An integrated DC-DC buck converter is an option on most Series 1 EFM32 and EFR32 devices. While this term is used across the EFM32/EFR32 documentation and often shortened to "DCDC", it's important to note that what's present on the chip still requires an inductor and a capacitor to generate the output voltage to which the DCDC is programmed.
In fact, what is actually seen on the VREGSW pin, which is an output from the MCU, is not the regulated voltage itself but the switching waveform associated with the DCDC. This waveform is, obviously, very different from what is seen at the actual output of the converter, which is the regulated voltage seen after the inductor and where the capacitor is connected to ground, e.g. the VDCDC node as shown in the figure below:
Programming of the DC-DC converter and device power configurations are covered in Application Note 0948: EFM32 and EFR32 Series 1 Power Configurations and DC-DC, but one item not addressed is the waveform seen on and voltage swing of the VREGSW pin. While the frequency can vary, the output waveform looks like this:
The voltage swing on VREGSW can vary, as well, including over temperature, but can be expected to range from -1V to VREGVDD + 1V, where the under/overshoot is due to the switching current flowing through the ESD/body diode during the DCDC powertrain's dead time.