應用於可植入式神經感測微系統之低功率無線資料傳輸

Abstract

本論文研製之無線資料傳輸電路主要目的在設計與實現一個低功耗、低面積、低溫度與製成飄移對VCO敏感度、寬輸出擺幅之無線資料傳輸晶片。資料經晶片內部OOK調變後，電感耦合到晶片外面接收端interposer，然後再經外部OOK解調電路來解調回來。本論文僅使用開迴路電路解決震盪頻率受到製程而漂移很大的問題，晶片內完全只用到MOS元件，沒用到任何一個被動元件，而不是像一般使用特別的鎖相迴路解決此問題，因此可省下不少功率跟面積。本論文採用CMOS帶差參考電路操作在次臨界區來消除MOS臨界電壓以降低製程飄移對振盪頻率的改變，此方法不須額外的補償或是校正電路，如此可省那些電路所耗的面積跟功率，並且電路操作在次臨界區也可降低偏壓電路的功率與操作電壓。本論文所用的參考電壓源的壓控振盪器提供穩定的電流以使壓控振盪器的震盪頻率可變動不大而可對抗製程飄移跟溫度變化，且電路為低功耗、低面積、寬輸出擺幅設計，並且本論文所用的參考電流源的壓控振盪器比所用的參考電壓源的壓控振盪器還多了可抗電源雜訊之優點，他使用增益提升(gain-boost)電路跟汲取電流式(Current-starved)環形震盪器方法來雙重抵抗電源雜訊。本論文的無線傳輸晶片裡面的壓控振盪器與OOK調變器均採用差動輸入差動輸出，可降低輸入訊號雜訊，以及增加輸出擺幅。本論文透過國家晶片系統設計中心使用TSMC 180nm CMOS 製程來製作晶片。模擬的結果顯示所用參考電壓源的晶片功率消耗382μW，晶片佈局總面積為0.027mm2，其壓控振盪器的振盪頻率為256 MHz，在攝氏0~50度溫度造成的壓控振盪器振盪頻率變化為4.3%，由製程飄移引起的壓控振盪器的振盪頻率變化為29%；所用參考電流源的晶片功率消耗354μW，晶片佈局總面積為0.036mm2，其壓控振盪器的振盪頻率為400 MHz，在攝氏0~50度溫度造成的壓控振盪器的振盪頻率變化為4.2%，由製程飄移引起的壓控振盪器振盪頻率的變化為27%，在正負10%供應電壓造成的壓控振盪器的振盪頻率變化為3.3%。

This thesis, aims to design and implement a low power-consumption, less area, low process variation and temperature sensitivity to voltage controlled oscillator (VCO) and wide swing of output on wireless data transmission chip. The wireless data transmission system receives wireless data by the data which passes the OOK modulator, then it passes the inductive coupling via an on-interposer of receive terminal inductor which is out of the chip. Then it passes the OOK demodulator to recover the data. In this thesis, only the open-loop circuit is used to solve the problem that the oscillation frequency is drifted a lot by the process variation. The chip is used only all-MOS element, and we do not use any passive component on chip, rather than the general use of the special phase-locked loop to solve the problem, thus it can save a lot of power and area. In this thesis, the CMOS bandgap reference circuit is used to eliminate the MOS threshold voltage in the subthreshold region to reduce the VCO oscillation frequency deviation caused by the process variation. This method requires no additional compensation or calibration circuits. Hence it can reduce the area and the power of those circuits. Circuits operate in the subthreshold region can also reduce the power and operating voltage of the bias circuits. In this thesis, the purposed VCO with voltage reference provides stable current to oscillate at a fixed frequency against process and temperature variations, and the circuit is low power consumption, low area, and wide output swing design, and the purposed VCO with current reference is also less susceptible to against supply noise variation than the purposed VCO with voltage reference. We use the current-starved method and gain-boost method to against supply noise variation. In this thesis , the VCO and OOK modulator of wireless transmission chip are used differential input and differential output which can reduce the input signal noise, and increase the output swing. This thesis through the National Chip Implementation Center to tape out the chip with TSMC 180nm CMOS process. The simulation results show that the chip power consumption of the purposed wireless data transmission system with the purposed voltage reference is 382μW.The total area of the chip is 0.027 mm2.The oscillation frequency of the VCO is 256MHz.The variation of the VCO oscillation frequency is 4.3% at 0~50℃. The variation of the VCO oscillation frequency caused by the process variation is 29%. The chip power consumption of the purposed wireless data transmission system with the purposed current reference is 354μW.The total area of the chip is 0.036 mm2.The oscillation frequency of the VCO is 400MHz. The variation of the VCO oscillation frequency is 4.2% at 0~50℃. The variation of the VCO oscillation frequency caused by the process variation is 27%. The variation of the VCO oscillation frequency caused by the supply variation at plus or minus 10% supply variation is 3.3%.