Startup techniques for 95 mV step-up converter by capacitor pass-on scheme and ${\rm V} _{\rm TH}-Tuned oscillator with fixed charge programming

This paper presents a 95 mV startup-voltage step-up DC-DC converter for energy harvesting applications. The capacitor pass-on scheme enables operation of the system from an input voltage of 95 mV without using additional off-chip components. To compensate for the die-to-die process variation, post-fabrication threshold voltage $({\rm V}-{\rm TH})$ trimming is applied to reduce the minimum operating voltage $({\rm V}-{\rm DDMIN})$ of the oscillator. Experimental results demonstrate the 34% ${\rm V} _{\rm DDMIN} reduction of the oscillator by post-fabrication ${\rm V} _{\rm TH} trimming. The proposed step-up converter achieves the lowest startup voltage in standard CMOS without using a mechanical switch or large transformer.