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Old 3rd October 2004, 02:28 AM   #1
los_ren is offline los_ren  United States
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Default 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
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Old 3rd October 2004, 10:44 AM   #2
Tor M is offline Tor M  Norway
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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
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Old 3rd October 2004, 02:32 PM   #3
los_ren is offline los_ren  United States
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"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
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Old 4th October 2004, 06:27 PM   #4
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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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Old 4th October 2004, 09:18 PM   #5
los_ren is offline los_ren  United States
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no i know, but question answered i found my quote to be more interesting in context of my project =]
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