Multi-Channel High-Dynamic-Range Implantable VCO-Based Neural-Sensing System

Speaker: Wenlong Jiang
Affiliation: Ph.D. Candidate - UCLA

Abstract:  Neuromodulation, which is sending electrical pulses into the brain, is an alternative treatment method on neuropsychiatric disorders when traditional methods, such as surgery or medication, fail. However, current neuromodulation systems are insufficient. The channel number is very limited leading to a low stimulation precision; the system is doing open-loop stimulation, not allowing on-the-fly optimization of the stimulation for long-term treatment. Future neuromodulation system needs to be a multi-channel, closed-loop platform that can provide high spatial precision and can automatically adjust the stimulation pattern based on the sensed brain state. The multi-channel, closed-loop system poses new requirements on the brain sensing circuit and system design. The sensing circuit needs to provide large input range for concurrent stimulation and sensing in the closed-loop system and provide a reliable interface for the device/patient safety under the implant power constraint. Current state-of-the-art is not capable of meeting all these requirements.

In this talk, we are going to present a VCO-based neural sensing front-end circuit that converts the input voltage into the phase domain and performs the direct digitization. The phase-domain processing allows large input range which can contain both the stimulation artifact and the neural signals. Several techniques have been proposed to battle the challenges in the design: a multi-rate duty-cycled resistor is adopted as a reliable solution in the high pass filter for the safe brain-machine interface; chopping is applied inside the VCO to lower circuit noise and a new glitch-free quantizer is designed at the analog-digital interface; the circuit linearity is restored by the digital non-linearity correction post digitization. With these techniques, the design achieves 10× linear range and 2-3 bit ENOB improvement over state-of-the-art with comparable power and noise performance.

A 32/64-channel sensing chip with this front-end is also going to be present with the integration into a miniaturized PCB. The sensing performance and function have been verified at bench-top and in-vitro, under the setting of concurrent stimulation and sensing. It allows the further development of a complete multi-channel closed-loop neuromodulation implant.

Biography: Wenlong Jiang received the B.E. degree in electronic engineering from Tsinghua University, Beijing, China, in 2009, and the M.Sc. degree (cum laude) in electrical engineering from Delft University of Technology, Delft, The Netherlands, in 2011. He is currently pursuing the Ph.D. degree with the Department of Electrical Engineering, University of California, Los Angeles. His current research interests include analog, mixed-signal, and RF circuit and system design. He received the Graduate Division Fellowship in UCLA from 2012 to 2013.

For more information, contact Prof. Dejan Markovic ()

Date(s) - Aug 22, 2017
11:00 am - 1:00 pm

E-IV Tesla Room #53-125
420 Westwood Plaza - 5th Flr., Los Angeles CA 90095