AN0002

AN0002: Hardware Design Considerations
This application note details hardware design considerations for
EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless
Gecko devices.
Topics specifically covered are supported power supply configurations, supply filtering
considerations, debug interface connections, and external clock sources. In addition,
reference designs for the EFM32 Series 1 Gecko microcontrollers are included.
For simplicity, EFM32 Series 1 Gecko is used throughout this document to represent
the EFM32 Wonder Gecko, Gecko, Giant Gecko, Leopard Gecko, Tiny Gecko, Zero
Gecko, or Happy Gecko MCU series, EZR32 is used to represent the EZR32 Wireless
MCUs, EFR32 Wireless Gecko is used to represent the EFR32 Wireless Gecko portfolio devices, and EFM32 Series 2 Gecko is used to represent the EFM32 Pearl Gecko
and Jade Gecko (and future devices).
For more information on hardware design and layout considerations for the DC-DC
converter on EFM32 Series 2 and EFR32 Wireless Gecko devices, see AN0948: Power Configurations and DC-DC.
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.
• This application note includes:
• This PDF document
• Reference Design (zip)
• OrCAD schematic design files
• PDF Schematics
• Symbol libraries (OrCAD, CSV, and
Edif formats)
For more information on hardware layout considerations for the radio portion of EFR32
Wireless Gecko devices, see AN930: EFR32 2.4 GHz Matching Guide, AN933: EFR32
2.4 GHz Minimal BOM, and AN928: EFR32 Layout Design Guide.
For more information on hardware layout considerations for the radio portion of EZR32
devices, see AN629: Si4460/61/63/64/67/68 RF ICs Layout Design Guide.
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AN0002: Hardware Design Considerations
Power Supply Overview
1. Power Supply Overview
1.1 Introduction
Although the EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko devices have an exceptionally small 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.
1.2 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 pin, ground pin, and
PCB (Printed Circuit Board) ground plane.
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 °C
– +85°C (standard temperature range devices) or -55 °C – +125°C (extended temperature range devices).
1.3 Power Supply Pin Overview
Note that not all supply pins exist on all devices. The table below describes the supply pins and where it appears.
Table 1.1. Power Supply Pin Overview
Pin Name
Product Family
Description
VDD_VREG
EFM32 Series 1 Gecko and EZR32
only
Input to the internal Digital LDO
AVDD
All devices
Supply to analog peripherals
DECOUPLE
All devices
Output of the internal Digital LDO & Digital logic power supply
IOVDD
All devices
GPIO supply voltage
USB_VREGI
All USB-enabled devices
Input to the internal 3.3 V LDO. Typically connected to the USB
5V supply.
USB_VREGO
All USB-enabled devices
Output of the internal 3.3 V LDO.
VREGVDD
EFM32 Series 2 and EFR32 Wireless Gecko only
Input to the DC-DC converter
VREGSW
EFM32 Series 2 and EFR32 Wireless Gecko only
DC-DC powertrain switching node
VREGVSS
EFM32 Series 2 and EFR32 Wireless Gecko only
DC-DC ground
DVDD
EFM32 Series 2 and EFR32 Wireless Gecko only
DC-DC feedback node and input to the internal Digital LDO
RFVDD
EZR32 and EFR32 Wireless Gecko
only
Supply to radio analog. Note, on EZR32, RFVDD also supplies
the radio power amplifier.
PAVDD
EFR32 Wireless Gecko only
Supply to radio power amplifier
1.4 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. Please see the
device data sheet for absolute maximum rating and additional details regarding relative system voltage constraints.
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AN0002: Hardware Design Considerations
Power Supply Overview
EFM32 Series 1 Gecko Power Supply Requirements
• VDD_DREG = AVDD = IOVDD
EFM32 Series 2 Gecko Power Supply Requirements
•
•
•
•
VREGVDD = AVDD (Must be the highest voltage in the system)
VREGVDD >= DVDD
VREGVDD >= IOVDD
DVDD >= DECOUPLE
EZR32 Power Supply Requirements
• VDD_DREG = AVDD = IOVDD = RFVDD
EFR32 Wireless Gecko Power Supply Requirements
•
•
•
•
•
•
VREGVDD = AVDD (Must be the highest voltage in the system)
VREGVDD >= DVDD
VREGVDD >= PAVDD
VREGVDD >= RFVDD
VREGVDD >= IOVDD
DVDD >= DECOUPLE
1.5 DECOUPLE
All EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Geckodevices include an internal linear regulator that powers the core
and digital logic. The DECOUPLE pin is the the output of the Digital LDO, and requires a 1 uF capacitor. The input to the Digital LDO
depends on the device family, as shown below.
1.5.1 DECOUPLE Pin — EFM32 Series 1 Gecko and EZR32
On EFM32 Series 1 Gecko and EZR32 devices, the Digital LDO is sourced by the VDD_DREG pin. DECOUPLE is the output of the
LDO.
