Yet another LM3886 PCB - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 11th November 2004, 11:45 PM   #1
Tim__x is offline Tim__x  Canada
diyAudio Member
 
Join Date: Jun 2004
Location: Edmonton area, Alberta
Question Yet another LM3886 PCB

How does it look? It's an IGC, I plan on soldering the NFB resistor directly to the chip. Should I connect the grounds together on board like this?

Also, does anyone know of any good (read cheap) boardhouses in canada? A walkthrough of how to order boards would also be nice, like what files I need to send them, how to make said files, etc.
  Reply With Quote
Old 11th November 2004, 11:47 PM   #2
Tim__x is offline Tim__x  Canada
diyAudio Member
 
Join Date: Jun 2004
Location: Edmonton area, Alberta
Sorry, attachment trouble.
Attached Images
File Type: gif lm3886.gif (20.8 KB, 785 views)
  Reply With Quote
Old 13th November 2004, 09:05 PM   #3
Tim__x is offline Tim__x  Canada
diyAudio Member
 
Join Date: Jun 2004
Location: Edmonton area, Alberta
125 Views and no reply?

Bump!
  Reply With Quote
Old 13th November 2004, 10:19 PM   #4
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
Devices, which produce heat, such as output resistor in this case, must have distance all around. Warm resistor can burn neibour, remember on this .
  Reply With Quote
Old 13th November 2004, 10:27 PM   #5
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
The signal ground path should be re-arranged and not connected as you did.

Separate the grounds. Do a separate path to a mid ploint between power ground and signal ground and make that your star.

That should clean it.


Carlos
  Reply With Quote
Old 13th November 2004, 10:40 PM   #6
Tim__x is offline Tim__x  Canada
diyAudio Member
 
Join Date: Jun 2004
Location: Edmonton area, Alberta
As it is, the signal ground and power ground meet at the ground pin, no power current will go through the signal ground, so in effect it is star grounded. Yes?

What's wrong with the signal path? Too close to the output? How should I change it? Note the "IN1" is the signal ground and the loop is meant as a guard trace.

Thanks Upupa Epops, I will give the output resistor a little space.
  Reply With Quote
Old 14th November 2004, 03:56 AM   #7
captain is offline captain  United States
diyAudio Member
 
Join Date: Oct 2004
I'm starting to try to learn this PCB stuff too. It would be nice if they had a whole separate forum devoted to the subject dealing with theory...software...PCB houses...etc.

I'm laying out a LM4782 3-channel PCB...but it's non-inverted. I'm using the schematic at the end of the data sheet. I looked at the "LM4782 inverted schematic" to get the gist of "inverted" layouts. Although, yours is different.

Anyway, assuming your schematic is correct...and in my ignorance...why wouldn't you do the following:

As the trace comes out the bottom of resistor #1 then immediately take it straight "west" to meet up with ground.

Also, leave the trace coming out the "west side" of IN1 (signal ground)...so it meets up with ground.

Then get rid of everything on the east side of IN1 including that part the comes down from resistor #1 and the part that loops around...I believe you refered to is as a "guard trace".

Maybe you can explain to me what a guard trace is.
Please, forgive this noobe...

By the way, I've done a lot of Googling to try an find a good deal on PCB fabrication.

It seems like www.PCBFabExpress.com has the best deal by far. Anything up to a 20 square inch board goes for 13 USD (minimum order of 5 boards). That includes 2oz. copper double sided, both side solder mask, and silk screen printing on the top side. They also have a "barebone" option. You have to do the math to see what is the better deal.

This company has a rather interesting concept. They are essentially aggregators. Their engineers work out of their homes. They take individual orders and "panel them up" into large panels. Then they contract with a number of fabricators (in silicon valley with ISO-9002 certification) to make the boards. Then, they have their own on-site employees do a quality check before shipping the finished boards out to the customer.

With the telecom and internet bust, I think the PCB industry became oversaturated, especially in Silicon Valley. These guys have figured out a "middleman niche" to leverage that excess capacity.

They've made it so that the big production outfits don't have to deal with a bunch of little orders. In fact their engineers don't have to be involved at all. They're just getting full gerber files for doing full large panels. The last step being routing out all the small boards. Then the on-site employees take the boards from there.

So PCBFabExpress doesn't have any capital tied up in plant or equipment. If one fabricator messes up...there are dozens of others across Silicon Valley needing to fill up excess capacity.

The only gotcha in using their service is that you must provide them with Gerber 274X files for your PCB. This has become the "generic format".

Tim_X...it looks like you are using some kind of layout software. What software are you using? Maybe it will output this format.
If not, I may have a recommendation as to some good software that does ($50 USD).

I have never had any boards fabed yet. Maybe someone has delt with these people.

Anyway...I've droned on long enough...

...Good luck on your project...
  Reply With Quote
Old 14th November 2004, 09:30 PM   #8
diyAudio Member
 
Join Date: Sep 2003
Location: Illinois
Quote:
Originally posted by captain

It seems like www.PCBFabExpress.com has the best deal by far. Anything up to a 20 square inch board goes for 13 USD (minimum order of 5 boards). That includes 2oz. copper double sided, both side solder mask, and silk screen printing on the top side. They also have a "barebone" option. You have to do the math to see what is the better deal.

Olimex (www.olimex.com) has boards for about $25 bucks with only one piece. And they take eagle files, so you can get eagle for free and have the boards made by them.
  Reply With Quote
Old 15th November 2004, 12:46 AM   #9
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Quote:
Originally posted by carlmart
The signal ground path should be re-arranged and not connected as you did.
Tim, this is good advice.
Power ground should stop on the film bypass caps, C3 and ? (reference not clear).
  Reply With Quote
Old 15th November 2004, 08:29 PM   #10
Tim__x is offline Tim__x  Canada
diyAudio Member
 
Join Date: Jun 2004
Location: Edmonton area, Alberta
I'm using Eagle, it's freeware.

The guard trace just provides some extra isolation from the other traces on board, it's not really needed, but their was no reason not to so...

What's wrong with my signal path? Carlmart? Carlosfm?

Quote:
Power ground should stop on the film bypass caps, C3 and ? (reference not clear).
It's C6, and I don't agree with you here, the purpose of the bypass caps is to keep the supply pins low impedance at high frequencys, so they should be connected as close as possible to the IC pins.

Or are you saying pin 7 should only connect to signal ground?
  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
My First LM3886 GC samsagaz Chip Amps 49 29th June 2008 07:55 PM
Psu Lm3886 Mayday Chip Amps 29 29th April 2007 06:10 PM
Lm3886 Bpa Tombson Chip Amps 99 21st August 2006 12:04 PM
Are two separate lm3886 = 2*lm3886 in parallel or bridge mode rs1026 Chip Amps 11 21st October 2004 10:24 AM


New To Site? Need Help?

All times are GMT. The time now is 02:58 PM.


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