Sorry, I know repeatly open the same topic is boring.@Gryd3: This is a continuation of numerous posts here and elsewhere by @Chengjun Li in an attempt to understand the internals of the Irvine Sensors MS3110 differential capacitance readout. Why he wants to know this makes about as much sense to me as wanting to know how the internal microcode of a microprocessor executes op-codes. It's certainly of academic interest, but in terms of application usefulness the MS3110 provides all the information you need to use it. Besides that observation, the internal nodes and circuitry of the MS3110 are mostly not accessible, unless you can probe the bare die. You can purchase bare dies for hybrid integration with MEMS devices, but the only easily accessible points are the bonding pads, which are of course available in the packaged product.
The only information I could find on the theory of operation of the MS3110 references a block diagram. As we all know (or should know) block diagrams are simplified explanations of what really goes on in the actual implementation. In this case no timing information is provided, so it's anyone's guess as to how it really accomplishes its "magic" of providing a DC signal proportional to the difference in capacitance presented at the input terminals, CS1IN and CS2IN. Perhaps someone could breadboard the block diagram to see how it works.
The reason I want to know how does MS3110 work is because my advisor asks me to do this. He used to use the MS3110 when he was a student, but with a different transfer function. He said the circuit now shows no difference with the one he used but the transfer function is different, that's why he asks me, one who has no EE background to find out the reason. That's the reason I try to understand the circuit, which is also the reason I am still working on it at nearly 2 am right now. Now I think I can just show him your replies, although I am pretty sure he is not satisfied with this answer.