Fully Integrated Reconfigurable Solar Energy Harvester for $100\mu\mathrm{A}$ Burst Output Current Delivery with 78.6% Peak Energy Extraction Efficiency and Minimum Startup Incident Light Power of 0.27mW/cm2

The advancement in CMOS technology has facilitated the development of small form factor wireless sensing nodes, which can be coupled with energy harvesting (EH) for extending the operation lifetime. Even though the system power in energy-constrained EH wireless sensing nodes can be in the
$10\mu\mathrm{A}$
and even down to the
$\text{sub}-\mu\mathrm{A}$
level [1]–[2], the peak current consumption during data transmission can increase up to
$100\mu\mathrm{A}\text{and}$
more [3]. To resolve this problem, prior works typically require a bulky off-chip storage capacitor for providing the peak output current (up to
$50\mu\mathrm{F}$
for 2mA in [4]), as shown in Fig. 1. Despite the inevitable increase in system volume and cost, such an approach also suffers from a poor energy utilization (only ~2% of the energy stored is extracted). Although the counter-flow switched-capacitor (SC) reconfiguration approach in [5] can achieve a peak energy extraction efficiency (EEE) of up to 70% using on-chip capacitors, the requirement of a stable voltage source can limit its application in EH systems, as the power generated from EH sources are highly dependent on the ambient condition. This work presents a fully-integrated single-chip solar EH system, which employs on-chip solar cells and a capacitive EH interface for generating a stable
$\mathrm{V}_{\text{out}}$
of 0.85V with a
$\mathrm{V}_{\mathrm{i}\mathrm{n}}$
of 0.325~0.5V, featuring a high power conversion peak efficiency (PCE) of 79.3%. It can also provide an
$\mathrm{l}_{\text{out}}$
of
$\sim 100\mu\mathrm{A}$
using only
$8\times 400\text{pF}$
on-chip capacitors, with a peak EEE of 78.6%.