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a b s t r a c tThe concept of time-domain reference-ladder for the implementation of fully-digital flash-ADCs is proposed in this work. The complete reference ladder is implemented using only digital circuits. Based on this concept, a flash ADC is proposed and implemented in this work using digital circuits, one comparator and a customized sample-and-ramp circuit. An unconventional time-to-digital conversion (TDC) technique is introduced which performs the complete conversion within a single clock cycle. The measurement results show that the proposed 5-bit converter achieves an 80 MHz sampling rate while consuming 900 μW of power from the 1.8 V supply voltage. The prototype ADC is developed in a 180 nm standard CMOS technology and achieves the power efficiency of 445 fJ/conversion which is comparable to many existing state-of-the-art flash ADCs. The measured performance is achieved without any design optimization or circuit calibration techniques confirming the promising benefits of the proposed topology. Thanks to the fully-digital structure, the circuit enables a robust and compact implementation which is very convenient for interleaving and beneficial for many potential applications.

Current low temperature electronics (<175°C) with logical functions (CPUs, MCUs) have exceptional levels of reliability in terms of packaging, stemming from decades of research. However, electronics that operate at higher temperatures (>175°C) for prolonged periods of time require packaging technologies that have to tackle many new problems. At high temperatures traditionally used materials such as organic circuit boards, adhesives and standard solders degrade rapidly or undergo changes in structure and properties. An even more critical issue than high-temperature survivability is resistance to temperature cycling. Thermal mismatch between organic boards and semiconductor dies leads to high thermomechanical strains during swings from high to low temperature extremes, which can make an otherwise high temperature resistant assembly fail after a relatively low number of cycles. This work focuses on the packaging technologies for high temperature control modules, those with logical and signal conditioning applications. Although control modules share many similarities with power modules, they present their own unique design challenges, such as significantly higher complexity and a limitation of compatible materials. Here, recent research on substrates, die attach technologies and wirebond interconnects suited for high temperature ICs are presented along with packaging technologies for discrete components (capacitors and resistors) with the aim of identifying the current best solutions. Test vehicles for the various technologies were constructed and were subjected to high temperature storage at temperatures higher than 200°C. They were analysed in terms of degradation (i.e. loss in shear strength, pull strength, change in resistance, etc.). In parallel, a separate set of samples were subjected to temperature cycles from −20°C to 180°C and then analysed using the same tests as before for comparison. The combined data allow a recommendation to be made on how to assemble a viable control module such as one based on an SOI microcontroller designed at EPFL to operate at high temperatures.

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