Hi Ven,
Thank you for your question. The AFE is looking for an analog input to the device. I am not an expert on the AFE4400, but I believe that you would want to use a balun to convert a single-ended to differential signal. Mini Circuits has several options to choose from, depending on your input frequency: RF Transformers and Baluns (minicircuits.com)
The main thing to consider here is the input full-scale range of the device. Because the TIA has a full-scale range of ±1 V, TI recommends that the input to the ADC does not exceed ±1 V, which is approximately 80% of its full-scale (datasheet pg. 74)
I have also drawn you a diagram for this situation. It is helpful to understand this diagram along with the diagram in the AFE4400 datasheet on pg. 72. Notice that the AFE4400 datasheet mentions a Vcm = 0.9 V (datasheet pg. 9, “Common-mode voltage on input pins”). This means that the differential signal IN+ / IN- will swing around 0.9V. I understand the ±1 V to be a maximum swing of 2 Vpp, so each differential leg has an allowable swing of 1 Vpp. Here is another helpful reference to understand this: (+) [FAQ] ADS5263: Differential input voltage swing vs single-ended signal pk-pk voltage.
I also found this to be a helpful resource (question 11): (+) AFE4400 / AFE4490 / AFE4403 / AFE4404 FAQs
Regards, Amy
