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; or
• 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.
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 WSTK Mainboard is used to power the Radio Board. This LDO is
again powered from the debug USB cable. The Advanced Energy Monitor 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. BRD4259A
does not contain an USB regulator, and setting the switch in the
USB
postition 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 Advanced Energy Monitor can only measure the current consumption of the EFR32 when the power selection switch is in
the
AEM
position.
UG321: EFR32FG14 2400/434 MHz 10 dBm Dual Band Radio Board and Wireless Starter Kit User's Guide
Power Supply and Reset
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