【作者】 汪进；

【导师】 许磊；

【作者基本信息】 中国科学技术大学 ， 电子科学与技术， 2020， 硕士

【摘要】 随着科技的发展,人们对环境问题日益关注,气体传感器已经应用到日常生活中的诸多方面。MEMS气体传感器通过表面敏感材料电阻的变化来反映空气中目标气体的浓度,需要设计专门的后端检测电路将该变化值实时显示在电脑上。完整的后端检测电路需要包括参数测量、信号转换以及实时传输的功能。同时为了拓宽气体传感器的应用范围,该电路必须要有控制功能,支持多种工作模式。但是目前后端电路多关注于测量电路,控制接口电路并未详细设计,需依赖于各种仪器设备方可正常工作。因此本文将基于两种常用的测量电路,从芯片功能的完整性出发,设计两款控制接口电路芯片,能够实现后端检测电路所需的所有功能,以保证系统的便携性与灵活性。首先本文基于传统的电阻分压法设计了一款控制接口电路芯片。该芯片为数模混合芯片,模拟部分利用电阻分压电路以及ADC电路将电阻信号转变为lObit的数字信号,数字部分主时钟频率为8MHz,利用对特定寄存器进行配置实现了对系统的灵活控制,提供了多种工作模式,利用I2C接口完成了与外界的数据交换,满足了后端检测电路的所有需求。本芯片在SMIC180nm CMOS工艺下完成流片,数字部分尺寸为0.32mm×0.16mm。测试结果表明,本芯片在3.3V工作电压下可以完成100Ω～100kΩ范围内的电阻测量,电阻分压电路测量误差小于2%,整体测量误差小于5%。其后为了增大测量范围、提高测量精度以及增强系统的通用性,本文在前款芯片基础上设计了一款基于RTF电路的控制接口电路芯片。该芯片模拟部分利用RTF电路将电阻转换为电压方波信号,数字部分主时钟为8MHz,完成了对电压方波信号的频率测量、对系统的控制以及通信功能,还提供了 6种不同的工作模式,包括低功耗的脉冲加热模式以及定时唤起模式,集成了 I2C接口、UART接口以及PWM输出等多种通信接口。利用FPGA对数字部分进行验证可知,本芯片数字部分可以完成l0Hz～2MHz范围内信号的测量,10Hz～1kHz范围内信号测量误差不高于2%,lkHz～2MHz范围内信号测量误差不高于1%。本芯片在SMIC180nm CMOS工艺下完成流片,数字部分尺寸为0.56mm×0.28mm,测量范围以及测量精度均有大幅度提高,能够更好的满足后端电路需求。流片成功后,结合芯片与气体传感器进行联调测试。在仅提供工作电压的情况下系统即可正常工作,能将测试结果传输至上位机实时显示,通信速率可达400kbps。使用该系统对乙醇气体、乙二醇气体、氨气以及氢气进行测试,最小分辨率为0.1ppm,最大响应度可达8.3。同时将该系统应用到食物新鲜度检测领域,可以很好的完成采集以及识别功能,解决了现有系统功能不完整、工作不独立的问题,具有较好的实用性、便携性以及创新性。更多还原

【Abstract】 With the development of technology,people pay more and more attention to environmental issues,and gas sensors have been applied to many aspects of daily life.The MEMS gas sensor reflects the concentration of the target gas in the air through the change in the resistance of the surface-sensitive material.Therefore,it is necessary to design a special back-end circuit to display the resistance change value on the computer in real time.The functions of complete gas detection system needs include measurement,signal conversion and real-time transmission.Moreover,in order to widen the application range of the gas sensor,the back-end circuit must have a control function and support multiple working modes.However the current back-end circuits on the market only focus on the front-end detection,the subsequent control interface circuit is not designed in detail.The current circuit cannot realize the complete system control communication function which needs to rely on various instruments.Therefore,this thesis will design two control interface circuit chips with complete functions based on two commonly used measurement methods,which can implement all the functions required by the back-end detection circuit to ensure the portability of the systemFirst of all,this thesis designs a control interface circuit chip which based on the resistance voltage division method.The chip is a digital-analog hybrid chip,which analog part uses a resistance divider circuit and an ADC circuit to convert the resistance signal into a 10-bit digital signal.The main clock frequency of the digital part is 8MHz,which realizes flexible control of the system by configuring specific registers,provides a variety of work mode and completes the data exchange with the outside world by the I2C interface.The chip meet all the requirements of the back-end detection circuit.The chip is taped out in the SMIC 180nm CMOS process,and the digital area is about 0.32mm×0.16mm.The experimental results show that the chip can complete the resistance measurement during the range of 100Ω～100kΩ under the working voltage of 3.3 V.The measurement error of the resistance divider circuit is less than 2%,and the overall measurement error is less than 5%.Later,in order to increase the measurement range,improve the measurement accuracy and enhance the versatility of the system,this thesis designs another control interface circuit chip using RFT method based on the previous chip.The analog part of the chip uses RTF circuit to convert the resistance into a voltage square wave signal.The main clock of the digital part is 8MHz,which completes the frequency measurement of the voltage signal,the real-time control of the system,and the external data exchange function.It also provides 6 different working modes,including low-power pulse heating mode and timing wake-up mode.The data exchange module includes various communication interfaces such as I2C interface,DART interface,and PWM output.The verification of the digital part by using FPGA shows that the part can complete the measurement of signals during the range of 10Hz～2MHz.The signal measurement error during the range of 10Hz～1kHz is not higher than 2%,and the signal measurement error during the range of 1 kHz～2MHz is not higher than 1%.This chip is taped out in SMIC 180nm CMOS process,and the digital area is 0.56mm×0.28mm.The range and accuracy of measurement have been greatly improved,and it has good application value,which can better meet the needs of back-end circuits.Combining the chip with the gas sensor for testing,it can transmit the test results to the computer for real-time display that the communication rate can reach 400Kbit/s,which only needs to provide the working voltage.The system is used to test alcohol,ethylene glycol ammonia and hydrogen with a minimum resolution of 0.1 ppm and a maximum response of 8.3.In addition,the system is applied to the field of food freshness detection,which can complete the collection and recognition functions very well.The system which has good practicability,portability and innovation solves the problems of incomplete functions and independent work of the existing design.更多还原