Hi to all from the RSA !
Does using layers on pcbs create a capacitive condition ?
If one layer is positive power supply and another layer is negative power supply, should they be on the same side or on opposite sides of the pcb?
Will they interact with ground plane layers ?
Thanks in advance for your comments !!
Does using layers on pcbs create a capacitive condition ?
If one layer is positive power supply and another layer is negative power supply, should they be on the same side or on opposite sides of the pcb?
Will they interact with ground plane layers ?
Thanks in advance for your comments !!
Yes, all these can interact from their capacitance. High speed boards have a complete layer for each DC voltage and ground.
Not an expert on PCB stackup, but I believe this is something that depends a bit on what your circuit is and which frequencies etc. are involved. A few discussions that I know of:
https://resources.pcb.cadence.com/blog/best-formats-for-4-layer-pcb-stackups
https://www.allpcb.com/4_layer_pcb.html
Etc.
https://resources.pcb.cadence.com/blog/best-formats-for-4-layer-pcb-stackups
https://www.allpcb.com/4_layer_pcb.html
Etc.
Hi Garry, it does not matter. You normally try to keep tracks as short as possible and avoid them being parallel, ie cross the tracks where signals may interfere (on different layers). don't care how many vias you use. And yes all tracks capacitively couple with each other somewhat. If you have a "ground plane" try to get the ground in between tracks wherever you can, i.e. with the ground pour function. It is like building a little barrier between tracks. What program are you using?
Thanks for your responses, and especially for the web resources !!
Tha application is opamp based circuitry where the power supplies will be as full planes - ie: one as pos. supply and the other as neg.
If the two planes are on opposite sides of the board, they surely must create a capacitance, and if they are the outer layers then it seems that the circuitry - the inner layers - will be operating as if within a discreet capacitor . . . .? !!
Tha application is opamp based circuitry where the power supplies will be as full planes - ie: one as pos. supply and the other as neg.
If the two planes are on opposite sides of the board, they surely must create a capacitance, and if they are the outer layers then it seems that the circuitry - the inner layers - will be operating as if within a discreet capacitor . . . .? !!
Hi Nico, yes, I have arranged for the ground planes in between tracks. Am also considering additional dedicated planes for signal grounding as well as power grounds too.
Using Sprint EDA for the pcb, it's a bit tedious but by using two (or more) instances of the prgm and copying from one to the other, it is possible to get 8 or more layers on the pcb.
Using Sprint EDA for the pcb, it's a bit tedious but by using two (or more) instances of the prgm and copying from one to the other, it is possible to get 8 or more layers on the pcb.
At audio frequencies I'd just use ground planes, wire the supplies without planes so they don't couple to everything as they carry non-linear currents and voltages, whereas the ground normally only sees the linear return currents from the load(s). Understand about the non-linear currents injected from decoupling caps and place the +ve/-ve decoupling caps close to each other and with a common trace to the ground plane.
At audio frequencies in low impedance circuits the capacitive coupling isn't a major issue like it is at higher frequencies, but if you are aiming for ppm levels of distortion it doesn't take much signal injection from the wrong source to dominate the distortion performance.
At audio frequencies in low impedance circuits the capacitive coupling isn't a major issue like it is at higher frequencies, but if you are aiming for ppm levels of distortion it doesn't take much signal injection from the wrong source to dominate the distortion performance.