尊敬的Ti公司及各位同行：
我用的是DDC112，通过stm32F1单片机的PWM功能产生两个时钟：第一个是clk时钟，频率12MHz；第二个是CONV积分时间，可调；
第一种情况：DDC112输入端空载，我用PWM输出1000ms的积分时间方波，占空比为50%，那么DDC112工作在continue模式，我用stm32F1的SPI采集结果换算成电流为以下结果：
ch1:-58.96 ch2:-49.04fA
ch1:-37.08 ch2:-46.16fA
ch1:-58.82 ch2:-48.52fA
ch1:-37.04 ch2:-46.68fA
ch1:-58.45 ch2:-48.80fA
ch1:-35.62 ch2:-46.35fA
ch1:-57.84 ch2:-50.07fA
ch1:-33.08 ch2:-44.19fA
ch1:-58.59 ch2:-49.60fA
ch1:-34.64 ch2:-47.39fA
ch1:-58.45 ch2:-50.02fA
ch1:-33.88 ch2:-47.72fA
ch1:-58.73 ch2:-51.15fA
ch1:-33.36 ch2:-45.13fA
ch1:-57.93 ch2:-47.95fA
ch1:-56.94 ch2:-49.13fA
ch1:-35.95 ch2:-46.87fA
ch1:-58.12 ch2:-50.02fA
ch1:-37.60 ch2:-46.45fA
ch1:-59.34 ch2:-49.65fA
ch1:-35.48 ch2:-45.84fA
ch1:-59.34 ch2:-49.79fA
ch1:-35.29 ch2:-48.14fA
可以看出CH1数据有明显的台阶效应，这是为何产生的？
然后我将积分时间设置为50ms方波（占空比50%），同样空载DDC112输入（没接信号），数据如下
ch1:80.00 ch2:-137.41fA
ch1:56.47 ch2:-173.18fA
ch1:-360.47 ch2:-118.59fA
ch1:-340.71 ch2:-82.82fA
ch1:-326.59 ch2:-30.12fA
ch1:-14.12 ch2:-353.88fA
ch1:-31.06 ch2:-370.82fA
ch1:-55.53 ch2:-410.35fA
ch1:-276.71 ch2:25.41fA
ch1:-269.18 ch2:50.82fA
ch1:-275.76 ch2:76.24fA
ch1:-288.00 ch2:22.59fA
ch1:-36.71 ch2:-378.35fA
ch1:-27.29 ch2:-352.00fA
ch1:8.47 ch2:-295.53fA
ch1:8.47 ch2:-266.35fA
ch1:-356.71 ch2:-89.41fA
ch1:-373.65 ch2:-135.53fA
ch1:-375.53 ch2:-174.12fA
ch1:76.24 ch2:-130.82fA
ch1:92.24 ch2:-85.65fA
ch1:97.88 ch2:-71.53fA
ch1:-430.12 ch2:-294.59fA
ch1:-439.53 ch2:-312.47fA
ch1:-447.06 ch2:-327.53fA
ch1:-463.06 ch2:-356.71fA
ch1:137.41 ch2:24.47fA
ch1:149.65 ch2:43.29fA
ch1:139.29 ch2:39.53fA
ch1:-485.65 ch2:-427.29fA
ch1:-488.47 ch2:-429.18fA
ch1:-484.71 ch2:-417.88fA
ch1:-488.47 ch2:-443.29fA
ch1:161.88 ch2:69.65fA
ch1:160.94 ch2:54.59fA
ch1:155.29 ch2:59.29fA
ch1:-488.47 ch2:-407.53fA
ch1:-469.65 ch2:-400.94fA
ch1:-465.88 ch2:-411.29fA
ch1:-467.77 ch2:-385.88fA
ch1:154.35 ch2:45.18fA
ch1:158.12 ch2:49.88fA
ch1:165.65 ch2:25.41fA
ch1:-476.24 ch2:-373.65fA
ch1:-464.00 ch2:-354.82fA
ch1:-468.71 ch2:-354.82fA
ch1:-448.00 ch2:-353.88fA
ch1:144.94 ch2:11.29fA
ch1:134.59 ch2:18.82fA
ch1:130.82 ch2:15.06fA
ch1:-467.77 ch2:-363.29fA
ch1:-458.35 ch2:-368.00fA
ch1:-460.24 ch2:-366.12fA
ch1:136.47 ch2:-1.88fA
ch1:134.59 ch2:8.47fA
ch1:146.82 ch2:26.35fA
ch1:141.18 ch2:39.53fA
ch1:-484.71 ch2:-410.35fA
ch1:-494.12 ch2:-404.71fA
ch1:-495.06 ch2:-415.06fA
ch1:-500.71 ch2:-441.41fA
ch1:170.35 ch2:109.18fA
经过统计分析，能看出周期性波动，波动幅度很大。
请各位帮忙分析一下。
