Other Parts Discussed in Thread: REF3425, REF6225
Dear Ahmed,
First of all, thanks for your work on this reference design and for answering questions on this forum. It's difficult to overestimate you help.
I have some more questions related to this reference design.
1. The first question is a bit amateurish, but still: Why do we need several attenuation ratios? Most of IEPE sensors have output range equals 10 V (+ -5 V). In this case, we only need 1/16 settings for matching with amplifiers of the amplification stage. Why we need another settings (1/2, 1/4, 1/8)? Should we use them only with sensors, whose output range respectively 1.25V, 2.5V, 5V? Or is there another explanation?
2. The second questions about multiplexing inputs. As you said earlier, the best option is to position the multiplexer after the HPF stage. What about common-mode supply? Should it be after multiplexer, one item for whole scheme? Or we need several common-mode supplies before multiplexer?
3. The third question about coupling capacitor (C35) at HPF stage. In this reference design you have used ceramic capacitor (1 μF, 50 V, +/- 10%, X7R, 0603). Is it sufficient for production use? Or the special audio capacitor can be used? I saw Metallized Polyester Capacitors (PET) in ADC's equipment for IEPE sensors like WIMA MKS 4. In other words, is the capacitor an important element of the circuit that makes sense to improve?
Best wishes,
Victor