I am a chemistry student trying to replicate a PCB circuit as part of an extra-curricular challenge. I am in over my head, but I am learning a lot and don't want to give up. I tried to route the design with 2-layers, but I have been unsuccessful in making all the required connections due to density/space issues (board x/y dimensions cannot be increased). Therefore I have decided to try a 4-layered design, based on the assumption that these planes will remove a lot of the tracks/traces that are hindering complete connectivity.
My electro friend recommended the following setup:
Signal/component top layer (jacks,pots,buttons)
PWR internal plane
GND internal plane
Signal/component bottom layer (the layer with all the components).
- A audio-signal processor ( audio delay unit).
- Power consumption: +12V rail: 188mA max / -12V rail: 48mA max
- Digital power : 3.3 V
- Audio output : +10.5V to -10.5V maximum output
- Clock signal output : 0V to 8.2V
- x1 MC - STM32F427ZGT6 - x1 Dram - AS4C16M16SA-7TCN
- x2 CODEC - CS4271-CZZ
- x7 Dual op-amps - https://www.mouser.dk/datasheet/2/294/NJM2068_E-364244.pdf
- x6 Jfet Dual op-amp - https://www.mouser.dk/datasheet/2/389/cd00000492-1795525.pdf
- x1 Non-Isolated DC/DC Converters 3.3V 500MA OUT THRU - 78E-3.3-0.5 https://www.mouser.dk/datasheet/2/468/R_78E_0_5-1711129.pdf
If one is dealing with multiple GND nets ( i.e GND, GNDA, GNDADC) or PWR nets (i.e -12VA, +12V, +3V3, +3.3VADC) and one is not to split PWR or GND planes due to assumed capacitance/inductance/energy level differences, then how does one choose which net is allocated to the respective internal layers?
Tie all the GNDS together in one plane? No - The board contains both digital and analog signals and from what I have read, I assume creating a common ground will result in unwanted noise,ground loops,etc.
Look at the net list, assume that the amount of connections needed for the respective GND/PWR connections should determine which GND/PWR is allocated to the ground/power plane. I.e Look at the netlist, assume that pad count is proportional to required returning GND/PWR connections, highest GND/PWR padcount determines the GND/PWR plane. Alternatively look at the schematic and count the amounts of different GNDs/PWRs in order to decide. This would then be 3.3 V for the power plane and GND for the ground plane.
Any help would be greatly appreaciated.