VDD
VDD_DREG
CVDD
CVDD1
10 µF
0.1 µF
Digital
LDO
DECOUPLE
CDEC
1 µF
Digital
Logic
Figure 1.1. VDD_DREG and DECOUPLE on EFM32 Series 1 Gecko and EZR32 devices
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AN0002: Hardware Design Considerations
Power Supply Overview
1.5.2 DECOUPLE Pin — EFM32 Series 2 and EFR32 Wireless Gecko
On EFM32 Series 2 and EFR32 Wireless Gecko devices, the DVDD pin is the input supply to the Digital LDO, with the DECOUPLE pin
the output of the LDO.
VDD
Main
Supply
+
–
CDVDD1
DVDD
Digital
LDO
0.1 µF
CDEC
DECOUPLE
1 µF
Digital
Logic
Figure 1.2. DVDD and DECOUPLE on EFM32 Series 2 and EFR32 Wireless Gecko devices
1.6 IOVDD
The IOVDD pin(s) provide decoupling for all of the GPIO pins on the device. A 0.1 uF capacitor per IOVDD pin is recommend, along
with a 10 uF bulk capacitor. The bulk capacitor value may safely be reduced if there are other large bulk capacitors on the same supply
(e.g., if IOVDD=AVDD=VDD_VREG, and both VDD_VREG and AVDD both have a 10uF capacitor already).
VDD
+
–
CIOVDD_n
0.1 µF
...
Main
Supply
IOVDD_n
IOVDD_0
CIOVDD CIOVDD_0
10 µF 0.1 µF
Figure 1.3. IOVDD Decoupling
1.7 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.
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AN0002: Hardware Design Considerations
Power Supply Overview
1.7.1 AVDD Standard Decoupling
The figure below illustrates a standard approach for decoupling the AVDD pin(s). In general, the application should include one bulk
capacitor (CAVDD) of 10 µF, as well as one 10 nF capacitor per each AVDD pin (CAVDD_0 through CAVDD_n).
VDD
CAVDD_n
10 nF
+
–
CAVDD CAVDD_0
10 µF 10 nF
...
Main
Supply
AVDD_n
AVDD_0
Figure 1.4. AVDD Standard Decoupling
1.7.2 AVDD Improved Decoupling
The figure below illustrates an improved approach for decoupling and filtering the AVDD pin(s). In general, the application should include one bulk capacitor (CAVDD) of 10 µF, as well as one 10 nF capacitor per each AVDD pin (CAVDD_0 through CAVDD_n). In addition,
a ferrite bead and series 1 Ω resistor provide additional power supply filtering and isolation.
VDD FBVDD
+
–
1Ω
AVDD_n
CAVDD_n
10 nF
CAVDD CAVDD_0
10 µF 10 nF
...
Main
Supply
RAVDD
AVDD_0
Figure 1.5. AVDD Improved Decoupling
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AN0002: Hardware Design Considerations
Power Supply Overview
The table below lists some recommended ferrite bead part numbers suitable for AVDD filtering.
Table 1.2. Recommended Ferrite Beads
Manufacturer
Part Number
Impedance
IMAX (mA)
DCR (Ω)
Operating Temperature (°C)
Package
Würth Electronics
74279266
1 kΩ @ 100 MHz
200
0.600
-55 to +125
0603/1608
Murata
BLM21BD102SN1D
1 kΩ @ 100 MHz
200
0.400
-55 to +125
0805/2012
1.8 USB (USB_VREGI & USB_VREGO)
Some Gecko devices integrate a USB controller and a 3.3V LDO. The figure below illustrates a standard approach for connecting and
decoupling the USB_VREGI, and USB_VREGO pins. In addition, the USB5V sense line (USB_VBUS) is shown connected directly to
VUSB.
To avoid violating the USB specification, the total capacitance on VUSB should not exceed 10 µF. Consult AN0046: USB Hardware Design Guide for detailed hardware guidance for USB applications.
USB_VBUS
VUSB
USB
5V
+
–
USB_VREGI
CUSB_VREGI
4.7 µF
VREGO
3.3V
LDO
CUSB_VREGO USB_VREGO
1 µF
Figure 1.6. USB_VREGI and USB_VREGO Decoupling
1.9 DC-DC— EFM32 Series 2 and EFR32 Wireless Gecko
EFM32 Series 2 and EFR32 Wireless Gecko devices may take advantage of an onboard DC-DC converter for improved power efficiency. However, due to additional switching noise present on the DC-DC converter output (VDCDC), some additional filtering components
may be required.
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AN0002: Hardware Design Considerations
Power Supply Overview
1.9.1 DC-DC — Unused
When the DC-DC converter isn't used, the DVDD pin should be shorted to the VREGVDD pin. VREGSW must be left floating, and
VREGVSS should be grounded.
VDD
Main
Supply
Bypass
Switch
VREGVDD
CVDD CVDD1
10 µF 0.1 µF
+
–
VREGSW
VREGVSS
CDVDD
0.1 µF
DC-DC
Driver
OFF
DC-DC
DVDD
Figure 1.7. Configuration when the DC-DC converter is unused
1.9.2 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) as shown in the figure below. In this configuration, the DC-DC Output (VDCDC) is connected to DVDD. 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.
