A DC-DC switching converter device (101), in particular a quarter-brick or eighth-brick device having an industry standard pin out, comprises a pulse-width modulation circuit (132) for driving a power converting switch, a trim connector (109) for adjusting an output voltage of the device, where the device (101) is designed such that the pulse-width modulation circuit (132) is synchronizable to an external oscillator by an external synchronization signal applied to the trim connector. A DC-DC converting circuit comprises a plurality of DC-DC switching converters (101) featuring trim connectors (109) for adjusting output voltages of the converters (101), whereby the converters (101) are connected such that they share a common input bus. It further features a system EMI (electromagnetic interference) filter common to all the DC-DC switching converters (101) and an external oscillator delivering an external synchronization signal to the plurality of DC-DC switching converters (101). The external oscillator is designed such that a frequency of the external synchronization signal is higher than a free running frequency of each of the plurality of DC-DC switching converters (101). The external oscillator is connected to the trim connectors (109) of the DC-DC switching converters (101).