4. Power Supply and Reset
4.1 Radio Board Power Selection
The EFR32 on a Wireless Starter 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. The figure
below shows how the different power sources can be selected with the slide switch.
VMCU
AEM
USB
BAT
USB Mini-B
Connector
Advanced
Energy
Monitor
3 V Lithium Battery
(CR2032)
BA
T
US
B
AE
M
LDO
EFR32
5 V
3.3 V
Figure 4.1. Power Switch
With the switch in the
AEM
position, a low noise 3.3 V 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 measurements
and energy debugging/profiling.
With the switch in the
USB
position, radio boards with USB-support can be powered by a regulator on the radio board itself. BRD4183A
does not contain a USB regulator, and setting the switch in the
USB
position will cause the EFR32 to be unpowered.
Finally, 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 recommended switch position when powering the radio board
with an external power source.
Note:
The current sourcing capabilities of a coin cell battery might be too low to supply certain wireless applications.
Note:
The AEM can only measure the current consumption of the EFR32 when the power selection switch is in the
AEM
position.
UG431: EFR32xG22 2.4 GHz 6 dBm QFN32 Wireless Starter Kit User's Guide
Power Supply and Reset
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