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ADG714 off resistance

Hi ADI Expert,

I had a project to use ADG714 and needs your support. There is ADG714 schematic as blow: I expected that high resistance Giga ohm between SW1~S4 when sets as opened, Unfortunately the real results not as I expected. The datasheet showed leakage currents 0.1nA at Drain and Source off, thus off resistance equal to Giga ohm.

DMM: BRYMEM BM-817 (3-4/5 Digi 5000 counts, Ohms range: 500K/5000K 0.1% accuracy)

ADG714 supplied voltage that Vdd is 3.3V,Vss is 0V.

Therefore I did more testing as blow:

When ADG714’s SW1~S4 sets to all open and R1 to R4 setup, The resistance few hundreds Kohm between TP1 and TP2.

If closed SW1,which DMM showed 200K ohm between TP1 and TP2.

If only setups R1 200K and R2 300Kohm and removed R3 and R4 in the PCB, then closed SW1, which DMM showed the resistance around 160Kohm, not 200Kohm.

ADG714 off isolation seems not huge Gohm as I expected. 

May I have your suggestion to verify this issue, thanks. 

Best regards. 

Ray.

  • Hi Ray,

    DMMs often have difficulty measuring large resistances accurately. 

    A better way to verify the off impedance of the mux would be put a DC voltage on the source of a closed channel and then measure the voltage that appears on the drain and then use ohms law to calculate the off resistance.

    Regards,

    Stephen

  • It doesn't make sense at all that removing resistors would cause the resistance of what's left to go down since you would have two parallel opens in place of two parallel resistances between. I would have thought you'd see an opposite result, if there is leakage in the switches in the off state.

    I would back up to a simpler condition. Remove all the resistors, check the overall resistance between test points. Clearly, this should be "infinite" since it's an open circuit. If not, then there's something else odd going on in your setup. if that tests as expected, then just try one resistor at a time in your circuit to try each ADG714 path individually and see if those results make sense. if not, then we can focus on one of those simpler scenarios.