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.
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:
What do you think? Is it ok?
If anyone like to have the files just let me know!
/Adam
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.
An externally hosted image should be here but it was not working when we last tested it.
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:
An externally hosted image should be here but it was not working when we last tested it.
What do you think? Is it ok?
If anyone like to have the files just let me know!
/Adam
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
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
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
You may want to check out the LM3886 Bypassing Revisited Thread.
~Tom
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