Integrated State-of-Charge Circuit for Rechargeable Batteries

Acknowledgements I would like to thank all the people who have supported me in performing this research in any way. In particular, my thanks go to my direct supervisor Ronan van der Zee and my supervisors at SiTel Semiconductor, Wim Kruiskamp and Rene Beumer for their invaluable support and input during the entire cause of this work. I would also like to thank Bram Nauta and Rein Post for keeping up to date on the state of my research and for several interesting suggestions and remarks from their part. My final thanks go to all the people at the Hengelo Design Center, which is part of SiTel Semiconductor, for their support. Several of these people have had a particularly profound impact on my work, and I would like to thank them in particular. The foremost of these people is Lex Lubbers, who originally gave me a document with several project description, including this one. He has also given me invaluable information during the cause of this project, especially in the early design phase. The second person whom I would like to extend special thanks to is William Aartsen for his insights into charge pump design and device mismatch. Two other people to whom I owe special gratitude are Chris Smit and Jan Hovius, who have both helped me solve problems I had with Cadence on more than one occasion. In particular I would like to thank Chris for his patience when I was struggling with the AMS simulation (combined analog and Verilog simulation).Abstract The aim of this work is to create a low power system that can measure positive and negative voltages varying in magnitude from 100 µV to 100 mV with a relative accuracy of 1% or better. These voltages correspond to a current flow to or from a battery powering a DECT IC. Since these currents are quasi static, no accurate time domain representation is required, as long as the total charge is measured accurately. Since the system is constantly active and battery powered it needs to have a low current consumption. A maximum limit of 100 µA has been specified for this. The final result is a system that is based on converting the input voltage to a current using a differential pair with a low transconductance and continuously integrating this current. When the output voltage of the integrator reaches a certain threshold, a fixed amount of …