VDD
Main
Supply
CVDD CVDD1
10 µF 0.1 µF
+
–
VDCDC
LDCDC
4.7 µH
CDCDC
1 µF
Bypass
Switch
VREGVDD
VREGSW
VREGVSS
DC-DC
Driver
OFF
DC-DC
DVDD
CDVDD
0.1 µF
Figure 1.8. DC-DC Converter Powering DVDD
1.10 Radio (RFVDD & PAVDD) — EFR32 Wireless Gecko
On EFR32 Wireless Gecko devices, the radio power supplies (PAVDD and RFVDD) will typically be powered from one of two sources:
1. The integrated DC-DC converter. This option provides improved power efficiency, although it only supports up to 13 dBm transmit
power. And due to additional switching noise present on the DC-DC converter output (VDCDC), some additional filtering components may be required.
2. The main supply. This option is less efficient, but requires less filtering components and supports > 13 dBm transmit power.
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AN0002: Hardware Design Considerations
Power Supply Overview
1.10.1 RFVDD and PAVDD — Powered from DC-DC
Both RFVDD and PAVDD may be powered from the DC-DC converter output (VDCDC) for lowest power operation. Note, however, that
the maximum transmit power is limited to 13 dBm when PAVDD is powered from VDCDC. If higher power is required, PAVDD should be
powered from the main supply instead of the DC-DC output.
VDCDC
CRFVDD
220 nF
CPAVDD
220 nF
RF
Analog
PAVDD
RF
Power
Amplifier
CRFVDD1
10 pF
LPAVDD
22 nH
RFVDD
CPAVDD1
10 pF
Figure 1.9. RFVDD and PAVDD Decoupling (2.4 GHz Application, both supplies powered from DC-DC output)
The minimal BOM option eliminates CRFVDD1 and CPAVDD1, which may allow acceptable RF performance at lower power levels. For
more complete details on the minimal BOM option, along with performance comparisons, refer to AN933: EFR32 2.4 GHz Minimal
BOM.
Table 1.3. RFVDD & PAVDD Decoupling Values, Powered from DC-DC Converter
Application
CRFVDD
CRFVDD1
LPAVDD
CPAVDD
CPAVDD1
2.4 GHz
220 nF
10 pF
22 nH
220 nF
10 pF
2.4 GHz (minimal
BOM)
220 nF
-
22 nH
220 nF
-
sub-GHz
220 nF
56-270 pF
100-270 nH
220 nF
56 - 270 pF
sub-GHz (minimal
BOM)
220 nF
-
100-270 nH
220 nF
-
Table 1.4. Recommended LPAVDD 22 nH Inductor
Manufacturer
Part Number
Inductance (nH)
IMAX (mA)
DCR (Ω)
Operating Temperature (°C)
Package
Murata
LQG15HS22NJ02D
22±5%
300
0.420
-55 to +125
0402/1005
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AN0002: Hardware Design Considerations
Power Supply Overview
1.10.2 RFVDD and PAVDD — Powered from Main Supply
When greater than 13 dBm transmit power is required, PAVDD should be powered directly from the main supply, and RFVDD may be
powered from either the main supply or the DC-DC output (VDCDC). Note that in this configuration, the LPAVDD filter inductor is not
shown on the PAVDD input, because the main supply is presumed to be less noisy than VDCDC.
VDD
Main
Supply
+
–
CRFVDD
220 nF
CPAVDD
220 nF
RFVDD
RF
Analog
PAVDD
RF
Power
Amplifier
CRFVDD1
10 pF
CPAVDD1
10 pF
Figure 1.10. RFVDD and PAVDD Decoupling (2.4 GHz Application, both supplies powered from Main Supply)
The minimal BOM option eliminates CRFVDD1 and CPAVDD1, which may allow acceptable RF performance at lower power levels. For
more complete details on the minimal BOM option, along with performance comparisons, refer to AN933: EFR32 2.4 GHz Minimal
BOM.
Table 1.5. RFVDD & PAVDD Decoupling Values, Powered from Main Supply
Application
CRFVDD
CRFVDD1
LPAVDD
CPAVDD
CPAVDD1
2.4 GHz
220 nF
10 pF
-
220 nF
10 pF
2.4 GHz (minimal
BOM)
220 nF
-
-
220 nF
-
sub-GHz
220 nF
56-270 pF
-
220 nF
56 - 270 pF
sub-GHz (minimal
BOM)
220 nF
-
-
220 nF
-
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2. Example Power Supply Configurations
2.1 EFM32 Series 1 Gecko and EZR32 Example Power Supply Configurations
Several EFM32 Series 1 Gecko and EZR32 example power supply configurations are shown below.
2.1.1 EFM32 Series 1 and 2 Gecko — Standard Decoupling Example
The figure below illustrates a standard approach for decoupling. This configuration is simple and uses minimal components, while providing sufficient noise suppression for many typical applications.
VDD
Main
Supply
CVDD CVDD1
10 µF 0.1 µF
+
–
AVDD_n
...
CAVDD CAVDD_0
10 µF 10 nF
Digital
LDO
...
