EZR32WG-434MHZ Datasheet, PDF (7/29 Pages) Silicon Laboratories – Ethernet and USB connectivity

4. Power Supply and Reset
EZR32WG 434MHz Wireless Starter Kit
Power Supply and Reset
4.1 MCU Power Selection
The EZR32 Wonder Gecko MCU on the WSTK6221 is designed to be powered by three different sources:
• Through the on-board debugger.
• Through the EZR32's own USB regulator.
• By a 3V Battery.
Selecting the power source is done with the slide switch in the lower left corner of the board. Figure Figure 4.1 WSTK6221 Power
Switch on page 4 shows how the different power sources can be selected with the slide switch.
BAT USB AEM
5V
USB Mini-B
Connector
LDO
3.3V ^Advanced
Energy
Monitor
AEM
USB
BAT
VMCU
3V Lithium Battery
( CR2032 )
USB_VREGO
(3..3V)
Wireless
MCU
USB_VREGI
(5V)
USB Micro-B
Connector
Figure 4.1. WSTK6221 Power Switch
With the switch in the DBG position, an on-board low noise LDO with a fixed output voltage of 3.3V is used to power the MCU. This
LDO is again powered from the "J-Link" 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, the integrated linear regulator in the EZR32 Wonder Gecko MCU is used to power the rest of the
chip as well as the USB PHY. This allows a USB device application where the MCU acts as a bus powered device.
Finally, with the switch in the BAT position, a 20mm coin cell battery in the CR2032 socket can be used to power the device.
Note:
The Advanced Energy Monitor can only measure the current consumption of the EZR32 when the power selection switch is in the DBG
position.
4.2 Board Controller Power
The Board Controller is responsible for important features such as the debugger and the Advanced Energy Monitor, and is powered
exclusively through the USB port in the top left corner of the board. This part of the kit resides on a separate power domain, so a differ-
ent power source can be selected for the MCU while retaining debugging functionality. This power domain is also isolated to prevent
current leakage from the MCU power domain when power to the Board Controller is removed.
4.3 Backup Power Domain
The kit contains a backup capacitor that can be used together with the EZR32 Wonder Gecko's backup power domain. In this case, all
other power sources are removed from the kit, and only a small part of the EZR32 runs off the capacitor. It is also possible to enter
backup mode while the Board Controller is powered by selecting either BAT or USB with no battery in the socket or USB cable in the
connector.
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