A 120nW 18.5kHz RC oscillator with comparator offset cancellation for ±0.25% temperature stability

Integrated low-frequency oscillators can replace crystal oscillators as sleep-mode timers to reduce the size and cost of wireless sensors [1]. Since the timer is one of the few continuously functioning circuits, minimizing its power consumption can greatly reduce sleep-mode power of highly duty-cycled systems. Temperature stability of the oscillator is important in order to minimize timing uncertainly and guard time for the radios, and thus maximizing sleep time. The voltage-averaging feedback method described in [2] achieves high stability in the MHz frequencies, but when scaled to the kHz range, requires very large filters. On the other extreme, gate leakage-based timers have been designed for sub-nW power consumption, but operate in the sub-Hz frequencies [3]. In the past, high accuracy RC oscillators in the kHz range have been designed with feed-forward correction [1] and self-chopped operation [4]. In this work, an offset cancellation architecture achieves long-term frequency stability and temperature stability while operating at lower power

A CMOS blood cancer detection sensor based on frequency deviation detection

This paper proposes a technique to detect Leukaemia (blood cancer) based on the frequency modulation of a relaxation oscillator by changes in the dielectric constant of blood cells. A novel 16-bit frequency detector with a digital output has been proposed to detect the frequency difference between two oscillators based on healthy blood and Leukaemic blood. A circuit has been designed, to operate on a 1.2V supply, post layout simulations shows 0.35mA current consumption. The chip Area including pads~0.6mm∗0.45m

Ultra-low Power Circuits for Internet of Things (IOT)

Miniaturized sensor nodes offer an unprecedented opportunity for the semiconductor industry which led to a rapid development of the application space: the Internet of Things (IoT). IoT is a global infrastructure that interconnects physical and virtual things which have the potential to dramatically improve people's daily lives. One of key aspect that makes IoT special is that the internet is expanding into places that has been ever reachable as device form factor continue to decreases. Extremely small sensors can be placed on plants, animals, humans, and geologic features, and connected to the Internet. Several challenges, however, exist that could possibly slow the development of IoT. In this thesis, several circuit techniques as well as system level optimizations to meet the challenging power/energy requirement for the IoT design space are described. First, a fully-integrated temperature sensor for battery-operated, ultra-low power microsystems is presented. Sensor operation is based on temperature independent/dependent current sources that are used with oscillators and counters to generate a digital temperature code. Second, an ultra-low power oscillator designed for wake-up timers in compact wireless sensors is presented. The proposed topology separates the continuous comparator from the oscillation path and activates it only for short period when it is required. As a result, both low power tracking and generation of precise wake-up signal is made possible. Third, an 8-bit sub-ranging SAR ADC for biomedical applications is discussed that takes an advantage of signal characteristics. ADC uses a moving window and stores the previous MSBs voltage value on a series capacitor to achieve energy saving compared to a conventional approach while maintaining its accuracy. Finally, an ultra-low power acoustic sensing and object recognition microsystem that uses frequency domain feature extraction and classification is presented. By introducing ultra-low 8-bit SAR-ADC with 50fF input capacitance, power consumption of the frontend amplifier has been reduced to single digit nW-level. Also, serialized discrete Fourier transform (DFT) feature extraction is proposed in a digital back-end, replacing a high-power/area-consuming conventional FFT.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137157/1/seojeong_1.pd