New Chip Pushes the Power Efficiencies of Data-Converters

Data-converters bridge the physical analog world to the digital domain and are widespread in all electronic components around us—cell phones, cameras, displays, touch screens, wireless transceivers, health sensors, etc. But a longstanding limitation of data-converters is the presence electronic noise—it is one of the primary factors that causes data in the digital world to lose its original pristine quality. One way to lower noise is to burn more power, but that constrains the lifetime of portable devices. 

Chip micrograph

Researchers at the University of California San Diego led by electrical and computer engineering Prof. Drew Hall have developed a clever circuit technique termed 'OTA-stacking' to fundamentally improve the noise-power trade-off in analog to digital converters (ADCs). Their technique is based on the concept of current-reuse where N-fold stacking enables N times lower power for the same noise, which is very substantial. 

Somok Mondal

Their prototype chip achieves state-of-the-art performance in the hypercompetitive data-converter space and is being presented by UC San Diego electrical and computer engineering alumnus (Ph.D. '20) Somok Mondal on Feb. 17 at the International Solid-State Circuits Conference (ISSCC), 2021—the foremost global forum for presentation of advances in solid-state circuits and systems-on-a-chip.

Paper Title: 139μW 104.8dB-DR 24kHz-BW CTΔΣM with Chopped AC-Coupled OTA-Stacking and FIR DACs 

Authors: Somok Mondal, Omid Ghadami, and Drew A. Hall

ECE professor receives California grant for new project on brain research

Drew Hall, assistant professor of electrical and computer engineering at the Jacobs School.

Drew Hall, assistant professor of electrical and computer engineering, has been awarded a $120,000 seed grant from Cal-BRAIN, a California initiative aimed at revolutionizing our understanding of the brain.

Hall’s project will explore using magnetic nanoscale sensors, similar to those used in hard disk drives, to detect brain signals. These magnetic nanosensors provide an alternative to conventional brain monitoring methods, whose lifetimes are limited because of scar tissue formation.  

Applications of this work will increase the lifetimes of neural implants, which will ultimately lead to more effective, low-cost treatments for brain disorders. “There is a strong need for treatment methods of neurological diseases,” said Hall. The World Health Organization estimates that more than 50 million people worldwide suffer from epilepsy, and dementia continues to grow at the rate of 7.7 million new cases per year.

Currently, most brain monitoring methods measure the ionic current in the brain by making direct electrical contact with neurons (brain cells). This contact causes scar tissue to form around the electrodes, muffling the neural signals over time. Hall proposes measuring the magnetic field around the neurons instead. As a result, the magnetic nanosensors avoid direct physical contact with the neurons and are less sensitive to scar tissue formation.

“I’m excited about the team that we have put together to tackle this high-risk, high-reward research,” said Hall. The team is also led by Eric Fullerton, nanoengineering and electrical and computer engineering professor and director of the Center for Magnetic Recording Research, and Vikash Gilja, assistant professor of electrical and computer engineering.

Cal-BRAIN (the California Blueprint for Research to Advance Innovations in Neuroscience) is a statewide project jointly led by UC San Diego and the Lawrence Berkeley National Laboratory that was signed into law in June 2014. It is the California complement to the federal BRAIN Initiative announced by President Barack Obama in 2013. The 16 projects that were selected by Cal-BRAIN focus on developing new technologies to advance our ability to monitor and analyze brain activity. More information can be found at http://cal-brain.org/ and on the UCSD News story here.

Hall also received an NSF Engineering CAREER Award in March. See story here.