A single-inductor three-output boost DC-DC converter was designed. The converter adopted the average current mode with the output voltages of all branches being linearly added to form the common-mode feedback signal for loop compensation. A switch capacitor sampling network was proposed. The output voltage was sampled, and the sampled voltage was compared with the reference voltage to correct the DC offset between the output voltage and the reference voltage. To suppress the cross-regulation among output branches, a novel energy control logic circuit was proposed, which could realize the cyclic charging of each output branch within a single inductor charge-discharge cycle. The boost converter was designed in a 0.18 μm CMOS process. The simulation results show that the first two output branches suffer from no cross-regulation and the impact on the third output branch can be effectively alleviated with a 100 mA load transient change.