lm4780 project

laki101 · 9th November 2010, 07:55 PM

thinking of making a amp using the lm4780 in bridge/parallel (I am asking you which would you recomend) config like in the datasheet http://www.national.com/ds/LM/LM4780.pdf page 5/6
now I am not sure how to wire it so could you please just write me which pin do i connect and where actually I am just not sure do I need to all V+ to +rail etc. or is just one enough and what are the NC pins?

and does any one have any experience with this chip

MJL21193 · 9th November 2010, 07:59 PM

Lm4780 + bridge/parallel + "I am not sure how to wire it" = maybe you should start with something a bit less complicated.

AndrewT · 11th November 2010, 12:48 PM

no "maybe" about it.

Learn on something much simpler.
Read and copy good design with lot's of support.
Decibel Dungeon is a good source with support.

random007 · 12th November 2010, 09:44 PM

Quote:

Originally Posted by laki101

thinking of making a amp using the lm4780 in bridge/parallel (I am asking you which would you recomend) config like in the datasheet http://www.national.com/ds/LM/LM4780.pdf page 5/6
now I am not sure how to wire it so could you please just write me which pin do i connect and where actually I am just not sure do I need to all V+ to +rail etc. or is just one enough and what are the NC pins?

and does any one have any experience with this chip

The 4780 is two identical 3886 chips in one package. Some pins are shared and others aren't. Yes, you should wire up multiple voltage pins not just one of each. NC = not connected. These can even be snipped off... if you're sure you have the right ones.

As said, try a simple amp first and learn how it works and what various necessary and optional components do and how to wire them all up.

erky01 · 12th November 2010, 10:49 PM

Connect all of the V+ to the positive rail, and all of the V- pins to the negative rail. You can't assume those bond pads are connected inside the IC package or silicon die with a low resistive path. You run the risk that some parts of the internal circuit are powered up, and others are not. Even if they were connected internally, now all the current drawn by the device is concentrated on one pin, and that pin might get hot enough to melt the solder joint.
NC stands for no connect, don't connect these pins to anything else.

9th November 2010, 07:55 PM	#1
laki101 diyAudio Member Join Date: Dec 2009	lm4780 project thinking of making a amp using the lm4780 in bridge/parallel (I am asking you which would you recomend) config like in the datasheet http://www.national.com/ds/LM/LM4780.pdf page 5/6 now I am not sure how to wire it so could you please just write me which pin do i connect and where actually I am just not sure do I need to all V+ to +rail etc. or is just one enough and what are the NC pins? and does any one have any experience with this chip

11th November 2010, 12:48 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	no "maybe" about it. Learn on something much simpler. Read and copy good design with lot's of support. Decibel Dungeon is a good source with support. __________________ regards Andrew T.

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9th November 2010, 07:59 PM	#2
MJL21193 Account disabled at member's request Join Date: Mar 2007	Lm4780 + bridge/parallel + "I am not sure how to wire it" = maybe you should start with something a bit less complicated.

12th November 2010, 10:49 PM	#5
erky01 diyAudio Member Join Date: Sep 2008	Connect all of the V+ to the positive rail, and all of the V- pins to the negative rail. You can't assume those bond pads are connected inside the IC package or silicon die with a low resistive path. You run the risk that some parts of the internal circuit are powered up, and others are not. Even if they were connected internally, now all the current drawn by the device is concentrated on one pin, and that pin might get hot enough to melt the solder joint. NC stands for no connect, don't connect these pins to anything else.

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