TMUX7412F: parasitic capacitance

Hey Masa,

Masakazu Adachi said:

1. CS and CD are listed in the datasheet, but do you have data on how much they vary depending on the following conditions?

Individual difference, temperature characteristics

Across individual differences (manufacturing variations) I took a look and I wouldn't expect anything more than about +/-2pF. Something to keep in mind though is that we took this data across a handful of devices so it may not necessarily 
We do not have data across temperature. The parasitic capacitance isn't greatly dependent on the temperature, so you shouldn't see much variation here due to temperature.

Masakazu Adachi said:

2. Do you know the parasitic capacitance between S1 and S2 pins?

So we can estimate this using some math and the crosstalk formula. Keep in mind this will be an approximation. 

So using RC = sqrt(A^2/(w^2*(1-A^2)) where A is ratio of Vout/Vin and R is the combination of the series resistor and load resistor (from the test conditions this is 50ohms each) we can get this.

We can solve for A using the known -100dB of cross talk and plugging that into the equation A = 10^(Xtalk/20). 
w(omega) is 2*pi*freq where freq is 1MHz. We can rearrance the RC equation to the following:

We can also rearrange the formula to
C = sqrt(A^2/(R^2*w^2*(1-A^2))

I solve this to be a little under ~0.02pF

Thanks,
Rami 

Hey Masa,

You shouldn't see much variation at all between the all different Sx pins capacitance to GND. Just roughly 1-2pF variation max for on-capacitance and you can expect the variation to be a little tighter for the off-capacitance (closer to 1pF max).

Thanks,
Rami

Hi Rami,

Thanks for the support.

Regards,

Masa