Integrated Solar Energy Harvesting and Storage Guilar, N.J.; Kleeburg, T.J.; Chen, A. ...
IEEE transactions on very large scale integration (VLSI) systems,
05/2009, Volume:
17, Issue:
5
Journal Article
Peer reviewed
Open access
To explore integrated solar energy harvesting as a power source for low power systems, an array of energy scavenging photodiodes based on a passive-pixel architecture for CMOS imagers has been ...fabricated together with storage capacitors implemented using on-chip interconnect in a 0.35-mum bulk process. Integrated vertical plate capacitors enable dense energy storage without limiting optical efficiency. Tests were conducted with both a white light source and a green laser. Measurements indicate that 225 muW/mm 2 output power may be generated by white light with an intensity of 20 kLUX.
Piezoelectric transducers are a viable way of harvesting vibrational energy for low power embedded systems such as wireless sensors. A proposed disk-shaped piezoelectric transducer with several ...electrodes enables increased energy harvesting from multiple mechanical resonances. To rectify the low-frequency AC voltage from harvested vibrational energy, a full-wave rectifier has been fabricated in 0.35 mum CMOS. Integrated peak selection circuitry allows input signals with 90deg relative phase shift from the multiple-electrode piezoelectric transducer to be rectified with reduced output ripple. The rectifier has a measured power efficiency of 98.3% while delivering 90 muW and occupying an area of 0.007 mm 2 . This high efficiency further enables energy harvesters to power wireless devices for extended durations.
Integrating energy-harvesting photodiodes with logic and exploiting on-die interconnect capacitance for energy storage can enable new, ultraminiaturized wireless systems. Unlike CMOS imager pixels, ...the proposed photodiode designs utilize p-diffusion fingers and are implemented in a conventional logic process. Also unlike specialized solar cell processes, the designs utilize the on-chip metal interconnect to form a diffraction grating above the p-diffusion fingers which also provides capacitive energy storage. To explore the tradeoffs between optical efficiency and energy storage for integrated photodiodes, an array of photovoltaics with various diffractive storage capacitors was designed in a 90-nm CMOS logic process. The diffractive effects can be exploited to increase the photodiodes' response to off-axis illumination. Transient effects from interfacing the photodiodes with switched-capacitor DC-DC converters were examined, with measurements indicating a 50% reduction in the output voltage ripple due to the diffractive storage capacitance. A quantitative comparison between 90-nm and 0.35-μm CMOS logic processes for energy-harvesting capabilities was carried out. Measurements show an increase in power generation for the newer CMOS technology, however at the cost of reduced output voltage. One potential application for the integrated photodiodes is harvesting energy for a subdermal biomedical device.
A passive CMOS switched-capacitor finite-impulse-response equalizer is described. A sampling rate of 200 MS/s is achieved by six time-interleaved channels. Nonlinear parasitic capacitance scales the ...equalized output but does not affect the zero locations of the equalizer for a binary or ternary data signal. The 4-tap equalizer prototype is fully differential. At 200 MS/s, the equalizer dissipates 19.5 mW, which is virtually all consumed by clock drivers, and occupies an active area of 1.3 mm 2 in a 0.35 mum CMOS process
A low-power passive switched-capacitor finite-impulse response equalizer with six time-interleaved channels has been fabricated in 0.35/spl mu/m CMOS. Nonlinear parasitic capacitance scales the ...equalized output but does not affect the zero locations of the equalizer for a binary or ternary data signal. The equalizer is fully differential with a 4-tap transfer function. The equalizer consumes 19.5 mW at 200 MS/s and occupies an active area of 1.3mm/sup 2/.
Wireless sensors and implantable medical devices have driven IC design to extremes of low power consumption to maximize system operating lifetimes from fixed energy stores or from energy harvested ...from the environment. Reaching the limits of miniaturization will require approaching the limits of power dissipation. We describe three key sensor subsystems: integrated diodes for solar energy harvesting, efficient microwatt power conversion circuits, and supply-voltage-ripple-tolerant digital circuits. We then extrapolate from these examples to find the minimum surface area and volume required for energy harvesting sensors.
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