| samsagaz |
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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| samsagaz |
well take a look at this.. it will work? the design in not good, i know. :(
at least tellme some tips it looks terrible :D |
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| jackinnj |
| 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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| samsagaz |
well thanks dude, ill try to use 150 mills in my power tracks...
btw, i forgot to add the image in my other post :D
please dont "LOL".... its my first design im new on this... |
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| jackinnj |
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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| samsagaz |
| i cant do double side boards. ill try to start other pcb tomorrow. |
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| jackinnj |
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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| samsagaz |
| 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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| peranders |
| 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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| samsagaz |
thanks guys....
and thanks for the email peranders :D |
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| samsagaz |
what abt this PCB? how this looks like?
can someone fix me few things? :D |
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| jackinnj |
| you have to remember that the components need clearance for the heatsink. Not a good idea to mount a resistor, capacitor or connector on the back-side of the LM3886, LM3875 or LM4780. |
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| SheldonD |
Sam: I am confused with your pcb
your pcb has 11 pin connections showing, 4780 has 27 pins |
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| jackinnj |
| Shel -- he is working with the 3875 or 3886 -- the point I was trying to make is that you don't have any room for resistors, etc. on the "mounting" side of the operational amplifier due to the clearance for the heatsink. -- |
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| samsagaz |
oh, yes, its the pcb for the lm3886, its easy than the 4780 (at least have half of pins) :D
im making both PCB one for 4780 and other for 3886, i think that 3886 is a little easier than 4780
ok, ill move the resistor/cap
any other comment? |
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