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ADG1607 - unexpected high crosstalk


I am asking advice on the following issue:

In order to build a multiplexed 4-wire resistance measurement I connected two ADG1607 as seen in the attached figure. A constant current AC signal ( 16 kHz ) is connected to the EXCITE_A and EXCITE_B terminals. I see the expected signal on the selected channel.

What I don't understand is that on all deselected output terminals the signal appears attenuated as well. For example when exciting with a 600 mVrms ( @ 150 micro Amps) sine wave I measure 20 mVrms on all deselected channels which is _much_ more than the expected crosstalk at this frequency according to the specs.

What am I missing ? Is there a general issue in connecting the multiplexers as I did ?

Any advice is appreciated!

Thank you