CAVDD_n
10 nF
VDD_DREG
IOVDD_n
IOVDD_0
AVDD_0
Digital
Logic
VSS
CIOVDD_n
0.1 µF
DECOUPLE
CDEC
CIOVDD_0
0.1 µF
1
ANASW
CIOVDD
10 µF
IOVDD
1 µF
Figure 2.1. EFM32 Series 1 and 2 Gecko Standard Decoupling Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.1.2 EFM32 Series 1 and 2 Gecko — 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 1.2 Recommended Ferrite Beads on page 5 for recommended ferrite bead part numbers.
VDD
Main
Supply
+
–
FBAVDD
RAVDD
1Ω
CVDD CVDD1
10 µF 0.1 µF
AVDD_n
...
CAVDD CAVDD_0
10 µF 10 nF
Digital
LDO
...
CAVDD_n
10 nF
VDD_DREG
IOVDD_n
IOVDD_0
AVDD_0
Digital
Logic
VSS
CIOVDD_n
0.1 µF
DECOUPLE
CDEC
CIOVDD_0
0.1 µF
1
ANASW
CIOVDD
10 µF
IOVDD
1 µF
Figure 2.2. EFM32 Series 1 and 2 Gecko Improved AVDD Filtering Example
Note: Note that during power-on for EFM32GG and EFM32G Gecko devices, the AVDD_x pins must not be powered up after the
IOVDD_x and VDD_DREG pins. If the rise time of the power supply is short, the filter in Figure 2.2 EFM32 Series 1 and 2 Gecko
Improved AVDD Filtering Example on page 10 can cause a significant delay on the AVDD_x pins. For improved AVDD filtering for
EFM32GG and EFM32G Gecko devices, refer to section 2.1.3 EFM32GG and EFM32G Gecko Only — Improved AVDD Filtering Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.1.3 EFM32GG and EFM32G Gecko Only — Improved AVDD Filtering Example
Similar to section 2.1.2 EFM32 Series 1 and 2 Gecko — Improved AVDD Filtering Example, the figure below shows improved noise
suppression and isolation between the digital and analog power pins for high ADC accuracy. Refer to Table 1.2 Recommended Ferrite
Beads on page 5 for recommended ferrite bead part numbers.
There is a unique restriction on EFM32GG and EFM32G Gecko devices that at power on, the AVDD_x pins must not be powered up
after the IOVDD_x and VDD_DREG pins. If the rise time of the power supply is short, the AVDD filter can cause a significant delay on
the AVDD_x pins. Therefore, for EFM32GG and EFM32G Gecko devices, an additional 1 Ω resistor should also be added to the
VDD_DREG supply path, as shown in the figure below.
VDD FBVDD
Main
Supply
+
–
RDVDD
1Ω
RAVDD
1Ω
CVDD CVDD1
10 µF 0.1 µF
AVDD_n
...
CAVDD CAVDD_0
10 µF 10 nF
Digital
LDO
...
CAVDD_n
10 nF
VDD_DREG
IOVDD_n
IOVDD_0
AVDD_0
Digital
Logic
VSS
CIOVDD_n
0.1 µF
DECOUPLE
CIOVDD_0
0.1 µF
1
ANASW
CDEC
CIOVDD
10 µF
IOVDD
1 µF
Figure 2.3. EFM32 Series 1 and 2 Gecko Improved AVDD Filtering Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.1.4 EZR32 — Standard Decoupling Example
The figure below illustrates a standard approach for decoupling a EZR32 device.
VDD
Main
Supply
CVDD CVDD1
10 µF 0.1 µF
+
–
VDD_DREG
IOVDD_n
AVDD_n
AVDD_0
RFVDD_1
1
CRFVDD1 CRFVDD2
0.1 µF 470 pF
1
CIOVDD_n
0.1 µF
IOVDD_0
Radio
CRFVDD
2.2 µF
...
CAVDD CAVDD_0
10 µF 10 nF
Digital
LDO
...
CAVDD_n
10 nF
RFVDD_2
CRFVDD2
100 pF
Digital
Logic
DECOUPLE
CIOVDD_0
0.1 µF
1
ANASW
CIOVDD
10 µF
IOVDD
CDEC
1 µF
Figure 2.4. EZR32 Standard Decoupling Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.2 EFM32 Series 2 and EFR32 Wireless Gecko Example Power Supply Configurations
EFM32 Series 2 and EFR32 Wireless Gecko applications can enable the DC-DC converter to maximize power savings in embedded
applications. 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 Configurations and DC-DC.
At power on, the EFM32 Series 2 and EFR32 Wireless Gecko devices boot into an initial power configuration with the DC-DC module
bypassed internally (i.e, the VREGVDD pin is shorted internally to the DVDD pin). After startup, software must change the power configuration settings to configure the DC-DC and any associated external components as described in the following subsections.
Note: Figure 2.5 EFM32 Series 2 and EFR32 Wireless Gecko Startup Configuration on page 13 is only provided to show the device
startup default supply configuration, and is not a usable application configuration.
