Simple LM4780 Question

sam9 · 27th November 2005, 02:50 PM

I could answet this in about 30 seconds if I had one sitting in front of me, but I don't.

Here it is: The pin-out diagram on the LM4780 shows two pins labled "GND". Is there continuity between these or not? I.e., is there an independant ground for each device in the package?

Peter Daniel · 27th November 2005, 03:34 PM

The GND (pin 12 and 19) are not internally connected.

sam9 · 27th November 2005, 03:58 PM

Thanks. That is good to know (and what I was hoping to hear).

sam9 · 27th November 2005, 04:03 PM

Not being real awake yet this morning, I forgot to as further which GND pin serves device A and which B. From the pinout diagram I would guess pin 12 is most likely A and 19 B, but there is no certainty of that.

Peter Daniel · 27th November 2005, 04:08 PM

I can't be sure of that either, as in my implementation both grounds are connected anyway so I didn't really investigate that issue.

sam9 · 27th November 2005, 06:29 PM

I can work that out when the pieces arrive. The intent is for an HT amplifier (Lm4780x3 +LM3886x1). With everything all on one PCB my thought was that every effort to keep each channel as isolated as possible would be a good idea especially as it will double for ordinary music playback as well. I think I will have to see what kind of mess results when I lay out the PCB -- whether independant grounds or a single common one is more practical. Power bypass ground will definately be a separate net, however.

27th November 2005, 02:50 PM	#1
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Simple LM4780 Question I could answet this in about 30 seconds if I had one sitting in front of me, but I don't. Here it is: The pin-out diagram on the LM4780 shows two pins labled "GND". Is there continuity between these or not? I.e., is there an independant ground for each device in the package?

27th November 2005, 03:34 PM	#2
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	The GND (pin 12 and 19) are not internally connected. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

27th November 2005, 04:08 PM	#5
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	I can't be sure of that either, as in my implementation both grounds are connected anyway so I didn't really investigate that issue. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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27th November 2005, 03:58 PM	#3
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Thanks. That is good to know (and what I was hoping to hear).

27th November 2005, 04:03 PM	#4
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Not being real awake yet this morning, I forgot to as further which GND pin serves device A and which B. From the pinout diagram I would guess pin 12 is most likely A and 19 B, but there is no certainty of that.

27th November 2005, 06:29 PM	#6
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	I can work that out when the pieces arrive. The intent is for an HT amplifier (Lm4780x3 +LM3886x1). With everything all on one PCB my thought was that every effort to keep each channel as isolated as possible would be a good idea especially as it will double for ordinary music playback as well. I think I will have to see what kind of mess results when I lay out the PCB -- whether independant grounds or a single common one is more practical. Power bypass ground will definately be a separate net, however.

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