Simple LM4780 question...

los_ren · 3rd October 2004, 02:28 AM

im making a PCBs for a bridged/parallel dual LM4780 setup. Class project. question is, can the NC pins on the LM4780 be in contact with GND? it makes routing the power to the chip much easier if this isnt an issue.

thanks for your time.

rmr

Tor M · 3rd October 2004, 10:44 AM

Hi!

Have a look at this page:

http://home.pacific.net.au/~gnb/audio/lm4780.html

I think this answers your question.

Regards

Tor Martin

los_ren · 3rd October 2004, 02:32 PM

"LM4780 is a dual LM3886

The LM4780 package contains two LMP3886AT silicon dice. This is the same die as used in the LM3886.

LM3886 design procedure and schematics may be applied to the LM4780, with a slight derating of 0.5 dB in the nominal output power, from 68 Watts down to 60 Watts per channel."

heh, that helps alot. the schematic i used to design the PCB is from a national semiconductor bridged/parallel LM3886 application notes pdf. kinda saves a bit of worrying if the schhematic would be compatible.

i was going to cut the NC pins like suggested on another thread, but the idea kinda bothered me.

thanks alot =D

ken.berg · 4th October 2004, 06:27 PM

Perhaps you should have read ALL the way through the referenced URL to the answer to your question:

The "NC" pins are truely "No Connection"
Pins 1, 3, 6, 13, 23, 24 and 26 are designated as "NC" or "No Connection". In existing published designs and the reference design in the National Semiconductor data sheet, these pins are variously connected to V+, GND and nothing. There is actually no particular electronic design requirement for them to be connected to anything at all, as the pins are independently mounted in the insulated packaging and have no internal connection.

They may be safely connected to any other pin or left unconnected.

As a design aid, they can be connected to adjacent pins to make PCB tracks wider for the power supply rails, or used as a "via" to carry PCB tracks from one row of pins through the second row of pins to other components.

los_ren · 4th October 2004, 09:18 PM

no i know, but question answered i found my quote to be more interesting in context of my project =]

3rd October 2004, 02:28 AM	#1
los_ren diyAudio Member Join Date: Jun 2004 Location: Independent Republic of California	Simple LM4780 question... im making a PCBs for a bridged/parallel dual LM4780 setup. Class project. question is, can the NC pins on the LM4780 be in contact with GND? it makes routing the power to the chip much easier if this isnt an issue. thanks for your time. rmr __________________ :: when they kick at your front door, how you gonna come? with your hands up on your head, or on the trigger of your gun... when the law break in, how you gonna go? shot down on the pavement, or waiting on death row...

3rd October 2004, 02:32 PM	#3
los_ren diyAudio Member Join Date: Jun 2004 Location: Independent Republic of California	"LM4780 is a dual LM3886 The LM4780 package contains two LMP3886AT silicon dice. This is the same die as used in the LM3886. LM3886 design procedure and schematics may be applied to the LM4780, with a slight derating of 0.5 dB in the nominal output power, from 68 Watts down to 60 Watts per channel." heh, that helps alot. the schematic i used to design the PCB is from a national semiconductor bridged/parallel LM3886 application notes pdf. kinda saves a bit of worrying if the schhematic would be compatible. i was going to cut the NC pins like suggested on another thread, but the idea kinda bothered me. thanks alot =D __________________ :: when they kick at your front door, how you gonna come? with your hands up on your head, or on the trigger of your gun... when the law break in, how you gonna go? shot down on the pavement, or waiting on death row...

4th October 2004, 09:18 PM	#5
los_ren diyAudio Member Join Date: Jun 2004 Location: Independent Republic of California	no i know, but question answered i found my quote to be more interesting in context of my project =] __________________ :: when they kick at your front door, how you gonna come? with your hands up on your head, or on the trigger of your gun... when the law break in, how you gonna go? shot down on the pavement, or waiting on death row...

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3rd October 2004, 10:44 AM	#2
Tor M diyAudio Member Join Date: Oct 2002 Location: Haugesund	Hi! Have a look at this page: http://home.pacific.net.au/~gnb/audio/lm4780.html I think this answers your question. Regards Tor Martin

4th October 2004, 06:27 PM	#4
ken.berg diyAudio Member Join Date: Nov 2003 Location: Tempe, AZ	Perhaps you should have read ALL the way through the referenced URL to the answer to your question: The "NC" pins are truely "No Connection" Pins 1, 3, 6, 13, 23, 24 and 26 are designated as "NC" or "No Connection". In existing published designs and the reference design in the National Semiconductor data sheet, these pins are variously connected to V+, GND and nothing. There is actually no particular electronic design requirement for them to be connected to anything at all, as the pins are independently mounted in the insulated packaging and have no internal connection. They may be safely connected to any other pin or left unconnected. As a design aid, they can be connected to adjacent pins to make PCB tracks wider for the power supply rails, or used as a "via" to carry PCB tracks from one row of pins through the second row of pins to other components.

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