VDD
Main
Supply
+
–
VREGVDD
IOVDD
AVDD
Bypass
Switch
VREGSW
DC-DC
Driver
FLASH
ON
0
DC-DC
VREGVSS
1
ANASW
Analog
Blocks
DVDD
Digital
LDO
Digital
Logic
DECOUPLE
Figure 2.5. EFM32 Series 2 and EFR32 Wireless Gecko Startup Configuration
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.2.1 EFR32 Wireless Gecko — No DC-DC, 2.4 GHz, <= 13 dBm Example
For space-sensitive or cost-sensitive applications, or when power efficiency isn't important, the DC-DC converter may be unused. In this
configuration:
• The DC-DC converter is programmed in Off mode, and the Bypass switch is Off.
• The DVDD pin must be powered externally - typically, it is shorted to the main supply.
• In addition, RFVDD, PAVDD, IOVDD, and AVDD are all connected to the main supply.
• VREGSW should be left disconnected.
VDD
Main
Supply
CVDD CVDD1
10 µF 0.1 µF
+
–
CIOVDD CIOVDD1
1 µF 0.1 µF
CAVDD CAVDD1
10 µF 10 nF
VREGVDD
IOVDD
AVDD
Bypass
Switch
VREGSW
DC-DC
Driver
CDEC
1 µF
OFF
0
DC-DC
VREGVSS
CDVDD
0.1 µF
FLASH
1
ANASW
Analog
Blocks
DVDD
Digital
LDO
Digital
Logic
RF
Power
Amplifier
RF
Analog
DECOUPLE
RFVDD
CRFVDD
220 nF
LPAVDD
22 nH
PAVDD
CRFVDD1
10 pF
CPAVDD1
10 pF
CPAVDD
220 nF
Figure 2.6. EFR32 Wireless Gecko No DC-DC, 2.4 GHz, <= 13 dBm Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.2.2 EFR32 Wireless Gecko — DC-DC, 2.4 GHz, <= 13 dBm Example
For the lowest power radio applications, the DC-DC converter can be used to power the DVDD supply, as well as RFVDD and PAVDD.
In this configuration:
• The DC-DC Output (VDCDC) is connected to DVDD. DVDD powers the internal Digital LDO which powers the digital circuits.
• Both radio power supplies (RFVDD and PAVDD) are also powered from the DC-DC Output.
• AVDD is connected to the main supply voltage. The internal analog blocks may be powered from AVDD or DVDD, depending on the
ANASW configuration. Flash is always powered from the AVDD pin.
• IOVDD could be connected to either the main supply (as shown below) or to VDCDC, depending on the system IO requirements.
VDD
Main
Supply
+
–
VREGVDD
VDCDC
CDVDD
0.1 µF
CDEC
1 µF
IOVDD
AVDD
Bypass
Switch
LDCDC
4.7 µH
CDCDC
1 µF
CIOVDD CIOVDD1
1 µF 0.1 µF
CAVDD CAVDD1
10 µF 10 nF
CVDD CVDD1
10 µF 0.1 µF
VREGSW
DC-DC
Driver
FLASH
OFF
0
DC-DC
VREGVSS
1
ANASW
Analog
Blocks
DVDD
Digital
LDO
Digital
Logic
RF
Power
Amplifier
RF
Analog
DECOUPLE
RFVDD
CRFVDD
220 nF
LPAVDD
22 nH
PAVDD
CRFVDD1
10 pF
CPAVDD
220 nF
CPAVDD1
10 pF
Figure 2.7. EFR32 Wireless Gecko DC-DC, 2.4 GHz, <= 13 dBm Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.2.3 EFR32 Wireless Gecko — DC-DC, 2.4 GHz, > 13 dBm Example
When high power (>13 dBm) radio output power is required, PAVDD should be connected to the main supply. The DC-DC converter
can continue to power DVDD, IOVDD, and RFVDD. This power configuration is illustrated below.
VDD
Main
Supply
+
–
CVDD CVDD1
10 µF 0.1 µF
VREGVDD
VDCDC
CDVDD
0.1 µF
CDEC
1 µF
IOVDD
AVDD
Bypass
Switch
LDCDC
4.7 µH
CDCDC
1 µF
CIOVDD CIOVDD1
1 µF 0.1 µF
CAVDD CAVDD1
10 µF 10 nF
VREGSW
DC-DC
Driver
FLASH
OFF
0
DC-DC
VREGVSS
1
ANASW
Analog
Blocks
DVDD
Digital
LDO
Digital
Logic
RF
Power
Amplifier
RF
Analog
DECOUPLE
RFVDD
CRFVDD
220 nF
LPAVDD
22 nH
PAVDD
CRFVDD1
10 pF
CPAVDD1
10 pF
CPAVDD
220 nF
Figure 2.8. EFR32 Wireless Gecko DC-DC, 2.4 GHz, > 13 dBm Example
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AN0002: Hardware Design Considerations
Example Power Supply Configurations
2.2.4 EFM32 Series 2 Gecko — DC-DC Example
The diagram below illustrates a typical connection configuration for a EFM32 Series 2 Gecko device using the DC-DC converter.
