This research is part of the nanotera.ch project Intelligent Integrated Systems for Personalized Medicine (ISyPeM).
|Reconfigurable CMOS Biosensor Front-end
The objective of this research work is to realize a flexible and versatile low power CMOS sensor interface aimed at biomedical applications. The interface is used to sense incoming electrical signals from the electrochemical biosensors present as an implant or a patch in the human body to monitor physiological parameters and drug concentration. From a design viewpoint, the interface needs to be: 1. Flexible and Reusable for sensing low level electrochemical signals which can be either current or voltage. 2. Low power due to the size and power constraints of the application. 3. Low Noise Figure (particularly at low frequencies due to low frequency input signals (< 1 Hz – 100 Hz)). In this research work, a low noise transimpedance amplifier is used for sensing current signals and a chopper based instrumentation amplifier is used for sensing voltage inputs. The frontend is followed by a reconfigurable ADC designed using asynchronous techniques to take advantage of its low power features.
Asynchronous A/D converters use amplitude quantization instead of the conventional time quantization in sampling based A/D converters and the benefits are activity dependant power consumption, power savings due to the absence of a sampling clock and improved SNR by virtue of backend asynchronous digital filtering. In the presence of a digital filter, the SNR of the ADC improves by approximately 3 dB for every digital bandwidth reduction by a factor of 2. Among the different asynchronous ADC architectures, asynchronous delta modulation based ADC is used as part of this work.