An error-based control method is proposed for a single-inductor multiple-output (SIMO) converter that maintains high efficiency under various load conditions. A peak efficiency of 88.7% was achieved with one output (I-O1) of 5 mA, while the other outputs are at 432 mA. A hybrid topology composed of a switching converter and a linear regulator is also presented for fast load transient response. The proposed SIMO buck converter was fabricated with a 1P4M 0.35 mu m BCD process and has 10 independently regulated outputs. The measured load transient waveform shows cross regulation of 0.1 mV/mA and a load transient of 0.17 mV/mA. This was achieved under load transient conditions for one output (I-O9) in between 1 mA and 100 mA with the other outputs at 422 mA.