I have a precision application where I am demodulating two sine waves using an analog mux (ADG613) and then Low pass filter to measure it's amplitude. The ADG613 is a 1:4 MUX made into a DPDT (chosen because of its low charge injection) by connecting S2 and S1 together and S3 and S4. Then the inputs are D1 & D2 and D3 & D4
I think that in between break before make, where the output is connected to nothing I get some 'leakage spikes'
here is the SPICE simulation. I can't exactly see where the spike is in the simulation but a clue is the current going into the MUX.
I am wondering if I can put a pull down resistor on the output of the Demodulated signals (input of LPFs) to prevent these types of spikes/glitches but not lose precision or signal integrity on the output of the LPF. above are pictures of using a 300 ohm pull down on the de-modulated signal output. I think the glitches are happening during that break before make period where only leakage currents are rushing to the output.
If using a pullup resistor I will be wasting some power, maybe there is a better way to clamp down that make before break error?
The MUX inputs have some Ron resistance about 85 ohms to 115 ohms, a max of 40 ohm flatness, and a max of 4 ohm matching. The error between Demodulated output and inputs is not going to be precise because of that voltage drop. Should that be anything to worry about on the output of the LPF?
Thanks in advance