
Analog
Amplifier
PAVDD
RF
Power
L
PAVDD
L
RFVDD
C
RFVDD
C
RFVDD1
C
PAVDD
C
PAVDD1
Figure 3.3. EFM32 and EFR32 Wireless Gecko Series 2 No DC-DC
Note: RF Analog (RFVDD) and RF Power Amplifier (PAVDD) blocks are only available on EFR32 Wireless Gecko Series 2. The figure
above shows the PAVDD supply filtering circuit for 2.4 GHz applications.
Table 3.5. RFVDD & PAVDD Decoupling Values
Device Application L
RFVDD
C
RFVDD
C
RFVDD1
L
PAVDD
C
PAVDD
C
PAVDD1
EFR32xG21 2.4 GHz 9.1 nH 47 nF 12 pF 9.1 nH 47 nF 12 pF
EFR32xG22 Ferrite bead
(BLM15AG102
SN1 or similar)
100 nF 120 pF Ferrite bead
(BLM15AG102
SN1 or similar)
100 nF 120 pF
silabs.com | Building a more connected world. Rev. 0.51 | 13
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Example Power Supply Configurations
3.4 EFM32 and EFR32 Wireless Gecko Series 2 — DCDC Example
EFM32 and EFR32 Wireless Gecko Series 2 applications should use the DC-DC converter to maximize power savings when it is
present on a device. When the DC-DC converter is used, supply voltages up to 3.3 V are supported without restriction. For supply voltages between 3.3 V and 3.8 V, see the device data sheet. The DC-DC converter requires an external inductor and capacitor, in addition to the standard decoupling capacitors on each power net. For detailed information on the DC-DC converter operation, emlib programming, recommended DC-DC components, and supported power configurations, see application note AN0948: Power Configura-
tions and DC-DC.
For the lowest power radio applications, use the DC-DC converter to supply DVDD, as well as RFVDD and PAVDD. In this configuration:
• The DC-DC output (V
) is connected to DVDD, which powers the internal digital LDO
DCDC
• Both radio power supplies (RFVDD and PAVDD) are also powered from the DC-DC output.
• AVDD and IOVDD are connected to the main supply to support higher voltage external interfaces.
V
DD
Main
Supply
V
DCDC
+
–
C
VDD
10 μF
C
VDD1
0.1 μF
C
VREGVDD
L
DCDC
C
DCDC
4.7 μF
2.2 μH
VREGSW
DC-DC
Driver
VREGVSS
AVDD
1 μF
Bypass
Switch
OFF
DC-DC
C
10 nF
AVDD1
C
1 μF
AVDD
Analog Blocks
Analog
IOVDD
Infrastructure
C
0.1 μF
C
DEC
1 μF
DVDD
DVDD
Digital
LDO
DECOUPLE
Digital
Logic
Flash /
HV Digital
RF
Analog
RFVDD
C
0.1 μF
PAVDD
IOVDD1
IOVDD
RF
Power
Amplifier
BLM18AG102SN1
L
RFVDD
C
RFVDD
100 nF
BLM18AG102SN1
L
PAVDD
C
RFVDD1
120 pF
C
PAVDD
100 nF
C
PAVDD1
120 pF
Figure 3.4. EFR32xG22 Example 2.4 GHz DCDC Power Configuration
Note: The component values shown in this figure are for 2.4 GHz operation on EFR32xG22. For other configurations the component
values for RFVDD and PAVDD supply filtering will change. See the Radio (RFVDD & PAVDD) section for details.
silabs.com | Building a more connected world. Rev. 0.51 | 14
V
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Example Power Supply Configurations
DD
Main
Supply
V
DCDC
+
–
C
VDD
10 μF
C
VDD1
0.1 μF
C
AVDD
1 μF
VREGVDD
Bypass
Switch
OFF
DC-DC
2.2 μH
C
DCDC
4.7 μF
L
DCDC
VREGSW
DC-DC
Driver
VREGVSS
C
AVDD1
10 nF
C
1 μF
AVDD
Analog Blocks
Analog
IOVDD
C
IOVDD1
0.1 μF
IOVDD
Infrastructure
C
0.1 μF
C
DEC
1 μF
DVDD
DVDD
Digital
LDO
DECOUPLE
Digital
Logic
Flash /
HV Digital
Figure 3.5. EFM32PG22 Example DCDC Power Configuration
silabs.com | Building a more connected world. Rev. 0.51 | 15
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Debug Interface and External Reset Pin
4. Debug Interface and External Reset Pin
4.1 Serial Wire Debug
The Serial Wire Debug (SWD) interface is supported by all EFM32 and EFR32 Wireless Gecko Series 2 devices and consists of the
SWCLK (clock input) and SWDIO (data in/out) lines, in addition to the optional SWO/SWV (serial wire output/serial wire viewer). The
SWO/SWV line is used for instrumentation trace and program counter sampling, and is not needed for flash programming and normal
debugging. However, it can be valuable in advanced debugging scenarios, and designers are strongly encouraged to include this along
with the other SWD signals.
