Biography
Enrollment Date: 2013
Graduation Date：2016
Degree：M.S.
Defense Date：2016.05.30
Advisors：Liji Wu
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Implementation of Key Module of Batteryless TPMS SoC
Abstract:
High frequency highway traffic accidents makes the tire pressure monitoring system (TPMS) get more and more attention. Currently, TPMS powered by battery dominate the market, the battery life, environmental pollution and installation difficulty become the bottleneck of TPMS development. So, battery-less TPMS have been gathering attention and become the development trend.Battery-less TPMS SoC is the research topic of our team, and a two-step schema is adopted: the first step is to complete the design of TPMS SoC which is powered by battery; the second step is to achieve the battery-less TPMS SoC.Firstly, this paper completes the design of pressure sensor interface circuits, which includes instrumental amplifier (IA) and 8-bit low-power SAR (Successive Approximation Register) ADC. Three op-amp structure IA is adopted which reduces power consumption by up to sixty percent compared with the previous version. To reduce power consumption, an 8-bit low-power SAR (Successive Approximation Register) ADC, with a modified switching method, is designed. The proposed design reduces the average power consumption in the DAC by 87.5％during digitization. Post simulation results show that at the power supply of 3V and reference voltage of 1.5V and with the sampling rate of 2kS/s, the average dynamic power is 0.9uW, and the ADC can digitize the input signal in a full-scale range of 3V with ENOB of 7.6bits and SNDR of 63.2dB.It can work steadily with a temperature range of -40~125℃. The ADC can meet the requirement of Battery-less TPMS.Secondly, this paper analyzes the power requirement of each module of the TPMS SoC. Due to the battery-less TPMS provides power for the chip in inductively coupled manner, which limits the transmitted power of the coil, each module of the SoC needs to reduce power consumption as far as possible. To reduce the power consumption of the 8051 MCU used in TPMS SoC which is powered by battery, this paper completes the design and FPGA verification of a new MCU. The MCU is designed based on 40 instructions of the instruction set of 8051 MCU. Instruction pre-fetch unit is designed according to the 8051 instructions to speed up the instruction execution. According to the requirements of international standard ISO26262 and working characteristics of the TPMS, low power and reliability design are considered. Logic synthesis results show that the area decreases 2/3 and the power consumption decreases 3/4. The MCU can meet the requirement of battery-less TPMS.Finally, this paper completes some other key modules design of second edition of TPMS SoC. Power on reset and brown-out reset circuits of MCU, output buffer of power management and startup circuit of error amplifier of bandgap are designed and added to the SoC. The layout has been completed and taped out.