Low-Cost Low-Power Time Domain High Accuracy Temperature Sensors and Its Application(I)

[[abstract]]廉價之高效能溫度感測器的需求與日俱增，除了價格與功能的考量之外，在現今系統越來越複雜之趨勢以及可攜式之應用，低功率之溫度感測電路實是不可或缺。傳統的電壓域溫度感測器，其溫度轉換至電壓之轉換特徵曲線皆存在有相當曲率以及運算放大器(OPAMP)的偏移電壓的問題，因此為了減少誤差，此溫度感測器需要額外的校正電路來減少誤差而造成晶片面積及功率消耗的增加，再則以溫度解析度優於0.1°C之電路為例，通常需要使用超過10位元以上之DAC或 ADC，如此往往會佔據更大的面積以及消耗更多的功率而逐漸不適用於可攜式系統甚至於難以整合於系統晶片或是超大型積體電路。為了符合可攜式系統之低成本及低功耗需求，本計劃預計採用由反相器延遲線組成之新式溫度感測技術，以時域取代傳統之電壓域來實現精簡之電路架構，無需額外之校正電路與雷射修整程序亦可獲得高精確度。本研究團隊先前利用已成功驗證此新型時域溫度感測電路，然而該創新電路依然有相關改善空間，諸如解析度之提升，誤差之降低，面積之改善等等。本計劃第一年預計提升時域溫度警示調節電路之整體效能，使之更適用於高精度、低成本及低功耗之可攜式應用，將有兩個版本晶片被實現，預計規格為 0.1°C 解析度、溫度誤差優於±0.3°C 以及功率消耗小於30μW；第二年則擴充此溫度警示電路之應用，結合SAR 控制邏輯以實現智慧型溫度感測器(Smart Temperature Sensor)，預計規格為0.04°C 解析度、溫度誤差優於±0.3°C 以及功率消耗小於5μW。[[abstract]]The market for temperature sensors has become tremendously large. Low-cost and low-power temperature sensors are always required to meet the needs of the mainstream market and further apply in portable application. Moreover, the systems are getting more and more complex and fast. It is necessary to save on power consumption, particularly in smart temperature sensor sub-systems. Conventional voltage-domain temperature sensors usually utilize BJT-based circuits for temperature sensing, and rely on ADCs or DACs, which occupy a large chip area and consume much power. To improve accuracy and stability, the additional on-chip calibration circuits are used in both temperature sensors and ADCs or DACs at the expense of a further increase in cost and power. Moreover, to achieve the resolution of 0.1°C, either the chip area would become larger or the circuits more complicated, making the smart temperature sensors less applicable to low-cost portable applications and even less suitable for SOC or VLSI integration. To achieve low-cost and low-power in portable systems, a novel temperature sensing technique, composed of a NOT gates delay line in time domain instead of the conventional voltage domain is proposed to realize a simple architecture without the need for additional on-chip calibrated techniques and laser trimming processes. The time domain circuit was verified successfully by our team. However, the novel circuit still has some problems, for example, higher resolution, lower errors, chip area saving, etc. All performances of the time-domain temperature sensor are optimized firstly, making the sensors ideal for high accuracy, low-power portable applications with VLSI or SOC integration. Two novel structures will be realized in first year. The specifications are 0.1°C in resolution, errors less than ±0.3°C, and 30μW in power consumption. To extend the application of the proposed thermostat, a SAR logic circuit can be directly incorporated with the thermostat to realize smart temperature sensor. The specifications are 0.04°C in resolution, errors less than ±0.3°C, and 5μW in power consumption.[[note]]NSC96-2218-E327-00