I am using the AD9650.
In my board, the noise appears in the VIN± pin of the AD9650 when the analog to digital conversion starts.
The amplitude of the noise is about 200mVp-p.
The noise is a square wave, and the same cycle as the sampling clock of the ADC.
I tested change the ratio of dividing frequency of the sampling clock.
Then, the cycle of the noise changed similarly, too.
I removed the circuit connected with VIN± pin.
I measured the VIN± pin in the state.
The noise appeared though the VIN± pin was non connection.
I think that the circuit connected with the AIN± pin is not a cause.
I want to find the cause that the sampling clock does leaks to the AIN± pin.
Please give me some advice about the cause.