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AD9245 doesn't work

Rencently,I'm using the converter ad9245,it's a simple chip ,but at the first time ,I find that the outputs of it  are wrong ,the symbol bit does'nt change and the lower 3 bits and bit 12--10 don't change either ,I'm really confuesd .so I begin to check the circute ,to my surprise ,the voltage on the vref pin (pin 24 ) change frequently ,display the voltage on the oscilloscope,the wave like the noise of switching power supply ,almost 140mv.I suspect that my chip is somewhat go wrong ,so I change it ,but the result is the same .After I change the chip ,I quit the internal vref mode ,and choose the external vref mode (the vref  is 1v ) ,the outputs also be the same problem .and I can't understand it ,I 'm looking forward to your help !it's very kind of to answer my qustion!

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