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Old 6th September 2004, 12:03 AM   #1
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Default how mils for me PCB?

hey guys, im designing my first amp using lm4780, im drawing t he PCB using protel, can someone tellme how many mils will be ok for the GND and V+ and V- tracks?


how can i calculate it?
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Old 6th September 2004, 02:38 AM   #2
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well take a look at this.. it will work? the design in not good, i know.

at least tellme some tips it looks terrible
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Old 6th September 2004, 03:23 AM   #3
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National has a prototype/evaluation board drawing on their website -- it's also in the back of the product PDF -- start thinking in the vicinity of 150 mils.
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Old 6th September 2004, 03:40 AM   #4
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well thanks dude, ill try to use 150 mills in my power tracks...


btw, i forgot to add the image in my other post

please dont "LOL".... its my first design im new on this...
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Old 6th September 2004, 03:58 AM   #5
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The Overture Design chips aren't quite so user friendly in some of the pin assignments. You can get the peak current requirements from the Excel worksheet that National Semiconductor supplies. If you can't do double-sided boards consider running power jumpers with #18 wire -- it's just a short distance so R * I^2 losses aren't enough to worry about.

Do take a look at the XRay diagrams in the PDF.
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Old 6th September 2004, 04:20 AM   #6
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i cant do double side boards. ill try to start other pcb tomorrow.
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Old 6th September 2004, 04:35 AM   #7
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another trick with the Overture series is to snip the unused and unconnected leads from the chip to the board -- this might give you some more space to work with.

i very rarely make double-sided boards -- life is too short. all of my double sided boards are sent out to a prototype house (and come back in a couple days)

I make most of my boards with copper on top -- when I print the design I make an additional paper copy and use a red marker to place jumped locations -- as my PCB design program assigns Green to the top and Red to the bottom. Tou should be able to turn the top and bottom layers off in most PCB design programs.
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Old 6th September 2004, 11:34 AM   #8
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well im trying to use 150 mils for gnd and v+ and v- and looks that its too hard to do it
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Old 6th September 2004, 02:07 PM   #9
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look at page 22:
http://cache.national.com/ds/LM/LM4780.pdf
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Old 6th September 2004, 02:22 PM   #10
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Quote:
Originally posted by samsagaz
well im trying to use 150 mils for gnd and v+ and v- and looks that its too hard to do it
If you are going to make a singlesided pcb you must make the pads bigger. Make them a big as you can, if not they will come loose.

150-200 mil is OK for power, 20-40 is OK for signal traces.
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