LDO-Assisted Voltage Selector Over 0.5-to-1V VDD Range for Fine Grained DVS in FDSOI 28nm with 200ns/V Controlled Transition

This paper presents a 95% power-efficient duty-cycled LDO-assisted voltage selector (LAVS) for fine grained spatial and temporal voltage scaling in FDSOI 28nm technology. LAVS enables 200ns/V controlled transitions between three power rails over a 0.5-to-1V range while maintaining the digital activity of the supplied load. During transitions, current and voltage detections are proposed to protect power rails from reverse current. LAVS has a 13% Si area overhead to drive a 0.2 mm2 digital load. Thanks to a 100MHz-bandwidth LDO, which is only enabled during transition to save power consumption, the voltage selector also maintains a smooth voltage transition even if a digital load suddenly changes its activity factor (4mV/mA load transient). LAVS achieves 30pJ energy dissipation per voltage transition which is negligible compared to the power consumed by the digital load (50mW@0.2mm2). This therefore allows a MHz dynamic voltage scaling rate.