On the 30 amp hbridge - what is the best way to heatsink it? Will I get better heat dissipation from the top of the chip or from the underside of the board? Should I do both? The motor will stall at 18amps. Usually it’ll be running in the 2-3amp range.
You could use some thermal epoxy to glue a heat sink to the top of the chip. We have gotten about 18A for several minutes with a heat sink on top of the chip. You could add a heat sink to the bottom of the PCB, but you would have to be careful not to create any shorts between the various traces and pads there.
Are you having problems with the motor driver without heat sinks? You don’t have to use a heat sink if the chip is not overheating, and it does shut down if overheated, which might be useful since excess heating could be an indication of your motor stalling. It would be better to have the motor driver overheat and shut down than to have the motor driver keep delivering the current until the motor (or something else) breaks.
Thanks for the quick reply. I haven’t actually profiled the motor driver in the application yet. I was actually planning to thermal-epoxy the board to a flat steel plate on the gear of the motor as a dodgy heat-sink and convenient mounting location and wanted to know which side would be better to attach. I was favoring the top of the chip glued to the plate and the bottom of the board facing air, perhaps with a mini-heat sink on it. I never thought about thermal cut-off as a positive feature beyond saving the chip itself. Might be a good idea.