Using Copper Traces As Ballast Resistors Ensures Balance

Focus:

When paralleling the LT3080 linear regulator, using pc board traces as ballast resistors is economical because it eliminates the cost of current-sense resistors. However, there are additional benefits such as the elimination of solder joints and the high, positive temperature coefficient of copper pc board traces. The high temp coefficient can be used to promote equal current sharing and heat dissipation among paralleled regulators. This technique can also be used in other applications with ballast resistors such as bipolar transistors.

What you’ll learn:

• How to use pc board traces as ballast resistors to promote current sharing and distribution of heat dissipation
• How to exploit the positive temperature coefficient of pc board traces used as ballast resistors

Notes:

ED's Ideas For Design. Also see Bob Dobkin's video about the LT3080, "Direct Paralleling, High Power Density LDO" at http://www.youtube.com/watch?v=xbDHnalm-MQ

View the Source

Author & Publication:

Tom Bruhns, design engineer, Agilent Technologies, Everett, Wash., Electronic Design, Nov 17 2008

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