The design of a low-power low-voltage programmable temperature detection circuit is described. The circuit provides a digital output that signals over-temperature and undertemperature conditions when die temperature rises above or falls below the programmed temperature thresholds. The output is obtained from the comparison between two temperaturerelated signals; the former has a CTAT with fixed thermal coefficient and the latter has an adjustable (PTAT, ZTAT or CTAT) thermal coefficient. The circuit design employs current as the main variable, based on the concept of inversion level. The circuit has been implemented in a 0.25µm standard CMOS process, operates down to 1.5V, occupies an area of 0.0235mm 2 , consumes 750nA including bias circuitry, and has ±5% accuracy for threshold temperatures ranging from -40 o C to 150 o C.

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Voltage references and temperature sensors are blocks extensively used in microelectronic systems. As an alternative to the use of consolidated structures that are protected by intellectual property agreements, there is a permanent demand for the development of new techniques and structures for these circuits. It can be also highlighted the growing interest for low-voltage and low-power solutions, implemented in conventional IC technologies. This work describes the development of a circuit that meets these requirements by providing a voltage reference and temperature sensing signal obtained from a suitable arrangement of MOS transistors biased in strong inversion.The operation principle of the circuit developed is based on the concept that it is possible for a stack of n MOS transistors, biased by an appropriate current, to show a voltage drop, equal to nV GS , with the same thermal variation rate as a V GS voltage produced by a single transistor. Hence, the difference between the two voltage signals is temperature independent, characterizing a voltage reference. However, the stacking of two or more transistors prevents the operation of the circuit under low voltage. This fact motivated to adapt the technique by obtaining the voltage nV GS with the aid of an array of resistors and no stacked transistors. The minimum supply voltage becomes limited only by the reference voltage itself, whose amplitude is close to a single V GS . The circuit developed also provides a voltage signal almost linearly dependent with the absolute temperature, which can be applied for thermal sensing.Prototypes corresponding to various dimensional versions of the circuit were produced to experimentally verify the principle of operation. The best performance corresponds to the generation of a voltage reference signal with 8.7ppm/ºC thermal coefficient, from -40ºC to 120ºC, under a 1V supply voltage. Although the state of the art is represented by values as low as 1ppm/ºC, at the same temperature range, the circuit's compact aspect together with the possibility to attend low-voltage and low-power requirements grants it value as contribution to this field of research and development.ix AgradecimentosÀs instituições UNICAMP, CTI e Freescale Semicondutores do Brasil.À CAPES pelo apoio financeiro.Aos amigos do laboratório, que foram também meus professores, colegas e companheiros de divertimento, e que tanto contribuíram para a realização deste trabalho.Ao meu orientador, Prof. Dr. Carlos Alberto dos Reis Filho, cujo entusiasmo e paixão pela microeletrônica me contagiaram ao ponto de eu mesmo me apaixonar pela área. Ao Prof. Rezende, pela preciosa convivência, que "dito de forma muito simples", foi como um divisor de águas.À minha família, de sangue e coração, pelo amor incondicional, sacrifício e entrega, a quem devo não apenas a possibilidade de concluir esta jornada, mas também a minha vida, minha saúde, meu futuro e minha felicidade.Às inúmeras pessoas que me ajudaram, cada um da sua maneira, a superar todas as barreiras e suportar as tribu...