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I'm attempting to create a sensitive, precise mixed signal system (more than 24bit) compose of a backplane and stacked modules on 2.54mm headers.It is multi-channel and channel's modules are well separated with independent supplies of their own.
The only common module is the DSP, therefore all separate GNDs of all modules will meet at a single point is the DSP's supply GND.

My questions are :

Please take a look and see if there is any problem with my wiring ( quick draft attached below ), both in DC and low-freq noise ( shared impedances in GND return paths ) and HF, spiked noise ( digital and analog return flows ) ?

Is there any advice/caution regarding making a system on backplane ? The 2.54mm hdrs are good enough for 50-100MHz signal ? Any caution making connection through these tiny pins, especially with GND involved ? Should I treat the BCKPLN as a board of wires and traces only, or make use of it's copper planes for some further benefits ?

Thanks.

Here is a quick draft of system wiring :

quick draft of system wiring

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If you trash your sensors, by having PowerSupply trash use the sensor-to-ground path --- ohmic or displacement currents(capacitive) --- then you'll have a 10 bit system.

How bad can this be?

Suppose your SwitchingRegulator has 100pF of capacitance between Line and Output, with 200 volt/200nanosecond edges across that 100pF. The current needing a return path --- and all possible return paths will be explored thru all your sensors --- is

I = C * dV/dT = 100pF * 200v/200nS = 1e-10 * 1e+9 = 0.1 amp

And the driving force is that 200 volts.

Do you wanna bet you can achieve 24 bits, with 0.1 amp exploring all possible stray parasitic paths?

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Suppose one of the sensors is a strain gauge, 200 ohm resistance, glued onto a machine axle with 10pF sensor-shaft/gnd capacitance. What trash-floor can you expect?

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