想问一下McNeil的文章“Jitter in Ring Oscillators”的一个问题

红红的西瓜

为什么(a)和(c)是闭环，而(b)是开环呢？

icdane

(c) is measuring the osc itself, while the other two are in a CDR like loop.

红红的西瓜

   

icdane 发表于 2023-5-9 10:13
(c) is measuring the osc itself, while the other two are in a CDR like loop.

谢谢回复。文章说(c)中CDRPLL是开环的，那么PLL中的VCO输入是通过什么方法固定住控制电压吗？（设置固定的控制电压来断开PLL正常工作时的环路）
另外，请问一下(a)和(e)分别用TCLK和RCLK去触发仪器，得到的统计结果tao会有什么区别呢？

icdane

the details are on page 3 in the paper.
for (c), the oscillator is free running, meaning no one is controlling it. the output of the osc is used as both the trigger and input of the oscilloscope (with internal delay between these two so one can sample the other).
I do not quite get your second question. but (a) seems only shows the histogram result and you can derive the variation from it; (e) provide more instrument that you can see the variation relationship to the loop bandwidth (which can be used in design implementation?)