Ground pour in audio circuit with SMD components - Page 1
Forum section: electronics / projects

author: firstcolle
author_rank: Regular Contributor
timestamp: January 22, 2018, 08:19:31 am
content: Hi,I'm working on a 2 layers PCB for an audio application and I use all SMD parts.In this case, how is the best solution for place the GND pour and traces?I did the first layout with GND pour and signal traces on the top layer and power line on the bottom layer. In this case the GND is connected directly to the pins of the components but is also interrupted many times by traces and components.Is better to put it on the bottom layer and place a via for every GND pin? Or is better to keep it on the top layer and route the signal traces on the bottom layer?many thanks!

author: Sjoertdb
author_rank: Contributor
timestamp: January 22, 2018, 08:30:05 am
content: I've done an audio layout too in my last project, but in order to keep the ground loop as low as possible, it's best to connect all the audio components in ground groups. At last connect them via a single ground trace to the main ground. Also, try to keep the distance between the grounds.My suggestion: On the bottom layer, a single and seperated pour for the audio analog ground. Distance (1mm?) inbetween the analog ground and the digital ground.-Seperate analog & digital supply using ferrite bead in the supply rails-Single ground connection between digital & analogI've included how I've done this (still needs to be tested, waiting for boards):

author: AndyC_772
author_rank: Super Contributor
timestamp: January 22, 2018, 08:42:27 am
content: Think carefully before separating grounds; there's a lot to be said for having a single, unbroken ground plane, and joining everything straight to it.Popular "wisdom" might be to chop up the ground into lots of little bits, but it's not necessary or even beneficial in many cases. This is especially true if you need to pass EMC.Think about power as well as ground; current flows in loops, and you need to consider the impedance of the power net just as much as the ground plane. With a 2 layer board you don't have enough layers to do this properly.The best solution to your layout problem is to use a 4 layer board. Sticking with 2 is inevitably a compromise.

author: firstcolle
author_rank: Regular Contributor
timestamp: January 22, 2018, 12:38:49 pm
content: thanks for the tips.Unfortunately, I can do only 2 layers board.attached my 2 attempts:1.jpg: top for gnd and signals, bottom for psu rails and only 1 short signal trace.. can't do in a different way.2.jpg: top for signals, bottom for psu rails and gnd pour (some errors here and there to be fixed).on the left and top the analog section, on the right the digital one.which way should I go?

author: Someone
author_rank: Super Contributor
timestamp: January 22, 2018, 08:29:55 pm
content: Quote from: firstcolle on January 22, 2018, 12:38:49 pmUnless you really know what you are doing, don't split the grounds. Pour the ground on the top and bottom layers and then stitch them together with vias.

author: fcb
author_rank: Super Contributor
timestamp: January 22, 2018, 11:19:08 pm
content: Personal preference would be one solid ground on both sides for double sided.It looks like you have already put the effort into the split unit. So I'd be tempted to commission two versions (1) as you have it and (2) with a single solid plane both sides with plenty of stitching vias. Not much effort or expense - have a listen/measure both and see which you prefer.