4. Power Supply and Reset
4.1 Radio Board Power Selection
The EFR32 on a Wireless Pro Kit can be powered by one of these sources:
• The debug USB cable
• A 3 V coin cell battery
• A USB regulator on the radio board (for devices with USB support only)
The power source for the radio board is selected with the slide switch in the lower left corner of the Wireless STK Mainboard or the
Wireless Pro Kit Mainboard. The figure below shows how the different power sources can be selected with the slide switch.
VMCU
AEM
SELF (USB)
BAT
USB
Connector
Advanced
Energy
Monitor
LDO
EFR32
5 V
VOUT
BA
T
SELF
(USB)
AEM
3 V Lithium Battery
(CR2032)
Figure 4.1. Power Switch
Note:
The middle position is denoted by "USB" on the Wireless STK Mainboard, while it is denoted by "SELF" on the Wireless Pro Kit
Mainboard. The slide switch functions the same on both mainboards.
Note:
The AEM can only measure the current consumption of the EFR32 when the power selection switch is in the
AEM
position.
AEM position:
With the switch in the AEM position, a low noise LDO on the mainboard is used to power the radio board. This LDO is
again powered from the debug USB cable. The AEM is now also connected in series, allowing accurate high speed current measure-
ments and energy debugging/profiling.
USB position:
With the switch in the USB position, radio boards with USB-support can be powered by a regulator on the radio board
itself. BRD4186C does not contain a USB regulator, and setting the switch in the
USB
position will cause the EFR32 to be unpowered.
BAT position:
With the switch in the BAT position, a 20 mm coin cell battery in the CR2032 socket can be used to power the device.
With the switch in this position, no current measurements are active. This is the switch position that should be used when the radio
board is powered with an external power source. The Wireless Pro Kit Mainboard (BRD4002A) features an additional 2-pin JST con-
nector connected in paralell to the CR2032 socket that can be used with an external power source between 1.8 V and 3.6 V instead of
a coin cell. The coin cell battery is not protected from reverse current, and it is therefore important to remove the coin cell battery from
the CR2032 socket if applying external power.
Note:
The current sourcing capabilities of a coin cell battery might be too low to supply certain wireless applications.
UG525: EFR32xG24 2.4 GHz 10 dBm Wireless Pro Kit User's Guide
Power Supply and Reset
silabs.com
| Building a more connected world.
Rev. 1.0 | 17