Connections to the standard ARM 20-pin debug header are shown in the following figure. Pins that are not connected to the microcontroller, power supply, or ground should be left unconnected.
Gecko Device
Figure 4.1. EFM32 and EFR32 Wireless Gecko Series 2 SWD Connection to the ARM 20-pin Debug Header
Note: The V
is powered by the DC-DC output, V
connection does not supply power. The debugger uses V
target
VMCU
VDD
PA02
PA01
PA03
RESETn
VSS
SWDIO
SWCLK
SWO/SWV
Reset
ARM 20 Pin Header
as a reference voltage for its level translators. If IOVDD
target
should be connected to IOVDD, not the main supply.
target
VMCU
Vtarget
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
For additional debug and programming interfaces, see Application Note AN958: Debugging and Programming Interfaces for Custom
Designs.
silabs.com | Building a more connected world. Rev. 0.51 | 16
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Debug Interface and External Reset Pin
4.2 JTAG Debug
EFM32 and EFR32 Wireless Gecko Series 2 devices optionally support JTAG debug using the TCK (clock), TDI (data input), TDO (data output), and TMS (input mode select) lines. TCK is the JTAG interface clock. TDI carries input data and is sampled on the rising
edge of TCK. TDO carries output data and is shifted out on the falling edge of TCK. Finally, TMS is the input mode select signal, and is
used to navigate through the Test Access Port (TAP) state machine.
Note: The JTAG implementation on EFM32 and EFR32 Wireless Gecko Series 2 devices does not support boundary scan testing. It
can operate in pass-through mode and participate in a chain with other devices that do implement JTAG for firmware programming or
boundary scan purposes.
The connection to an ARM 20-pin debug connector is shown in the following figure. Pins with no connection should be left unconnected.
VMCU
IOVDD
PA04
PA02
PA01
PA03
RESETn
Gecko Device
TDI
TMS
TCK
TDO
Reset
VSS
VMCU
Vtarget
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
ARM 20 Pin Header
Figure 4.2. EFM32 and EFR32 Wireless Gecko Series 2 JTAG Connection to the ARM 20-pin Debug Header
Note: The V
For additional debug and programming interfaces, see Application Note AN958: Debugging and Programming Interfaces for Custom
Designs.
connection does not supply power. The debugger uses V
target
as a reference voltage for its level translators.
target
4.3 External Reset Pin (RESETn)
EFM32 and EFR32 Wireless Gecko Series 2 processors are reset by driving the RESETn pin low. A weak internal pull-up device holds
the RESETn pin high, allowing it to be left unconnected if no external reset source is required. Also connected to RESETn is a low-pass
filter to prevents noise glitches from causing unintended resets. The characteristics of the pull-up device and input filter are identical to
those present on any GPIO pin and are specified in the device data sheet.
Note:
1. The internal pull-up ensures that the reset is released. When the device is not powered, RESETn must not be connected through
an external pull-up to an active supply or otherwise driven high as this could damage the device.
2. The RESETn pin is pulled up internally to DVDD. In the case where RESETn is connected to an external signal capable of driving
the pin at a voltage different from V
, this internal pull up represents a possible current path, which could cause unwanted pow-
DVDD
er consumption. Examples include connection of RESETn to an external supply/reset monitor, debugger, or coprocessor/multi-chip
design. It is recommended that if RESETn is connected to an external device, it be connected only to open drain signals in order to
avoid unwanted current consumption when RESETn is not being driven low.
3. External drivers for RESETn should be configured as open drain and not push / pull, especially for designs where the driver source
is at a different potential from the main supply.
silabs.com | Building a more connected world. Rev. 0.51 | 17
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
External Clock Sources
5. External Clock Sources
5.1 Introduction
EFM32 and EFR32 Wireless Gecko Series 2 devices support different external clock sources to provide the high- and low-frequency
clocks in addition to the internal LF and HF RC oscillators. Possible external clock sources for both the LF and HF domains are crystals
and external oscillators (square or sine wave). This section describes how external clock sources are connected.
For additional information on the external oscillators, refer to the application note, AN0016.2: Oscillator DesignConsiderations . Application notes can be found on the Silicon Labs website (www.silabs.com/32bit-appnotes) or in Simplicity Studio.
5.2 Low-Frequency Clock Sources
An external low-frequency clock can be supplied from a crystal or from an external clock source.
