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Old 5th August 2005, 04:23 PM   #1
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Default Single sided lm3886 board, opinions?

Hello!

Was a bit bored this morning so i sat down and tried to learn how to use Eagle. Wasn't too hard i think so i made a board based on carlosfm's schematic; non-inverted version 3.

Click the image to open in full size.

I made the board single sided so it's easy to make it yourself. I'm using parallelled 1 ohm resistors instead of 0,47 ohm because I can't get any good resistors below 1 ohm (don't want to use wire wound ones). This way they won't get too hot. Anyway here is the result:

Click the image to open in full size.

What do you think? Is it ok?

If anyone like to have the files just let me know!

/Adam
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Old 15th March 2014, 07:16 PM   #2
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Adam,

I'll be extremely delighted to receive the PCB files.

Thanks,
Ramdass.
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Old 16th March 2014, 06:56 PM   #3
gfiandy is offline gfiandy  United Kingdom
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The layout is neat and tidy and mostly makes sense, I have made a few comments below.

Is the intention that the input and power grounds are connected at the PSU as you have not connected them together on the pcb. If you do want to connect the input ground the best spot would be the centre of the track that connects the grounds on the two bulk storage caps.

My experience of the lm3886 would lead me to think this design might suffer slight instability under heavy loads into 4R as the bulk storage caps are a fair distance away and normally you need 22uf almost on the pins to keep these stable. However the damping circuit might resolve this I have not investigated this approach.

The output current flows very close to the input cap this could cause positive feedback under heavy loads as the current could induce a voltage on the input cap. Also it would be better if the output ground connected in the centre of the track between the two bulk storage caps a mismatch in the impedance for the return current can induce low level distortion.

Having said all this in normal operation it will probably work fine these chips are fairly forgiving till you get to high loads.

Regards,
Andrew
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Old 25th March 2014, 12:32 PM   #4
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Thanks, Andrew for your comments on Adams layout.

I too wanted to try using Eagle and found what Adam said was true! It is fairly easy.

I have attempted to address the concerns raised by you. Please feel free to comment on my layout attempt.

Regards,
Ramdass
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Old 25th March 2014, 11:58 PM   #5
tomchr is offline tomchr  United States
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C4 and C5 need to be as close to the IC pins as possible. I see no use for C3.

You may want to check out the LM3886 Bypassing Revisited Thread.

~Tom
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Old 26th March 2014, 03:18 PM   #6
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Thanks Tom for your valuable comments. I did check out your posts on Bypass and found them very interesting. I am attempting to redo my layout.

This is an attempt after a long gap of about more than 20 years in PCB layout designing.

Ramdass
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