VDD
Main
Supply
VREGVDD
VDCDC
CIOVDD CIOVDD1
1 µF 0.1 µF
CAVDD CAVDD1
10 µF 10 nF
CVDD CVDD1
10 µF 0.1 µF
+
–
IOVDD
AVDD
Bypass
Switch
LDCDC
4.7 µH
CDCDC
1 µF
VREGSW
DC-DC
Driver
OFF
0
DC-DC
VREGVSS
CDVDD
0.1 µF
FLASH
1
ANASW
Analog
Blocks
DVDD
Digital
LDO
CDEC
1 µF
Digital
Logic
DECOUPLE
Figure 2.9. EFM32 Series 2 Gecko DC-DC Example
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AN0002: Hardware Design Considerations
Debug Interface and External Reset Pin
3. Debug Interface and External Reset Pin
3.1 Serial Wire Debug
The Serial Wire (SWD) interface is supported by all EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko devices. The
SWD debug interface consists of the SWCLK (clock input) and SWDIO (data in/out) lines, in addition to the optional SWO (serial wire
output). The SWO line is used for instrumentation trace and program counter sampling, and is not needed for programming and normal
debugging. However, it can be valuable in advanced debugging scenarios, and it is therefore recommended to include this line in a
design.
The connection to an ARM 20-pin debug connector is shown in the following figure. Pins with no connection should be left unconnected.
VMCU
VMCU
VDD
PF1
PF0
SWDIO
SWCLK
PF2 or PC15
SWO
RESETn
Reset
Vtarget
1
2
3
4
5
6
7
8
9 10
VSS
11 12
13 14
15 16
17 18
Gecko Device
19 20
ARM 20 Pin Header
Figure 3.1. Connecting the Gecko Device to an ARM 20-pin Debug Header
Note: The Vtarget connection is not for supplying power. The debugger uses Vtarget as a reference voltage for the debugger's level
translators.
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AN0002: Hardware Design Considerations
Debug Interface and External Reset Pin
3.2 JTAG Debug — EFM32 Series 2 and EFR32 Wireless Gecko
The JTAG debug interface is supported by the EFM32 Series 2 and EFR32 Wireless Gecko devices and consists of the TDI (data input), TDO (data output), TCLK (clock), and TMS (input mode select) lines. TDI carries input data, and is sampled on the rising edge of
TCLK. TDO carries output data and is shifted out on the falling edge of TCLK. TCLK is the debug clock line. Finally, TMS is the input
mode select signal, and is used to navigate through the Test Access Port state machine.
The connection to an ARM 20-pin debug connector is shown in the following figure. Pins with no connection should be left unconnected.
VMCU
VMCU
Vtarget
IOVDD
PF3
PF1
PF0
PF2
RESETn
TDI
TMS
TCLK
TDO
1
2
3
4
5
6
7
8
9 10
Reset
11 12
13 14
VSS
15 16
17 18
19 20
Gecko Device
ARM 20 Pin Header
Figure 3.2. Connecting the EFM32 Series 2 and EFR32 Wireless Gecko Device to an ARM 20-pin Debug Header
Note: The Vtarget connection is not for supplying power, only sensing the target voltage.
3.3 External Reset Pin (RESETn)
Forcing the RESETn pin low generates a reset of the EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko device. The
RESETn pin includes an internal pull-up resistor and can therefore be left unconnected if no external reset source is required. Also
connected to the RESETn line is a low-pass filter which prevents noise glitches from causing unintended resets. The characteristics of
the pullup and input filter is identical to the corresponding characteristic of a GPIO pin, which is found in the device data sheet.
Note: To apply an external reset source to this pin, drive this pin low during reset. The internal pull-up ensures that the reset is released. This pin should not be connected to an external pull-up or driven high while the device is unpowered, as this could damage the
device. This is also important when using back-up power mode, as the internal pull-up automatically switches to the back-up power rail,
which could end up back-powering the entire system through the external pull up.
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AN0002: Hardware Design Considerations
External Clock Sources
4. External Clock Sources
4.1 Introduction
The EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko devices support different external clock sources to generate
the low and high frequency clocks in addition to the internal LF and HF RC oscillators. The possible external clock sources for both the
LF and HF domains are external oscillators (square or sine wave) or crystals/ceramic resonators. This section describes how the external clock sources should be connected.
For additional information on the external oscillators, refer to the application note AN0016: Oscillator Design Considerations. Application
notes can be found on the Silicon Labs website (www.silabs.com/32bit-appnotes) or in Simplicity Studio using the [Application Notes]
tile.
4.2 Low Frequency Clock Sources
The external low frequency clock can be generated from a crystal/ceramic resonator or from an external clock source.
4.2.1 Low Frequency Crystals and Ceramic Resonators — EFM32 Series 1 Gecko and EZR32
The hardware configuration of the crystal and ceramic resonator is indicated in Figure 4.1 Low Frequency Crystal on page 20. The
crystal is to be connected across the LFXTAL_N and LFXTAL_P pins of the EFM32 Series 1 Gecko and EZR32.
