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TMUX1072: What is the correct ON capacitance

Josef Alt
Intellectual 1605 points
Part Number: TMUX1072

My customer is performing a LTspice simulation of TMUX1072 and used R=18ohm and Con=6.2pF but wonders 6.2pF is the correct value to use:

They are a bit confused about this specifications because the dynamic characteristics would imply that the COM side and the NC,NO side would both have a capacitance of 6.2 pF max.

So we would expect that if the switch is closed the total capacitance is 12.4 pF max but this capacitance is also specified as 6.2 pF.

Could you clarify what the correct channel ON capacitance is?

Thanks

Josef

  • 0
    TI__Expert 5660 points

    Hi Josef,

    The ON capacitance is the capacitance of the switch when the switch is ON. When the switch is ON, it can be thought of as a low impedance short circuit "wire" (with small resistance and capacitance characteristics). Because of this, the ON capacitance looking from either COM side port or NC,NO side port will be the same, as indicated by the spec (6.2 pF max) - there's no need to "add" the capacitances together, this spec is referring to the same capacitance.

    Regards,
    Kate