Power Supply And Reset; Radio Board Power Selection - Silicon Laboratories EFR32xG21B User Manual

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.
5 V
USB Mini-B
Connector
3 V Lithium Battery
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. BRD4181C
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.
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Advanced
3.3 V
LDO Energy
Monitor
(CR2032)
Figure 4.1. Power Switch
UG428: EFR32xG21B 2.4 GHz 10 dBm Wireless Starter Kit User's Guide
AEM
VMCU
USB
BAT
Power Supply and Reset
EFR32
Rev. 1.0 | 14