Kyle:
I have find the reason for this problem. Because I use five AD9525 in a SPI chain, some of these five chips were now powered. While I powered all these five chips, the phenomenon on SCLK and SDIO disappeared----the amplitude is right and the ring disappeared .
I do not know why no power supply for chips on SPI chain can cause the error on SCLK and SDIO?
Thanks
Regards
Jacky
2014-02-19