已回答假定已回答

AD9901输出不稳定

yuning 在 2014-9-4 詢問的問題
最後回覆由yuning於2014-9-11提供

您好!我在使用AD9901作为PLL的鉴相器实验。搭好了电路后,我将两路加了偏置的方波接到两个输入端,输出是一个脉冲,如datasheet一样。但当我改变其中一个方波的相位时,刚开始时输出也随着变,但突然输出跳到3.2V,而且一直保持在3.2V,直到我把相位往回调,在某个瞬间,输出突然变回正常的脉冲。有时会跳到5.0V,以上的现象出现很随机。不知道是什么原因?请指教。

谢谢!

Hello, I am planing to build an all digital PLL using AD9901 as a phase detector. As far as I am informed, AD9901 has an internal phase/frequency detector to compute the error signal. When two square waves with the same frequency are applied to the two input (REF_IN and VCO_IN),the output swing is approximately +3.2V to +5.0V ,it really did a good job so far.However,question comes up when I change phase difference of the two inputs,the output suddenly became +3.2V dc,or sometimes became +5.0V dc, and sometimes it came back to right swint +3.2V to +5.0V.How strange it was since the inputs are right all along,the only diffrerence is the phase,but the output is unstable.

Another condition is,two inputs remain unchanged , when I touch the REF_IN or VCO_IN with a metal bar,the output will change between the 3 states mentioned before.

Does it mean that the output is unstable or it is sentitive to be affected by the other factors. maybe there are some more hints I should take into account. Thank you. The following figure is my schematic diagram.

Best,

yuning

結果