Low frequency glitches introduced in signal by ADG1606


I am working on a data acquisition system using adg1606 mux and AD7892 ADC. The DAQ works at sampling frequency of 5.12KHz. All the 16 channels of the MUX are used. While giving a sine wave in a single channel a voltage shift in the sine wave when the channel is selected is observed. But this shift doesnot happen every time when the channel is selected. This voltage shift caused by the channel selection happens at a frequency of 320Hz. A sample figure is attached. The MUX gets its input from a switched capacitor filter and a non inverting op amp is given in between the mux and adc. This glitch occurs even if the filter is bypassed. The entire design is implemented on a PCB. In the below figure the current channel is selected at every impulses in the figure. But the voltage shift happens at every 16th selection. This changes if the sampling frequency is increased and goes when reduced to 4KHz. The select signals are clean. 

Thanks in advance

  • Hi Nandu,

    Can you share your application schematic so we can understand how the circuit works?

    Do you have screenshots of the FF:

    • S16
    • D

    Also, can you share a scope shot when filter is bypassed and place the oscilloscope probes at:

    • Channel 1 - AD7892 output
    • Channel 2 - amplifier output
    • Channel 3 - ADG1606 S16
    • Channel 4 - ADG1606 D