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Old 24th February 2005, 01:20 PM   #11
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Doh! thanks guys, I appologize for the silly mistakes I should have double checked the art work again.
I am currectly reading the snubber thread thrying to figure out what I should be doing. But I don't have an L on the baord, should I?
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Old 24th February 2005, 01:31 PM   #12
Alcaid is offline Alcaid  Norway
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Just remember that the trace after your output resistors will carry twice the current. Output current limit for the LM4780 is 11.5A each channel. 23A peak, but the trace won't dissipate more than RMS (23A/sqrt(2) = ) 16.3A.

Use the Overture Design Guide 1.5 located here to see what current the traces must handle at your supply voltage.
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Old 24th February 2005, 09:14 PM   #13
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I tried to use the calculators, it's a lot more involved than I first thought and I still have to figure out how heavy my boards are I'm going to use. I guessed at 1oz at least it's a safe assumption. A couple of things I gleaned from the National data sheet, firstly I can make short "nubs" from pins to tie my much heavier tracks to like I did for the outputs. Also my trace after the power resistors needs to be huge so I just laid down the biggest feasible area to minimize resistance and act as a heat sink.

Would an 18V dual secondry transformer make more sense? This will go into 4 ohms, it would bring my current and heat sinking requirements to something much more realiastic.
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