5.2.1 Low-Frequency Crystals
A crystal is connected as shown in the figure below across the LFXTAL_I and LFXTAL_O pins on EFM32 and EFR32 Wireless Gecko
Series 2 devices.
LFXTAL_I
C
C
TUNING
TUNING
32.768 kHz
LFXTAL_O
Gecko Device
Figure 5.1. Low-Frequency Crystal Oscillator
Low frequency crystals connected to EFM32 and EFR32 Wireless Gecko Series 2 devices do not require external load capacitors, as
these load capacitors are included on-chip and can be tuned by register bit fields under software control, thus reducing BOM cost and
saving space in the PCB footprint. The EFM32 and EFR32 Wireless Gecko Series 2 LFXO supports 32.768 kHz crystals. Check device-specific data sheets for supported crystal load capacitance and ESR values and refer to device-specific reference manuals for onchip load capacitor tuning instructions.
silabs.com | Building a more connected world. Rev. 0.51 | 18
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
External Clock Sources
5.2.2 Low-Frequency External Clocks
EFM32 and EFR32 Wireless Gecko Series 2 devices can source a low-frequency clock from an external source such as a TCXO or
VCXO. To select a proper external oscillator, consider specifications such as frequency, aging, stability, voltage sensitivity, rise and fall
time, duty cycle, and signal levels. The external clock signal can be either a square wave or a sine wave with a frequency of 32.768
kHz. The external clock source must be connected as shown in Figure 5.2 Low-Frequency External Clock on page 19.
Bypass and buffered input modes are supported for external clock sources. A CMOS square wave that toggles between 0 and V
IOVDD
volts with a duty cycle of 50% can be used when LFXO_CFG_MODE = DIGEXTCLK, which bypasses the LFXO. An external sine wave
source (LFXO_CFG_MODE = BUFEXTCLK) having minimum and maximum amplitudes of 100 mV and 500 mV, respectively, can be
connected in series with the LFXTAL_I pin and is AC-coupled internally. The sine wave minimum voltage must be higher than ground
and the maximum voltage less than V
. When using either DIGEXTCLK or BUFEXTCLK mode, the LFXTAL_O pin is free to be
IOVDD
used as a general purpose GPIO.
External
32.768 kHz
Clock Source
LFXTAL_I
LFXTAL_O
Gecko Device
Figure 5.2. Low-Frequency External Clock
5.3 High Frequency Clock Sources
An external high-frequency clock can be supplied from a crystal or from an external clock source.
5.3.1 High-Frequency Crystals
A crystal is connected as shown in Figure 5.3 High-Frequency Crystal Oscillator on page 19 across the HFXTAL_I and HFXTAL_O
pins on EFM32 and EFR32 Wireless Gecko Series 2 devices.
External load capacitors are not required on EFM32 and EFR32 Wireless Gecko Series 2 devices. These have been moved on-chip
and can be tuned by register bit fields under software control, thus reducing BOM cost and saving space in the PCB footprint. Check
device-specific data sheets for the supported range of crystal frequencies, load capacitance tuning, and ESR values. In particular, specific crystal frequencies are mandatory when using on-chip radios and their associated protocol stacks; use of other values is expressly
not supported.
HFXTAL_I
C
C
TUNING
TUNING
38 – 40 MHz
HFXTAL_O
Gecko Device
Figure 5.3. High-Frequency Crystal Oscillator
silabs.com | Building a more connected world. Rev. 0.51 | 19
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
External Clock Sources
5.3.2 High-Frequency External Clocks
EFM32 and EFR32 Wireless Gecko Series 2 devices can source a low-frequency clock from an external source such as a TCXO or
VCXO. To select a proper external oscillator, consider specifications such as frequency, aging, stability, voltage sensitivity, rise and fall
time, duty cycle, and signal levels. The external clock signal can be either a square wave or a sine wave with a frequency in accordance with the device data sheet. The external clock source must be connected as shown in Figure 5.4 High-Frequency External Clock
on page 20.
Unlike the LFXO, which has specific modes for a buffered or digital external clock, the HFXO has more limited external clock input flexibility. When a crystal is not used, the external clock signal must be a sine wave (HFXO_CFG_MODE = EXTCLK) having minimum and
maximum amplitudes of 100 mV and 500 mV, respectively, can be connected in series with the HFXTAL_I pin and is AC-coupled internally. The sine wave minimum voltage must be higher than ground and the maximum voltage less than 1.4 V.
External
Clock Source
HFXTAL_I
HFXTAL_O
Gecko Device
Figure 5.4. High-Frequency External Clock
silabs.com | Building a more connected world. Rev. 0.51 | 20
AN0002.2: EFM32 and EFR32 Wireless Gecko Series 2 Hardware Design Considerations
Revision History
6. Revision History
Revision 0.51
January, 2021
• Updated Device Compatibility to add support for EFM32PG22.
