【作者】 余国义；

【导师】 邹雪城；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2006， 博士

【摘要】 基准参考源(Reference)是集成电路中一个重要的单元模块,广泛应用于各种模拟集成电路、数模混合信号集成电路和片上系统(SoC)芯片中。随着集成电路产业的发展和半导体制造工艺技术的进步,深亚微米标准CMOS工艺将将成为片上系统(SoC)集成电路设计的主流,因此本论文基于SMIC 0.18μm标准CMOS工艺技术,采用工作在亚阈值区MOSFET设计纯CMOS高精度基准参考源具有一定先进性和代表性。本论文的研究工作主要是包括三个方面的内容,即亚阈值MOSFET基准电路模型的研究、亚阈值MOSFET基准电路的设计和亚阈值MOSFET基准电路的误差修正。对于亚阈值MOSFET基准电路模型的研究。首先基于CMOS器件结构和影响MOSFET阈值电压的因素,分析总结出MOSFET阈值电压的表达式。直接从亚阈值MOSFET漏源电流(即亚阈值电流)的方程中,得到亚阈值MOSFET栅源电压表达式,并分析其温度特性。然后基于SMIC 0.18μm标准CMOS工艺模型,对MOSFET阈值电压和亚阈值MOSFET栅源电压温度特性进行仿真验证,得出设计亚阈值MOSFET基准电路所必需的理论依据。接着基于传统的带隙基准参考源的设计原理,利用工作在亚阈值区的MOSFET的I-V特性,提出了两种亚阈值MOSFET基准电路模型:电压模电路模型和电流模电路模型。对于亚阈值MOSFET基准电路的设计。首先,根据提出的两种亚阈值MOSFET基准电路模型,设计了两款简单适用的低电压低功耗MOSFET基准参考源电路。接着,针对高端消费类电子芯片和通信类电子芯片的性能要求,围绕基准参考源的温度系数和电源抑制比等性能指标,设计了四种低电压低功耗高性能的亚阈值MOSFET基准电路。对设计的每一款低电压低功耗亚阈值MOSFET基准电路均进行了详细的电路原理分析,给出了相关的电路公式和重要的设计参考结论。第一种亚阈值MOSFET电流模基准电路是基于简单的电路配置,充分利用了反馈技术来设计的。其最大的优点是在一定温度范围内具有很低的温漂系数,可以在低于1V电源电压下工作,且功耗也很低,但是其输出基准电压不能任意调节,低频电源抑制比也不是很高。第二种亚阈值MOSFET电流模基准电路是利用不同类型的集成电阻温度系数的差异来设计具有高阶温度曲率补偿的基准参考源。其最大的优点是在比较宽的温度范围内具有较低的温漂系数,但电路中用到了低阻集成电阻,使得芯片的面积较大,而且所需电源电压高于1V。第三种亚阈值MOSFET电流模基准电路是利用nMOSFET和pMOSFET的阈值电压的差异来设计具有高阶温度曲率补偿的基准参考源。由于误差放大器采用了低电压的设计策略,因此这种基准电路可以工作在1 V电源电压下。第四种是一种高电源抑制比的亚阈值MOSFET电流模基准电路。它主要是采用电压调制技术和提高运算放大器电源抑制比的方法,来提高基准参考源的电源抑制比,其低频电源增益可以达到-127 dB。对于亚阈值MOSFET基准电路的误差修正。结合熔丝微调技术和激光微调技术,提出了两种适合深亚微米工艺技术的亚阈值MOSFET基准电路工艺误差的修正方案,并指出其优缺点。接着,逐一分析本论文提出的六款亚阈值MOSFET基准电路的特点,选择合适的方案对输出基准工艺误差进行修正。更多还原

【Abstract】 Reference is an important module in the integrated circuits and widely used in various analog ICs、digital-analog mixed signal ICs and SoC. With the development of IC industry and manufactural technique of semiconductor, deep sub-micron standard digital CMOS process technology will be the main stream of SoC IC design. So it is a certain progress and representative to design a pure CMOS high precision voltage reference circuitry based on the sub-threshold MOSFETs with the SMIC 0.18μm standard CMOS process technique in this thesis.The main contents in this thesis include the following three aspects: the study of reference circuit model based on sub-threshold MOSFETs, the design of reference circuit based on MOSFETs operating in sub-threshold region and the correction of process divagation for reference circuit based on sub-threshold MOSFETs, respectively.Regarding with the study of the reference circuit model based on sub-threshold MOSFETs. Firstly, based on the CMOS device structure and factors affecting the MOSFET threshold voltage, the expression for MOSFET threshold voltage is concluded and then theoretically analyzed. From the quoted equation for the current between source and drain Ids of the sub-threshold MOSFET, the expression for the voltage between gate and source drain Vgs of the sub-threshold MOSFET is directly got and the temperature characteristic of Vgs is theoretically analyzed. The threshold voltage of MOSFET and the voltage between gate and source Vgs of MOSFET operating in sub-threshold region are simulated based on the SMIC 0.18μm standard CMOS process technology, and hence the theoretical foundations for design of the reference circuit based on sub-threshold MOSFET are received. Based on the design principle of traditional bandgap reference and the current-voltage characteristic for MOSFET operating in sub-threshold region, two reference circuit models based on sub-threshold MOSFET are proposed: voltage mode circuit model and current mode circuit model.The design of the sub-threshold MOSFET voltage reference is studied afterwards. Firstly, two simple MOSFET voltage references suitable for low voltage low power are designed which is based on the two models of the sub-threshold MOSFET reference circuit presented. Then, four low power sub-threshold MOSFET voltage reference circuits meeting the development of the senior consuming electronic chips and the communication electronic chips have been designed. While they mainly emphasize on the temperature coefficient and PSRR performance. Detailed deducing of circuit theory、analyzing of working principle are given to every kind of low voltage low power sub-threshold MOSFET voltage reference. Relative theoretical formulas and important design reference conclusions are given.The first kind current mode reference circuit based on sub-threshold MOSFET with the simple circuit arrangement is taken full advantage of the feedback technique to design. Its main virtue is that it has the very low temperature coefficient in a certain temperature range, and can work under 1V supply voltage with low power dissipation .However, the output reference voltage can’t be modulated at will, and the power supply rejection ratio at low-frequency range is not too high.The second kind current mode reference circuit based on sub-threshold MOSFET is high-order curvature-compensated by the temperature coefficient difference of the varying kinds of integrated resistors. Its main virtue is that the reference current with low temperature coefficient in a wider frequency range. However, it is necessary for the circuit to use the low resistivity integrated resistance which will occupy more die area, and the power supply voltage is higher than 1 V.The third kind current mode reference circuit based on sub-threshold MOSFET is high-order curvature-compensated by the threshold voltage difference between the nMOSFET and pMOSFET. It can work under 1 V supply voltage because of the error amplifier designed with the low voltage designing technique.The fourth kind current mode reference circuit based on sub-threshold MOSFET mainly takes full advantage of the voltage regulation technique and the method to increase the PSRR of the operational amplifier to achieve a very high power supply voltage rejection ratio and the circuit’s PSRR is about -127 dB at DC frequency.Finally, the correction of process divagation for reference circuit based sub-threshold MOSFET is presented in this thesis. Based upon the fuse and the laser trimming techniques respectively, two methods to correct the process divagation are presented, which are suitable to trim the reference circuit designed with the deep sub-micron standard CMOS process technology. Moreover, their shortcomings and virtues are given. The characteristics of each circuit presented in this thesis are also analyzed and the suitable trimming method to correct the process divagation is given consequently.更多还原