I'm struggling to find a proper ground layout for a custom arduino shield I'm designing. It contains 12->5V and 12->10V 5A switching regulators, several H-Bridge motor drivers (rated at a max 1.8A), a TEC driver (rated at max 3-6A ),a pair of octal-switch SPST IC , a pair of shift registers and a DAC among some op-amps, fets and bjts.
I'm following Ott's guide for grounding mixed signal pcbs (http://www.hottconsultants.com/techtips/split-gnd-plane.html). I've got the basics down, but the main issue is that the TEC driver's datasheets implies the existence of a Power Ground on the PCB and considering all the large currents flowing out of the DC regulators, I realize it can be quite relevant. I'm also assuming that the motor drivers would be part of this power ground plane.
My questions: are the digital ICs (Shift registers, SPST switches, digital side of the DAC) really that noise sensitive that a noisy ground would compromise their behaviour? (I suspect only the DAC). If that was not the case, I could just use a single ground for Digital and Power.
I'm considering a power ground (DC regulators, Motor drivers) with two bridges: to digital ground (SRs, Switches) to an analog ground (TEC driver), and additionall a bridge between the digital ground and a second analog ground (with the DAC and analog input pins). Would there be any ground loops with such a configuration?
Also, not so related to this issue but still relevant. To what plane should the GND pins of the Arduino connect? I've read somewhere that they are connected internally, so is it irrelevant?
Any help is welcome!