CCM/GM relative skip energy control in single-inductor multiple-output DC-DC converter for wearable device power solution

Compact size wearable devices require multiple supplies with relative large loading difference, which causes serious cross regulation, large ripple and oscillation in single-inductor multiple-output (SIMO) DC-DC converter. Thus, a continuous conduction mode/green mode (CCM/GM) relative skip energy control (RSEC) in single-inductor multiple-output (SIMO) is proposed for wearable device power solution. Different from conventional absolute skip method, the RSEC eliminates unnecessary skip-induced voltage ripple and cross regulation with well regulation performance over wide load and voltage ranges. Optimization between efficiency and voltage ripple achieves low noise supply and reduced switching loss. Moreover, smooth transition between CCM and GM provides high power and longer usage time in wearable devices. The test chip fabricated in 0.18μm CMOS process occupies 2.24mm² active area. Maximum output ripple, overshoot/undershoot and cross regulation are kept below 17mV, 27mV and 0.0432mV/mA, respectively.