A 14.4nW 122KHz dual-phase current-mode relaxation oscillator for near-zero-power sensors

This paper presents a Power Management Unit (PMU) powered by a 1 mm 2 solar cell on the same substrate to rise up the harvested voltage above 1.1 V. The on-chip solar cell and the PMU are fabricated in standard 0.18 μm CMOS technology achieving a form factor of 1.575 mm 2. The PMU is able to start up from a harvested power of 2.38 nW without any external kick off or control signal. The PMU features a continuous and two-dimensional Maximum Power Point Tracking (MPPT) working in open-loop mode to handle a harvested power range from nW to μW, by modifying both the charge pump topology and the switching frequency. The MPPT is based on four voltage level detectors that define five working regions depending on the illumination and on a self-tuning reference current for a fine adjustment of the switching frequency. The chip also includes an auxiliary charge pump to generate the voltage level necessary for the control circuit, implemented as a Pelliconi charge pump of 8 stages with NMOS transistors in Pwell as diodes. A Dickson charge pump with transmission gates as switches and with variable gain and capacitance per stage is also designed as the main charge pump. Finally, two relaxation oscillators are implemented to drive both charge pumps. This paper is accompanied by a video file demonstrating the PMU operation by powering an off-chip NAND gate.

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“…The main oscillator consists of a relaxation oscillator based on [31] with a variable oscillation frequency. As Fig.…”

Section: Oscillatorsmentioning

confidence: 99%

“…The auxiliary oscillator in Fig. 10 is a relaxation oscillator with the same topology introduced in [31]. In our case, we have adjusted the dimensions of the transistors for very low power applications and the oscillating frequency is controlled by only the same V BIAS as in the main oscillator, designed to vary from 1.5 kHz to 500 kHz.…”

Section: Oscillatorsmentioning

confidence: 99%

Micro-Energy Harvesting System Including a PMU and a Solar Cell on the Same Substrate With Cold Startup From 2.38 nW and Input Power Range up to 10 $\mu$W Using Continuous MPPT

Ferro

Brea

López

et al. 2019

IEEE Trans. Power Electron.

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“…This increases timer's cost and module size, which are critical for many IoT applications. As a result, fully-integrated RC oscillators are usually preferred for those applications [4]- [19].…”

Section: Introductionmentioning

confidence: 99%

A 33-ppm/°C 240-nW 40-nm CMOS Wakeup Timer Based on a Bang-Bang Digital-Intensive Frequency-Locked-Loop for IoT Applications

Ding

Zhou

Traferro

et al. 2020

IEEE Trans. Circuits Syst. I

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This paper presents a wakeup timer in 40-nm CMOS for Internet-of-Things (IoT) applications based on a bangbang Digital-intensive Frequency-Locked Loop (DFLL). A selfbiased Σ∆ Digitally Controlled Oscillator (DCO) is locked to an RC time constant via a feedback loop consisting of a single-bit chopped comparator and a digital loop filter, thus maximizing the use of digital circuits while keeping only the RC network and the comparator as the sole analog blocks. Analysis and behavior level simulations of the DFLL have been carried out to guide the optimization of the long-term stability and frequency accuracy of the timer. High frequency accuracy and a 10× enhancement of long-term stability is achieved by the adoption of chopping to reduce the effect of comparator offset and 1/f noise and by the use of Σ∆ modulation to improve the DCO resolution. Such highly digitized architecture fully exploits the advantages of advanced CMOS processes, thus enabling operation down to 0.7 V and a small area (0.07 mm 2). The proposed timer achieves the excellent energy efficiency (0.57 pJ/cycle at 417 kHz at 0.8-V supply) over prior art while keeping excellent on-par long-term stability (Allan deviation floor <20 ppm) and temperature stability (33 ppm/ o C at 0.8-V supply).

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“…RC relaxation oscillator is one of the most common structures without external components [1]. Most of the relaxation oscillators are based on current mode [2] or voltage mode [3][4][5].…”

mentioning

confidence: 99%

“…Recently, some offset cancellation and delay compensation techniques have been proposed. Capacitor resetting delay is eliminated by dual-phase operation in a current mode oscillator [2]. A comparator offset cancellation technique by switching the comparator input polarity every half cycle was proposed in [3].…”

mentioning

confidence: 99%

Integrated relaxation oscillator with no comparator for energy harvesting

Wang

Zhang

et al. 2017

Electron. lett.

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A fully-integrated 12 kHz relaxation oscillator for energy harvesting application is presented. The oscillator has no comparator and no reference voltage. A conventional comparator has been replaced by a pseudo-inverter chain to avoid comparator offset effect. Moreover, inverter threshold variation has no impact on the frequency. The circuit has been designed with 0.18 µm standard CMOS process. The oscillator operates in subthreshold region and consumes an ultra-low power of 120 nW. A temperature coefficient of 31 ppm/°C has been achieved over −40 to 90°C.

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A 14.4nW 122KHz dual-phase current-mode relaxation oscillator for near-zero-power sensors

Cited by 38 publications

References 7 publications

Micro-Energy Harvesting System Including a PMU and a Solar Cell on the Same Substrate With Cold Startup From 2.38 nW and Input Power Range up to 10 $\mu$W Using Continuous MPPT

Micro-Energy Harvesting System Including a PMU and a Solar Cell on the Same Substrate With Cold Startup From 2.38 nW and Input Power Range up to 10 $\mu$W Using Continuous MPPT

A 33-ppm/°C 240-nW 40-nm CMOS Wakeup Timer Based on a Bang-Bang Digital-Intensive Frequency-Locked-Loop for IoT Applications

Integrated relaxation oscillator with no comparator for energy harvesting

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