How Low Can You Go?

Dec 22, 2010 2 Replies

I need to cram a TL499AC converter circuit into the smallest, tightest, area possible so I want to use 1/10 watt resistors. Assuming I get maximum power drain from the circuit that the convertor will power, possibly as much as 600 ma (or whatever's the maximum the converter is capable of), wll thesy tiny resistors be okay?



Ron



Does your simulation show that the power dissipated by each resistor will always be significantly less than the maximum permissible, (after derating to accommodate the highest local temperature and resistance tolerance extremes), in each resistor in question?

See the paragraph that starts with "Note that the nominal power rating .." in:

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If so, yes. If not, you get to provide a way to cool the assembly and / or use components capable of dissipating that power safely.

--Winston

You can do this in five easy steps:

  • Figure out the voltage across, or current through, each resistor
  • Use that, plus the resistance, to calculate the resistor power dissipation.
  • Derate appropriately, per the resistors that you intend to use and your local ambient.
  • Choose resistors accordingly.
  • Enjoy

IIRC, 0603 resistors are generally 1/16th watt, so 1/10th watt resistors are no big deal these days.

Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html

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