Quote Originally Posted by irving2008 View Post
Eddy, I didnt miss the point - if its a motor controller is not dissipating 60w continuously, as its almost certainly a PWM arrangement. Its only dissipating that wattage during the 'on' cycle at a high frequency. take for example a common controller chip from ST. Its capable of 30A without a heatsink... but thats because the switching frequency is 10khz. for a single pulse at that frequency the thermal characteristic is <0.1degC/W so a heatsink of only 16sq cm of copper on the PCB will suffice to keep the mean junction temperature below 125degC. You could never run a linear circuit at that sort of load. The actual static chip thermal resistance is typical at 15decC/W... at 60W the jiunction temp would be 15*60deg over ambient = 900deg... it would have long since melted!

For the record I have designed systems for both miltary (-55 -> +125degC) and space applications (-100 -> +250degC)!
I assume you are referring to the VNH3SP30. This chip cannot handle 30A without a heatsink. It's thermal protection kicks in when more than 8A continuous is output using the small PCB footprint. It has a PWM input capable of 10K but it is supplied externally, fully under the control of the user. There is no internal PWM capability. This IC switches high and low side power MOSFETs as instructed by the inputs and PWM may be used if you chose to use it.

Again, my point is that airflow over the chip is much more efficient at dissipating heat than a hunk of metal.

Eddy