Pair-single ended to differential signal converter

[Saku]

Hello everyone, I have a project in which I have to transform a pair-single ended signal to a differential one. I know you can use OP and transformers to do that but they give me the following example:



Has anyone any idea how it works? How do you calculate resistors?

Thank you so much for your help.

Regards.

[qdrives]

What voltage levels are we talking about?
What are the output impedances of the two single ended signals?
How accurate must it be (voltage across SD2)?
How fast must it be?

XADC1_N is only driven by C99 compared to AGND over the 845 ohm resistor. So, if XADC1_P is a 'DC' signal, XADC1_N is the same as AGND.

If both XADC1V0 and AIN_0 reference ANGD, then the differential signal is simple these two signals. Do note that most 'differential' signals and actually just a pair of single ended signals as they do not reference each other both a common Gnd (plane).

[Saku]

Hi, thank you for your response. I think SD2 is a protection. XADC1V0 is an output of a microcontroller at 1v. AIN_0 is your analogic input (for example a NTC). The N and P signals are inputs too of the microcontroller. I can't see how this circuits works.

[qdrives]

No, SD2 is drawn like a pair of Schottky diodes.
I also do not see how this circuit works.
Is the differential pair needed for a higher resolution ADC (like on a STM32)? If so, then no it definitely does not work. Use over sampling.

[Saku]

Yes, I think that the case. Thank you so much for your time. I was going crazy trying to figure it out. Like you said, is probably wrong.

[anovickis]

Here's an example on how to do this:

https://www.youtube.com/watch?v=ErVFxBifhIA

I will only add this - if you aren't sure - drop your circuit in p-spice or ltspice, add a stimulus, and plot the output and see what happens.