• Update Power Supply and Example Power Supply Configurations sections to add EFM32PG22 support.
• Added new notes in 2.3 Power Supply Requirements section to provide clarity.
• Update the document throughout to include EFM32 support.
• Improved clarity of figures and descriptions throughout.
• Added recommendation to configure external RESETn drivers as open-drain.
Revision 0.5
June, 2020
• Added required amplitude of a sine wave oscillator input in 5.2.2 Low-Frequency External Clocks and 5.3.2 High-Frequency External
Clocks.
Revision 0.4
April, 2020
• Added information about EFR32xG22 in 2.4 DVDD and DECOUPLE, 2.5 IOVDD and 2.6 AVDD sections.
• Added reference to 2.4 DVDD and DECOUPLE section for C
value in 3.1 EFM32 and EFR32 Wireless Gecko Series 2 —
DVDD
Standard Decoupling Example and 3.1 EFM32 and EFR32 Wireless Gecko Series 2 — Standard Decoupling Example sections.
• Updated C
value in 3.3 EFM32 and EFR32 Wireless Gecko Series 2 — No DCDC Example and 3.4 EFM32 and EFR32 Wire-
IOVDD
less Gecko Series 2 — DCDC Example sections.
Revision 0.3
March, 2020
• Added reference to AN933.2 in the front page.
• Updated Device Compatibility to add support for EFR32xG22.
• Added 2.7 DC-DC to add support for EFR32xG22.
• Added information regarding powering RFVDD and PAVDD from Main Supply and DC-DC converter output in 2.8 Radio (RFVDD &
PAVDD) — EFR32 Wireless Gecko Series 2.
• Added information about EFR32xG22 in 3. Example Power Supply Configurations.
• Removed references to ceramic resonator in 5. External Clock Sources.
• Removed references to external square wave source in 5.3 High Frequency Clock Sources.
Revision 0.2
December, 2019
• Added reference to AN958 in 4.1 Serial Wire Debug and 4.2 JTAG Debug.
Revision 0.1
February, 2019
• Initial revision.
silabs.com | Building a more connected world. Rev. 0.51 | 21
Simplicity Studio
One-click access to MCU and wireless
tools, documentation, software, source
code libraries & more. Available for
Windows, Mac and Linux!
IoT Portfolio
www.silabs.com/IoT
Disclaimer
Silicon Labs intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or
intending to use the Silicon Labs products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and “Typical”
parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Labs reserves the right to make changes
without further notice to the product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information.
Without prior notification, Silicon Labs may update product firmware during the manufacturing process for security or reliability reasons. Such changes will not alter the specifications or
the performance of the product. Silicon Labs shall have no liability for the consequences of use of the information supplied in this document. This document does not imply or expressly
grant any license to design or fabricate any integrated circuits. The products are not designed or authorized to be used within any FDA Class III devices, applications for which FDA
premarket approval is required, or Life Support Systems without the specific written consent of Silicon Labs. A “Life Support System” is any product or system intended to support or
sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Labs products are not designed or authorized for military
applications. Silicon Labs products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or
missiles capable of delivering such weapons. Silicon Labs disclaims all express and implied warranties and shall not be responsible or liable for any injuries or damages related to use of
a Silicon Labs product in such unauthorized applications.
Trademark Information
Silicon Laboratories Inc.®, Silicon Laboratories®, Silicon Labs®, SiLabs® and the Silicon Labs logo®, Bluegiga®, Bluegiga Logo®, ClockBuilder®, CMEMS®, DSPLL®, EFM®,
EFM32®, EFR, Ember®, Energy Micro, Energy Micro logo and combinations thereof, “the world’s most energy friendly microcontrollers”, Ember®, EZLink®, EZRadio®, EZRadioPRO®,
Gecko®, Gecko OS, Gecko OS Studio, ISOmodem®, Precision32®, ProSLIC®, Simplicity Studio®, SiPHY®, Telegesis, the Telegesis Logo®, USBXpress®, Zentri, the Zentri logo and
Zentri DMS, Z-Wave®, and others are trademarks or registered trademarks of Silicon Labs. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM
Holdings. Keil is a registered trademark of ARM Limited. Wi-Fi is a registered trademark of the Wi-Fi Alliance. All other products or brand names mentioned herein are trademarks of
their respective holders.
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, T X 78701
USA
http: //www.silabs.com
SW/HW
ww.silabs.com/simplicity
w
Quality
ww.silabs.com/quality
w
Support & Community
abs.com/community
www.sil
Loading...