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This paper presents a delta-sigma control loop for a buck-boost DC-DC converter with fractional gains. The charge pump used to convert the input voltage acts as a D/A converter in the loop, and its output ripple is frequency shaped by the loop, which also provides the pulse frequency modulation needed for the conversion. Simulation results show that the delta-sigma loop results in spreading the tones in the frequency domain. A suppression of up to 50 dB is observed in the 0-20 kHz range.