| ??? 07/23/09 20:10 Read: times |
#167773 - Explanation Responding to: ???'s previous message |
Hi Joe,
Joseph Hebert said:
[...] the impedance (the capacitance in particular) of the ground plane relative to the signal trace. Ehm, surely you mean the inductance? If a trace passes over a discontinuity in the plane, it experiences an abrupt increase in impedance and becomes a slotted antenna. Exactly! Any signal crossing the analog/digital boundary must therefore be routed over the area where the analog and digital planes are connected. For some excellent advise on split planes see this page: http://www.hottconsultants.com/techtips/...plane.html Now please explain to me what difference it makes which is on top. For an all conventional board: None. But for an SMT board, you cannot help but allow many, many discontinuities in the plane! Plus the fact that this means you'd have to route each and every signal to a different layer, which is awkward from a draughtsman's point of view. It also means via's abound. While this is no longer a very big problem in terms of manufacturing, you must remember a via also represents an impedance discontinuity and thus a (potential) source of EMI. Also, I would definitely not like to rework a board where all the signal traces are 'buried'! Rob. |
| Topic | Author | Date |
| PCB design - ground plate... | 01/01/70 00:00 | |
| excuse... | 01/01/70 00:00 | |
| You can use a local ground plane, but... | 01/01/70 00:00 | |
| So, if I understand it well... | 01/01/70 00:00 | |
| Yes, of course, but... | 01/01/70 00:00 | |
| Yes, but... | 01/01/70 00:00 | |
| No overlap | 01/01/70 00:00 | |
| Version B, but without FB... | 01/01/70 00:00 | |
| so... | 01/01/70 00:00 | |
| PCB layout... | 01/01/70 00:00 | |
| Answers... | 01/01/70 00:00 | |
| EMC | 01/01/70 00:00 | |
| Hhm, I wouldn't do that... | 01/01/70 00:00 | |
| AC power supply | 01/01/70 00:00 | |
| ground vias | 01/01/70 00:00 | |
| Locating of vias... | 01/01/70 00:00 | |
| Thank you very much... | 01/01/70 00:00 | |
| Sideplating? Thermal vias? | 01/01/70 00:00 | |
| Stackup | 01/01/70 00:00 | |
| Not such a good idea | 01/01/70 00:00 | |
| interrupted/split planes | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| Thank you... | 01/01/70 00:00 | |
| Nice link, Rob! | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| Explanation | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| What you propose isn't well suited for 4 layer boards | 01/01/70 00:00 | |
Hi Kai | 01/01/70 00:00 |