ADG884 switch Bi-Directional..?

Hi

We are using the ADG884 switch in an audio application.

The end device has one mono audio input connector, and the ADG884 is being used to select whether it is in input or output mode - see image below.

Question --- are the audio channels in the ADG884 bi-directional ?  Should running D1->S1A be the same as S1A->D1

In our application we seem to see high noise on the "input mode" path D1->S1A but see low noise on "output mode" S1B->D1

Is it possible the switch is not designed to be driven from D1 and this is causing audio issues..?

Thanks

  • 0
    •  Analog Employees 
    on Jan 21, 2015 2:40 PM

    Hi John,

    The ADG884 source and drain terminals can all be used as both inputs or outputs so yes, the part is bi-directional.

    What kind of noise are you seeing on the signal? Also, what kind of load are you driving in D1->S1A direction?

    Regards,

    Stephen

  • Hi Stephen - thanks for following up.

    The input signal - the noisy one - is an electric guitar - we have a passive circuit after the ADG884. Consequently the input voltages can be quite low amplitude

    The output that's clean is into an electric guitar amp

    The strange thing is when we remove the ADG884 both channels are clean. With the ADG884 the output is fine but the input has a really high noise floor. The signal comes through but there's a lot of noise whether there is a note being played or not.

    Again once we take the ADG out of the input system the noise goes away and the ADG doesn't seem to introduce noise in the other direction

    Any thoughts would be really appreciated

    Thanks

  • 0
    •  Analog Employees 
    on Jan 21, 2015 4:15 PM

    Hi John,

    Have you tried putting the electric guitar signal through the S1B->D1 channel to the passive circuit as an experiment to see if the noise is still there in that direction?

    This could be a useful experiment to see if the noise issue you are seeing is being caused by the direction the mux is being used.

    Regards,

    Stephen