LFXTAL_N
LFXTAL_P
32 kHz
CL1
CL2 Gecko Device
Figure 4.1. Low Frequency Crystal
The crystals/ceramic resonators oscillate mechanically and have an electrical equivalent circuit as shown in Figure 4.2 Equivalent Circuit of a Crystal/Ceramic Resonator on page 20. In the electrical circuit, CS represents the motional capacitance, LS the motional inductance, RS the mechanical losses during oscillation, and C0 the parasitic capacitance of the package and pins. CL1 and CL2 represent the load capacitance. This circuit is valid for both crystals and ceramic resonators.
CS
RS
C0
CL1
LS
CL2
Figure 4.2. Equivalent Circuit of a Crystal/Ceramic Resonator
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AN0002: Hardware Design Considerations
External Clock Sources
4.2.2 Low Frequency Crystals and Ceramic Resonators — EFM32 Series 2 and EFR32 Wireless Gecko
The hardware configuration of the crystal and ceramic resonator is indicated in Figure 4.3 Low Frequency Crystal - EFM32 Series 2 and
EFR32 Wireless Gecko on page 21. The crystal is to be connected across the LFXTAL_N and LFXTAL_P pins of the EFM32 Series 2
and EFR32 Wireless Gecko. This circuit is valid for both crystals and ceramic resonators.
LFXTAL_N
32.768 kHz
CTUNING
LFXTAL_P
CTUNING
Gecko Device
Figure 4.3. Low Frequency Crystal - EFM32 Series 2 and EFR32 Wireless Gecko
The difference between this crystal configuration and that of the EFM32 Series 1 Gecko and EZR32 is that the need for external load
capacitors CL1 and CL2 have been eliminated. These load capacitors are now on-chip and can be tuned by software. The EFM32 Series 2 and EFR32 Wireless Gecko devices support low frequency crystals with load capacitance in the range of 6 pF to 18 pF. Check
device specific data sheets and reference manuals for load capacitance values and instructions for tuning the internal load capacitances.
4.2.3 Low Frequency External Clocks
The EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko devices can also be clocked by an LF external clock source. To
select a proper external oscillator, consider the specifications such as frequency, aging, stability, voltage sensitivity, rise and fall time,
duty cycle, and signal levels. The external clock signal can either be a square wave or sine signal with a frequency of 32.768 kHz. The
external clock source must be connected as indicated in Figure 4.4 Low Frequency External Clock on page 21.
When a square wave source is used, the LFXO buffer must be in bypass mode. The clock signal must toggle between 0 and VDD and
the duty cycle must be close to 50%, as specified in the device data sheet. When a sine source is used, the amplitude must be in
accordance with the device data sheet. The sine signal is buffered through the LFXO buffer, whose input is ac-coupled.
External
source
LFXTAL_N
LFXTAL_P
(High Z)
Gecko Device
Figure 4.4. Low Frequency External Clock
4.3 High Frequency Clock Sources
The external high frequency clock can be generated from a crystal/ceramic resonator or from an external square or sine wave source.
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AN0002: Hardware Design Considerations
External Clock Sources
4.3.1 High Frequency Crystals and Ceramic Resonators — EFM32 Series 1 Gecko and EZR32
The hardware configuration of the crystal and ceramic resonator is indicated in Figure 4.5 High Frequency Crystal Oscillator on page
22. The crystal should be connected across the HFXTAL_N and HFXTAL_P pins.
The electrical equivalent circuit of the HF crystal/ceramic resonators is equal to the one for LF crystals/ceramic resonators in the figure
below.
Placement of CL is important for proper operating frequency.
HFXTAL_N
HFXTAL_P
4-32 MHz
CL1
CL2
Gecko Device
Figure 4.5. High Frequency Crystal Oscillator
4.3.2 High Frequency Crystals and Ceramic Resonators ─ EFM32 Series 2 and EFR32 Wireless Gecko
The hardware configuration of the crystal and ceramic resonator is indicated in Figure 4.6 High Frequency Crystal Oscillator - EFM32
Series 2 and EFR32 Wireless Gecko on page 22. The crystal should be connected across the HFXTAL_N and HFXTAL_P pins.
The difference between this crystal configuration and that of the EFM32 Series 1 Gecko and EZR32 is that the need for external load
capacitors CL1 and CL2 have been eliminated. These load capacitors are now on-chip and can be tuned by software. The EFM32 Series 2 and EFR32 Wireless Gecko devices support high frequency crystals with load capacitance in the range of 6 pF to 12 pF. Check
device specific data sheets and reference manuals for load capacitance values and instructions for tuning the internal load capacitances.
HFXTAL_N
38 – 40 MHz
CTUNING
HFXTAL_P
CTUNING
Gecko Device
Figure 4.6. High Frequency Crystal Oscillator - EFM32 Series 2 and EFR32 Wireless Gecko
Note: Some devices are subject to the 38 - 40 MHz frequency limit for the high frequency crystal oscillator, whereas other devices will
have a wider frequency range. Please consult the device-specific data sheet for more information.
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AN0002: Hardware Design Considerations
External Clock Sources
4.3.3 High Frequency External Clocks
The EFM32 Series 1 and 2 Gecko, EZR32, and EFR32 Wireless Gecko devices can also be clocked by an external HF clock source.
