TMUX4052: TMUX4052 application on ADC sampling

Hello Shaohui,

1. What 120ohm are you referring to? I am assuming you are looking at the VDD = 24V case.
    The Ron goes from mux of 120ohms at 25C to 150ohms at 85C.

Also, what measurements did you get? Also I think you measured at 18V supply instead of 24V. You will get different Ron values with a different supply level.

2. You can measure Ron as the following:

Use -1mA for ISD and sweep VS from 0V to 18V. VDD should be 18V too.

3. We usually see ADC sampling with our TMUX1308A. We also have an app note on showing how it affects the signal in ADC sampling application. 

Thanks,

Nir 

Hello Nir,

Thanks for your respond! The 120ohm comes from the below table which is its datasheet. 

We are more concerned about the temperature drift of the Ron resistance. The draft schematic is below. It will impact the ADC sampling of R4 (from 920 ohm to 1.5Kohm) if chip's Ron temperature drift is too bigger. 

As if 3.3V drain voltage is not within the stable range of Ron which shows as below picture. Is this correct? What is your opinion on this? Is it better to use positive and negative voltages?

For TMUX1308XX, under different power VDD voltage, its Ron resistance is not stable compared to the TMUX4502. For the Analog multiplexing, they are all typical applications. Based on our application, what are the differences between them?

Thanks 

Shaohui Wu

Hello Shaohui, 

I see thank you for clarifying, but those are max specs. They are there to provide additional head room. I believe in practice the Ron difference will be much less. 

For Ron drift across temp I recommend looking at the actual graphs at section 6.8. It will show you how the Ron dirft will look like with more details. 

Its not about "stabilization" here. The mux internally is an NFET and PFET. So when you are close to 0V or to  VDD you will see higher Ron since one of them turns off. This is why you see the peaks on the edges of the curves. 

Supply voltage doesn't really matter where it comes to Ron drift. It will be very similar in any supply option. 

TMUX1308 is just most commonly used for ADC sampling due to its configuration. Ron drift is not a major concern when customers use it.

Since Ron drift is very critical here, will a device such as the TMUX4821 work for you? The Ron drift is very small, but the configuration is either a 2-channel 1:1 or 1-channel 2:1.

Thanks,

Nir 

Hello Nir,

Thank you for your reply. There is still one question that I need to confirm with you, which is the figure 6-3 shown above. The draft schematic's operation conditions are below.

1.A channel source and drain voltages are both close to 3.3V, the VDD is 18V 

2. Vss and GND are 0V 

My concern is its Ron operating on the highlight by red range that is no preferred for application due to it is no "stabilization". Not at all suitable for calibration purposes

Please correct me if my understanding is not right. That is why ask whether it is better if operation with positive and negative voltages.

Thanks

Shaohui Wu