中文摘要：

AD7745是世界上首款24bit数字输出的电容读取芯片,可以测量一对差分电容。它的输入共模偏置电容最大可到17PF,输入电容变化范围为±4pF,采样频率/通频带为10Hz到90Hz。基于AD7745的微电容加速度计测量电路系统有两种输出方式：一方面通过16bit的D/A将数字信号转换成模拟电压信号,实时输出到示波器;另一方面可将AD7745的24bit输出结果通过串口输入到计算机里,由计算机实现波形显示、分析。对PCB布线进行优化后,试验测得采样频率为90.9Hz时,AD7745数据的实际有效位数为14.5bit,对应分辨率为0.37fF。

英文摘要：

The AD7745 is the first 24bit capacitance-to-digital converter in the world, its capacitance input channel can be configured as single-ended or differential. The AD7745 capacitance input range is ±4 pF, while it can accept up to 17 pF common-mode capacitance with a changeable update rate ： 10 Hz to 90 Hz. There are two different output ways for the AD7745-based micromachined capacitive accelerometer interface circuit： convert the output data to analog signal by a 16bit D/A; or directly put the output data into a personal computer, let the computer handle these data. after the PCB layout optimization, The board has a P-P resolution of 14. 5bit, that is, 0. 37fF.