This article presents a power management unit
(PMU) enabling ultra-wide power-performance tradeoff well
beyond voltage scaling, and adaptation to the sensed power/
energy availability in the harvester and battery. Gap-less power
scaling by more than five orders of magnitude and down to
nW permits continuous microcontroller unit (MCU) operation
regardless of the battery energy availability, thanks to a sub-mm2
on-chip harvester. Such battery-indifferent operation allows to
considerably shrink the battery down, as battery discharge no
longer has disruptive impact on operation. Battery-indifferent
operation is enabled by introducing a purely harvested power
mode in the PMU, and widely power-scalable circuits in critical
blocks to maintain the power efficiency nearly constant down to
nW level. To avoid pessimistic power/timing overdesign, a novel
self-biasing comparator and a zero current switching scheme
with fast convergence and circuit sharing across power modes
are proposed. A 180-nm testchip shows MSP430-like MCU power
scaling from sub-mW down to 1.85 nW, with at least 27× power
dynamic range extension compared to prior art. Self-start-up
from 2-nW harvested power is demonstrated, corresponding
to a 0.8-mm2 on-chip solar cell with 100-lx illuminance (i.e.,
equivalent to a very dark overcast day).

Researcher/Author: Longyang Lin, Saurabh Jain and Massimo Alioto

IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 55, NO. 4, APRIL 2020; https://ieeexplore.ieee.org/document/8945241 

In this work, voice activity detection (VAD) system
with dynamic energy-quality (EQ) scalability is presented. EQ
scalability is enabled through the insertion of multiple knobs at
different levels of the signal chain, starting from analog-digital
conversion and ending at the classification stage. Such knobs are
co-optimized at runtime to achieve a given quality target with
minimal energy. Such co-optimization is also shown to improve
the fit of the machine learning algorithm, allowing for more
graceful quality degradation. The proposed system, fabricated on
a 28nm test chip, classifies at 81.2% accuracy while consuming
51.9 nJ/frame in a 10dB noise context. Scaling up energy
consumption by 3.5x improves accuracy by 5.2%.

Researcher / Author: Jinq Horng Teo, Shuai Cheng and Massimo Alioto

IEEE (2019), 978-1-7281-0996-1/19; https://ieeexplore.ieee.org/document/8964767

The healthcare system is undergoing a noticeable transformation from a reactive, post-disease
treatment to a preventive, predictive continuous healthcare. The key enabler for such a system is
a pervasive wearable platform. Several technologies have been suggested and implemented as a
wearable platform, but these technologies either lack reliability, manufacturing practicability or
pervasiveness. We propose a screen-printed circuit board on bio-degradable hydrocolloid dressings,
which are medically used and approved, as a platform for wearable biomedical sensors to overcome the
aforementioned problems. We experimentally characterize and prepare the surface of the hydrocolloid
and demonstrate high-quality screen-printed passive elements and interconnects on its surface using
conductive silver paste. We also propose appropriate models of the thick-film screen-printed passives,
validated through measurements and FEM simulations. We further elucidate on the usage of the
hydrocolloid dressing by prototyping a Wireless Power Transfer (WPT ) sensor and a humidity sensor
using printed spiral inductors and interdigital capacitors, respectively.

Researcher / Author: Haneen Alsuradi and Jerald Yoo

Scientific Reports (2019), 9:17467; https://doi.org/10.1038/s41598-019-53033-4

This paper proposes a 15-Ch. low power, small area, Orthogonal Code Chopping Instrumentation Amplifier (OCCIA). Orthogonal codes directly modulate each channel and merge into a single IA while performing dynamic offset compensation. Digitization-Before-Demodulation (DBD) transmits the combined data directly, which alleviates ripple noise, and completely removes the demodulation and TX encoding overhead from the SoC. The proposed OCCIA SoC in 0.18μm 1P6M CMOS achieves the lowest gain mismatch (0.43%) among recent multi-channel IAs with one of the smallest areas (0.019mm2/ch.) while consuming 1.97μW/ch. and low crosstalk (<- 53.5dB) at 490Hz bandwidth.Researcher /

Author: Jeong Hoan Park, Tao Tang, Lian Zhang, Kian Ann Ng and Jerald Yoo

IEEE Asian Solid-State Circuits Conference, 21-1 (7071); https://onlinelibrary.wiley.com/doi/abs/10.
1002/adma.201805921

Intracardiac echocardiography (ICE) is an ultrasound sonogram that visualizes the anatomical structure of the heart in real time, with a mm-scale catheter inserted through the intracardiac vessels, and guides surgical intervention for atrial septal defect (ASD) closure. To achieve high-quality medical imaging, an ICE system must meet stringent power consumption requirements with low-noise operation. Since an ASIC and ultrasound transducers are tightly bonded through flip-chip or direct integration, an ultrasound unit TRX channel must be pitchmatched to each transducer channel [1,2]. A piezoelectric Micromachined Ultrasound Transducer (pMUT) is a suitable ultrasound transducer for implantable sensor applications, since it does not need high (~200V) bias that is a must in capacitive MUTs (cMUT) [3]. However, pMUT devices suffer from process variation, which leads to low image quality, and to date, no work addresses this issue for both TX/RX in real time. To meet all these requirements at once, we present a 6×6 TRX pitch-matched pMUT ASIC with a standard CMOS-compatible 13.2V HV pulser, on-chip per-pixel calibration scheme, and a Dynamic Bit-Shared (DBS) ADC for portable ICE applications.

Researcher/Author: Jihee Lee, Kyoung-Rog Lee, Ben Eovino, Jeong Hoan Park, Liwei Lin, Hoi-Jun Yoo and Jerald Yoo

2019 IEEE International Solid- State Circuits Conference – (ISSCC); https://ieeexplore.ieee.org/document/8662531