AX3500 vs. AX3500BP Thermal Performance

I\'ve been using two AX3500s to control the drive motors on a mobile robot and have occasionally seen the controllers go into a cutback mode when operating in warmer temperatures. I have been able to work around this simply by placing small fans inline with the heatsinks, but this is undesirable as a long-term solution.

Looking at the specs for the 3500 vs. the 3500BP, it looks like the BP will sustain larger currents for longer periods of time, which suggests to me that the conduction plate transfers heat away from the MOSFETs more efficiently than the heatsink. Is this true? Or is their some other difference between the two that I\'m not seeing?

Also, do the better performance numbers for the 3500BP assume that the conduction plate is mounted flush to a chassis?

Finally, would it be possible to connect a Peltier cooler to the conduction plate to provide more heat dissipation?

The plate does a better job than the heatsink. It has a larger surface overall. It is better with the plate in free air but if you can have the plate mounted on a large metalic surface, this is even better.

Peltier cells can help but they work as long as you can dissipate the heat at the other end of the cell. They do burn a lot of current, however.