Mixed-Signal CMOS Circuits

The continously growing density of CMOS circuits allows for integration of increasing functionality within the same space, which greatly benefits digital and mixed-signal CMOS circuits. The additional capabilities can be used to introduce control circuits on top of the functional layers, which enable reconfiguration of components during runtime. By using such flexible and generalized approach, many discrete functionalities can be integrated to the same circuit and the whole system benefits from component reuse. One disadvantage of shrinking technologies is the proportionally increasing need of precision and controllability in manifacturing. As both of them are getting more and more limited due to natural circumstances, mismatches in integrated circuits occur e.g. variations in width, length and doping of MOSFETs. While such mismatches can be neglected in the range of multiple µm, their influence greatly worsens in technology sizes of less than 100nm.

Our research on mixed-signal CMOS circuits focuses mainly on two fields. The field of research on runtime reconfigurable systems emphasizes both analog and digital circuits. The focus is to implement intelligent reuse and variable wiring of suitable parts both for rapid prototyping and also flexible implementations. In contrast to application specific integrated circuits, our reconfigurable systems are adaptable to various constraints during deployment in the field.

The focus of our second field is to utilize manifacturing induced mismatch to implement so-called Physical Unclonable Functions. The working principle of such PUFs is that a unique and non-reproducable behavior based on mismatch can be achievied by custom designed circuits. This emerging research field promises great benefit for hardware cryptograhpic systems and has gained increasing interests over the last two decades.

Projects

Physical Unclonable Functions (PUFs)

A. Herkle: Over the last decade, Physical Unclonable Functions (PUF) became a topic of increasing interest in cryptographic and authentication applications. Utilizing physical variations in the silicon resulting from limited fabrication accuracy, PUFs offer great characteristics for this field namely uniqueness, unpredictability and unclonability. When stimulated with a digital input, they generate an individual digital response based on their unique mismatches ... [ mehr]


Field Programmable Analog Arrays (FPAAs)

J. Becker: Many attempts have been made to apply rapid-prototyping techniques known from the digital domain to analog designs. The goal of the presented work is to develop an FPAA, which is suitable for reconfigurable implementation of analog continuous-time (CT) high-frequency filters on an integrated circuit ... [more]