Some PCB GND layout questions - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th January 2013, 10:13 AM   #1
diyAudio Member
 
Join Date: Sep 2012
Default Some PCB GND layout questions

Hi,

I'm a beginner regarding PCB layout. My plan is to learn about PCB design by making a small amp with IC like LM1875 or equivalent.

What is the best way for ground layot? I made 2 examples for the powersupply part and was wondering which is best. Also where do I connect small signal ground? To one of the existing ground lines or do I have to run a seperate one to the GND connector?

Tips would be highly appreciated..
Attached Images
File Type: jpg 1.JPG (120.0 KB, 241 views)
File Type: jpg 2.JPG (119.6 KB, 237 views)
  Reply With Quote
Old 30th January 2013, 05:57 AM   #2
diyAudio Member
 
dchisholm's Avatar
 
Join Date: Mar 2011
Location: St Louis, Mo
I like your second example better than the first. The central vertical trace establishes a single ground for both sides of the supply. In your first example, the two sides of the supply can have different "ground" reference potentials at the IC.

In general you will separate signal ground from power ground and connect them at only one point in the circuit - sometimes called the "star ground" point. The Application Notes for your particular IC, and any threads about it on this Forum, may have suggested examples of how to do this.

Dale
  Reply With Quote
Old 30th January 2013, 07:58 AM   #3
CBS240 is offline CBS240  United States
diyAudio Member
 
CBS240's Avatar
 
Join Date: Aug 2005
Location: K-town
It is also worth having a simple CRC filter, or CRCCcc. The key is to have seperate return current paths for the first 'C' than those for the second 'C', the one that actually powers the amplifier. The GND return for the second 'C' would be where the speaker and decoupling would go. The center tap of the transformer would be at the junction of the first set of caps, and then a single seperate GND connection to the other set of caps and the main star GND for the amplifier circuit. This keeps the pulse currents from the 60Hz (120Hz) power input AC seperate from the GND return currents from the amplifier driving the speaker.
__________________
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 30th January 2013, 10:54 AM   #4
diyAudio Member
 
Join Date: Sep 2012
Thanks for the replies

Very useful information. I have added some traces to the PCB, hope this is OK.
Attached Images
File Type: jpg 3.JPG (165.6 KB, 179 views)
  Reply With Quote
Old 6th April 2013, 07:09 AM   #5
diyAudio Member
 
Join Date: Sep 2012
I got some time to practice my PCB layout skills and came up with this design. It is a LM1875 amp on steroids, with 2 extra transistors.

Any recommendations regarding the layout would be highly appreciated.
Attached Images
File Type: jpg LM1875_50w.JPG (891.7 KB, 138 views)
  Reply With Quote
Old 6th April 2013, 08:14 AM   #6
diyAudio Member
 
Join Date: Jun 2011
If I had to use dual layer pcb for that, I probably would consider to make every trace on one layer and reserv the other one completely as a groundplane???
Then even put a capacitor bank on the same pcb...
  Reply With Quote
Old 6th April 2013, 08:19 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
post4 is better.
Can you remove or reduce the loop areas of the +ve & return?
Same for loop of -ve and return.

Remember that in EVERY circuit there is a source voltage that drives the current out, or away, in the FLOW route and that current MUST come back in the RETURN route.
The loop formed by that flow and return MUST be kept small.
__________________
regards Andrew T.
  Reply With Quote
Old 6th April 2013, 12:51 PM   #8
alex mm is offline alex mm  Romania
diyAudio Member
 
alex mm's Avatar
 
Join Date: Mar 2006
Location: Baia Mare ,
....... single side PCB without steroids and power supply , only schematic from data catalog ......
Regards Alex.
Attached Images
File Type: jpg PCB LM1875 ALL.JPG (749.4 KB, 120 views)

Last edited by alex mm; 6th April 2013 at 12:57 PM.
  Reply With Quote
Old 6th April 2013, 01:27 PM   #9
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Paris
The big problem I see with the layout in post 5 is that the small sensitive groundplane in blue is tied to the AC ground terminal coming from the transformer. It's the worst place to connect it, as heavy charging currents run through that point. Put that groundplane back to the "green layer" and simply tie it to the main groundplane.

Even with a groundplane, it is good to think in term of a power bus when laying things down physically.

edit: CBS240 already gave a detailed explanation on the reasons why.
__________________
Ben.

Last edited by 00940; 6th April 2013 at 01:30 PM.
  Reply With Quote
Old 6th April 2013, 02:01 PM   #10
diyAudio Member
 
Join Date: Sep 2012
Thanks for the tips.

So now I changed the ground and power layout as a starting point.


And tie the sensitive signal ground plane to the top part of the ground plane near the small 100n capacitors, right?
Attached Images
File Type: jpg LM1875_50w_2.jpg (416.5 KB, 78 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Eagle vs. Sprint-Layout for PCB design/layout hollowman Parts 11 12th January 2014 09:01 PM
Elements between PCB-GND and Mains Earth in SolidState Power Amps - How to Calculate? tiefbassuebertr Solid State 39 2nd July 2012 05:45 PM
SMPS Gnd, Chassis-Gnd, and Layer Stack gearheadgene Power Supplies 1 5th July 2011 12:00 PM
PCB Layout Questions buzz1167 Solid State 24 9th October 2010 06:55 PM
PSU PCB Layout questions cliffD Digital Source 0 25th May 2006 06:12 PM


New To Site? Need Help?

All times are GMT. The time now is 12:03 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2