LM3886 Chip Pin 7 Grounding - diyAudio
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Old 1st June 2011, 02:44 PM   #1
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Default LM3886 Chip Pin 7 Grounding

Hi guys,

I have (yet another) LM3886 grounding question.
Yep, I've read all the posts I can find on grounding this chip!

I'm building an LM3886 amp, using a PCB based on the datasheet (non-inverting layout, including zobel network), with separate ground traces, and separate ground wires running back to a big central star ground.

All well and good so far ;-)

So, quoting the datasheet :
"Return the load ground, the output compensation (zobel) ground, and the low level ground to the common ground point through separate paths."

I have no problem with that, in so far as it goes.

But this leaves me with two questions on grounding :

1) What do people advise for the *chip* ground (pin 7) ?
Another separate return to the star ground?
Tying it into the local PSU ground?
Tying it into the local low level ground?

2) A less important question... is there any benefit in splitting the low level grounds into separate ground returns? Separate input and feedback? Or is this irrelevant (or detrimental)?


Thanks for your thoughts!
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Old 2nd June 2011, 04:49 PM   #2
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According to its function it belongs to the low level ground and that is also how National reference designs deal with it.

In the low level section the advantage of short paths is bigger than the advantage of keeping currents separate. The currents there are very small so they won't lead to big differences in ground potentials even if they add up. Separate ground returns don't make much sense there, although the differences will be small either way.
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