一种电流注入补偿的电容测量电路  

A capacitance measurement circuit with current injection compensation

作　　者：杨柳 段威 李逸凡 任仟 宋敏 YANG Liu;DUAN Wei;LI Yifan;REN Qian;SONG Min(Hubei Key Laboratory of Ferro-&Piezo-electric Materials and Devices,Physics and Electronic Science collage,Hubei University,Wuhan 430062,Hubei,China)

机构地区：[1]湖北大学物理与电子科学学院铁电压电材料与器件湖北省重点实验室,湖北武汉430062

出　　处：《微电子学与计算机》2021年第10期91-96,共6页Microelectronics & Computer

基　　金：国家自然科学基金项目(61904051)。

摘　　要：电容式触摸屏测量系统主要实现电容到数字信号的转换,但芯片IO及PCB板上存在的寄生电容会严重影响电容测量电路中微小感应电容的测量精度.针对该问题,提出了一种基于电流注入的补偿时间可调的电容测量电路.详细分析了电路中存在的失配误差,进一步改善了电容测量的精度,适当改变电路中相关量的参数值,可有效提高电容测量的动态范围.基于SMIC 0.18μm标准CMOS工艺进行电路设计,整体版图面积约为0.21 mm 2.采用Spectre工具对电路进行仿真,结果表明:该电容测量电路在-40℃~125℃范围内,测量0~1 pF的感应电容,转换时间约为50μs,分辨率可达到1 fF,转换得到12位数字信号的信噪比为70.1 dB,有效位数为11.56 bit,电源电压为1.8 V,总功耗为0.19 mW.The capacitive touch screen measurement system mainly realizes the conversion of capacitance to digital signal,but the parasitic capacitance existing on the chip IO and PCB board will seriously affect the measurement accuracy of the small inductive capacitance in the capacitance measurement circuit.To solve this problem,a capacitance measurement circuit with adjustable compensation time based on current injection is proposed.The mismatch error in the circuit is analyzed in detail,and the measurement accuracy of capacitance is further improved.The dynamic range of capacitance measurement can be effectively improved by appropriately changing the parameter value of the relevant quantity in the circuit.The circuit design is based on the SMIC 0.18μm standard CMOS process,and the overall layout area is about 0.21 mm 2.The circuit is simulated using Spectre tool,and the results show that the capacitance measurement circuit inductive capacitance of 0~1 pF in the temperature range of-40℃to 125℃,the conversion time is about 50μs,and the resolution can reach 1 fF,the signal to noise ratio of the converted 12 bit digital signal is 70.1 dB,the effective number of bits is 11.56 bits,the power supply voltage is 1.8 V,and the total power consumption is 0.19 mW.

关 键 词：电容式触摸屏 寄生电容 感应电容 电流注入补偿 

分 类 号：TN432[电子电信—微电子学与固体电子学]