A 32-mV Supply Ring Oscillator Composed of Modified Schmitt Trigger Delay Cells for Integrated Start-Up Circuits in DC Energy Harvesting Systems

A 32-mV Supply Ring Oscillator Composed of Modified Schmitt Trigger Delay Cells for Integrated Start-Up Circuits in DC Energy Harvesting Systems

Implementing fully integrated start-up energy harvesting (EH) systems is very challenging. The most popular start-up circuit implementations use a low-voltage ring oscillator (RO). The characteristics of this RO rapidly deteriorate at VDD values below the transistor’s threshold voltage. A...

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Bibliographic Details
Main Authors: Mahmoud Ahmed, Aref Trigui, Sebastien Genevey, Yves Audet, Yvon Savaria
Format: Article
Language:English
Published: IEEE 2024-01-01
Series:IEEE Access
Subjects:
TEG
start-up techniques
ring oscillator
Schmitt trigger
cold start-up
dynamic body biasing
Online Access:https://ieeexplore.ieee.org/document/10676987/
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Summary:Implementing fully integrated start-up energy harvesting (EH) systems is very challenging. The most popular start-up circuit implementations use a low-voltage ring oscillator (RO). The characteristics of this RO rapidly deteriorate at VDD values below the transistor&#x2019;s threshold voltage. A novel delay cell based on a Schmitt trigger (ST) inverter leveraging dynamic body biasing (DBB) is proposed to mitigate this deterioration. The RO of the proposed cell, implemented in a 22 nm FD-SOI CMOS technology, is compared against conventional and state-of-the-art circuits implemented in the same technology. Simulated results show the proposed RO achieves the highest output swing and DC gain within the 40 to 100 mV supply voltage range. A prototype chip comprising a 27-stage RO was fabricated and tested in a 22 nm FD-SOI CMOS technology. When fed by a 50 mV supply voltage, this RO produces an output swing of <inline-formula> <tex-math notation="LaTeX">$\mathbf {80\%}$ </tex-math></inline-formula> of that voltage while oscillating at a 0.8 kHz clock frequency and consuming 300 pW. In reported experiments, oscillations started with VDD as low as 32 mV. To the authors&#x2019; knowledge, the proposed CMOS RO operates with the second-lowest ever reported supply voltage. Combining its low power and low area, this RO is most suitable for EH systems with restricted power and area budget.
ISSN:2169-3536

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