To select a proper external oscillator, consider the specifications such as frequency, aging, stability, voltage sensitivity, rise and fall
time, duty cycle and signal levels. The external clock signal can either be square wave or a sine signal with a frequency in accordance
with the device data sheet. The external clock source must be connected as indicated in Figure 4.7 External High Frequency Clock on
page 23.
When a square wave source is used, the HFXO buffer must be in bypass mode. The clock signal must toggle between 0 and VDD and
the duty cycle must be close to 50%. Refer to the device data sheet for further details. When a sine source is used, the sine amplitude
must be in accordance with what is specified in the device data sheet. The sine signal is buffered through the HFXO buffer, whose input
is ac-coupled.
External
source
HFXTAL_N
HFXTAL_P
(High Z)
Gecko Device
Figure 4.7. External High Frequency Clock
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AN0002: Hardware Design Considerations
Reference Design
5. Reference Design
When starting a new EFM32 Series 1 Gecko and EZR32 design, some parts of the layout are almost always required regardless of the
application. Attached to this application note are example schematics for power decoupling, reset, external clocks, and debug interface.
Using this reference design as a template can improve development speed in the early stages of a new design. The reference design
and included symbols are compatible with Cadence OrCAD 9.0 and later versions.
This application note does not include footprints for the devices, but these can be found in *.bxl format on http://www.silabs.com.
5.1 Contents
The application note folder includes several zip files with the following contents:
•
•
•
•
•
CSV pin list files
Edif symbols
OrCAD OLB symbols
OrCAD DSN example schematics
PDF example schematics
The schematics and symbols are included for the following device families:
•
•
•
•
•
•
•
EFM32ZG
EFM32HG
EFM32TG
EFM32G
EFM32LG
EFM32WG
EFM32GG
A generic symbol is included for the EZR32 family.
5.2 Comments on the Schematics
5.2.1 Power Supply Decoupling
The decouple pin uses a 1 µF capacitor to filter transients in the power domain for the internal voltage regulator.
Each power pin has a 100 nF decoupling capacitor in addition to the common 10 µF decoupling capacitor, as described in 2.1 EFM32
Series 1 Gecko and EZR32 Example Power Supply Configurations. The digital power supply is separated from the analog power supply
to reduce EMI. To further improve the switching noise of the analog power, an EMI suppressor is put in series between VMCU and the
analog power pins.
The active low reset pin is connected to ground through a normally open switch, as well as to the debug interface connector.
5.2.2 Debug Interface
A standard ARM 20-pin debug connector is connected to the EFM32 Series 1 Gecko and EZR32 device debug pins.
5.2.3 High/Low Frequency Clock
Both the high and low frequency clock pins are connected to crystal oscillators using two of the recommended crystals from the
AN0016: Oscillator Design Considerations application note.
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AN0002: Hardware Design Considerations
Revision History
6. Revision History
6.1 Revision 1.45
2016-6-15
Added note about ceramic capacitor selection for extended temperature range devices (i.e., -55 °C – +125°C)
Added power supply pin overview
Added section on USB power pins
Updated all the power supply connection diagrams
Added EZR32 power supply diagram
6.2 Revision 1.44
2015-11-13
Added power configuration and crystal resonator info for EFR32 Wireless Gecko portfolio devices.
6.3 Revision 1.43
2015-10-21
Added power configuration and crystal resonator info for EFM32 Series 2 Gecko devices.
Added symbols and schematics for EFM32JG and EZR32PG devices.
6.4 Revision 1.42
2015-03-04
Added symbols and schematics for EFM32HG and EZR32LG devices.
6.5 Revision 1.41
2015-02-13
Added EZR32 devices.
Updated format.
6.6 Revision 1.40
2014-05-07
Added symbols and schematics for EFM32WG and EFM32ZG devices.
Corrected numbering for EM4WU pins for EFM32TG devices in symbols and schematics.
6.7 Revision 1.36
2013-10-14
New cover layout
6.8 Revision 1.35
2013-08-14
Updated section on power supply decoupling
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AN0002: Hardware Design Considerations
Revision History
6.9 Revision 1.34
2013-05-08
Added note about decoupling capacitor purpose.
Added new design files for new packages and devices.
6.10 Revision 1.33
2012-03-21
Added CSV and Edif formats for schematic symbols.
6.11 Revision 1.32
2012-03-16
Added OrCAD reference designs and OrCAD symbols for more parts.
6.12 Revision 1.31
November 23th, 2010.
Corrected schematic values.
Added information on power sequencing considerations.
6.13 Revision 1.30
November 17th, 2010.
Added information on alternate schematic recommendations.
6.14 Revision 1.20
September 13th, 2010.
Merged sections on PCB design considerations and external clock sources.
Modified chapter on external clock sources to correspond with AN0016: EFM32 Oscillator Design Considerations.
Added OrCAD and PDF reference designs.
6.15 Revision 1.10
May 6th, 2010.
Added debug interface section.
6.16 Revision 1.00
October 21th, 2009.
Initial revision.
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