2 research outputs found
A 33-ppm/°C 240-nW 40-nm CMOS Wakeup Timer Based on a Bang-Bang Digital-Intensive Frequency-Locked-Loop for IoT Applications
This paper presents a wakeup timer in 40-nm CMOS for Internet-of-Things (IoT) applications based on a bang-bang Digital-intensive Frequency-Locked Loop (DFLL). A self-biased Σ Δ 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 Δ 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 mm2). 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°Cat 0.8-V supply).Accepted Author Manuscript(OLD)Applied Quantum Architecture
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Imepdance Sensing Techniques for Integrated Circuits Sensor Applications
Impedance measurements are increasingly demanded in modern CMOS sensing systems as impedance is the most common electrical signal obtained from sensors, delivering physical, chemical and biomedical quantity changes. Impedance sensing for wide interested frequency, broad dynamic range, and various sensor interfaces has numerous challenges, especially targeted in CMOS miniaturization with power and area limitation. In this thesis, first, a low power impedance-based cytometer architecture for cell analysis applications is presented. Fabricated in 0.18μm CMOS process with 6pArms input-referred noise over 200Hz bandwidth at 0.5 MHz modulation frequency, the impedance sensor demonstrates in detecting 3μm diameter particles. Secondly, using impedance sensing technique, a low-power RC oscillator based on IQ-balanced impedance sensing FLL is designed and demonstrated, achieving 25.4ppm/°C across temperature variation and 0.27%/V across supply variation at 650kHz output frequency