Design of high-resolution photodiode readout circuitry for a bio-implantable continuous glucose sensing chip

Glucose sensors are useful for monitoring and control of blood-sugar concentration for diabetic patients. There are many challenges in their wide-spread use and effectiveness in control of the disease. This work is a step towards achieving in vivo continuous long-term glucose monitoring using the optical near-infrared based glucose sensing principle. The thesis investigates and arrives at an architecture for the readout circuitry of such a sensor system. The goal is that the realized CMOS chip together with the optical sensing devices realized in Silicon-on-Insulator technology will form a single-implantable solution. The advantage is the long-term monitoring due to non-usage of chemical reagents. The thesis work addresses the read-out circuit requirements for a photodiode as part of such a sensor. The design of a high-resolution current-input sigma-delta ADC is discussed which targets to achieve 16-bit resolution for a photo-diode signal in the range of 100nA-10?A. Various optimizations for specifications such as noise, accuracy and energy-efficiency both at circuit and system level are addressed. The chip has been realized in a TSMC 0.18?m process. The initial measurements show the functionality of the ADC and its performance using the test set-up developed. A proof of concept of the optical-electrical interface with a photodiode shows the application of the circuit.

Subject

glucose sensor
incremental Sigma-Delta
current input ADC
dynamic reference
wide-dynamic range
sensor adaptable ADC

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http://resolver.tudelft.nl/uuid:ea9d2e1c-5b03-44e9-b916-587fd737313f

Embargo date

2014-01-01

Part of collection

Student theses

Document type

master thesis

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Thesis_Umanath_Final.pdf

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