I am combining both LNA and band-gap reference module. I need suggestion regarding the following.

1>      As there are multiple VDD and GND points, is it a good idea to run parallel slabs of each VDD and GND planes like how its done in digital design?

2>      If we run multiple parallel slabs for each power rails and if we keep individual blocks in between in each of those then some of the MOS device currents become opposite to each other. What are the effects that might occur if we don’t maintain same current directions for all MOS?

3>      It’s always recommended to have a good coupling between VDD and GND. So if I have M1-8 options then which possible combination of metal options I must consider (ex: M1 for GND, M2 for VDD or M7 for GND, M8 for VDD or M1 for GND, M8 for VDD) ?

4>      Regarding 3 by considering maintaining good coupling b/w VDD and GND, I might choose one metal order above or below to one another. If I chose M2 for VDD and M1 for GND then I am unnecessarily providing VDD & GND a highly resistive path but interconnections to modules become easier. Instead if I chose M7 for GND and M8 for VDD, interconnections to lower modules becomes complex but I will be providing lower resistive path for VDD and GND. So which metal I have to choose for these rails and what many factors must be considered?


Thanks and regards,
Vinay Rao.