ADG1408: What leads to the high noise contribution with this analog multiplexer?

OK, I have a hunch what's going on here. I am looking for simulation results when the switch is closed but I think the initial condition of the circuitry has an open switch. Is there a way to get the noise analysis performed at a certain point in time? How else would I tell the simulation that the switch is closed?

Is no one here who can shed some light on how to perform proper noise simulation at a given condition (switch closed)? Is it impossible in ltspice?

Hello,

We are currently looking into this and will get back to you very soon,

Thanks

David

Hi,

Thanks for your patience.

I like to ask why you are analyzing the noise of the mux_gain output to the digital EN logic, V1 input of the ADG1408?

I have tried simulating the noise of the mux_gain of the amplifier with the ADG1408 connected and disconnected w.r.t. the V9 input and, I don't see any significant difference.

Best regards,
Christian

My apologies for the late reply. The notification from ADI went in my spam folder and since I moved on to the LTC6912, I didn't have the need to monitor this thread.

In any case: does it really matter which voltage source I use as a reference? I have switched from V1 to V9 but see no difference. The noise hovers at around 14 µV/sqrt(Hz) when the mux is used, whereas the reg_mux node shows only about 700 nV/sqrt(Hz).

Hi,

It shouldn't matter whatever voltage source you use as a reference in noise analysis. It seems that the simulation model is not optimized for noise performance simulation.

Best regards,
Christian