TMUX1101: Aperture jitter estimation

Hello Jose,

From what you are describing you are trying to find out how long the devices input are disconnected from the output. 

In other words you want to know for how long are the switches signal path are truly disconnected electrically. 

You are correct in identifying that this "Jitter/ Uncertainty" will be a fraction of the enable/disable time of both multiplexer, but for these devices we will not be able to find that time.

This because these devices do not have a spec called BBM in their datasheets. Break before make in TI analog multiplexers is the approximate time it takes for the switch to disconnect and actually  connect to the drain pin electrically. 

However if the 74AUC1G66 or TMUX1101 work for you application please continue to use those.

If you would like to find a mux that has Break Before Make speced please checkout this link.

 Please let me know if you need any further assistance!

Hello Kameron,

Thanks for your prompt response. We are using only one switch, so it really doesn't apply the BBM specification.

I will try to explain better. We wonder what is the order of magnitude of the "aperture jitter". I quote the term because it is a specific term in ADCs, sample & hold circuits, and many other timing circuits/building blocks.

Let's suppose I have a discrete sample & hold circuit using one 74AUC1G66 switch. Assuming we call t = 0 the instant in which the control signal transitions from high to low (open to closed), and assuming the control signal clock is jitter free (we have a control signal jitter < 10 ps), what would be the uncertainty in the actual opening of the internal MOS switches with respect to the control signal?

Do you have some insights you can share with us? Is it on the order of tenths of picoseconds? Much larger?

Thank you!

P.S.: As a general rule, in a system, random jitter adds in quadrature (RMS summation), i.e.: resulting jitter^2 = jitter_a^2 + jitter_b^2 + jitter_c^2...

Hello Jose,

Thanks for the clarification and I think I understand your question but please let me know if this doesn't satisfy.

Because you are saying that you want the jitter  when the control signal has already gone from high to low, I interpret that as you want how long it will take for the actual switch path to open or close.

The best information we have for this is called propagation delay and we can calculate to see how long it is with regards to just the switch.

If the switch has no load than the prop delay would be 1RC. At a 5V supply the TMUX1101 has a Ron= 1.8 and Con= 17.( RxC=30.6 Ps)

Please let me know what you think !

Regards,

Kameron

Hello Kameron,

I am well aware of the meaning of the propagation delay and basics calculation around it. My question is about the inherent uncertainty between the control signal and the actual switch opening/closing. You can think of it as if the propagation delay has some statistical variation due thermal noise. As mentioned before, the specification is called "aperture jitter". It is not usually provided in analog switches, that's why I asked for some general indication.

You can have some background here, sorry that I didn't find similar information from TI,

https://www.analog.com/media/en/training-seminars/tutorials/MT-007.pdf

Best regards,

Jose

Hello Jose,

So it actually is hard to say what this aperture jitter would be for a mux and our team doesn't have data to show regarding this.

Multiplexers basically are mosfet switches that turn on gradually and the output voltage on them takes time which is usually dependent on the load of a system.( Which I am sure you know already)

Please let me know if there is any other way I can assist you on this!

Regards,

Kameron