The better way to design for your task would be to use a MOSFET H-Bridge, as MOSFETs have a very low on resistance, on the order of milliohms. 2.5V X 1.4A means the chip has to dissipate 3.5 Watts of heat.
Yes that is normal that it would get roasting You need a heatsink at that current or the chip will die soon. Jonathan, hope this will help with your UK version! The schematic for this is exactly the same as the one on page 14 of the ST datasheet, with the addition of an LM7805 regulator for the power, a few caps and a reverse-polarity diode. The whole unit is about one inch by two inches by four inches. There are also blobs of epoxy and hot glue on all the hardware, since a loose screw inside something once cost me thousands of dollars and a couple of plane flights to fix it. There's also a 7805 in the middle to provide internal voltage regulation, and two large power resistors for the L298 current sensing. In the pic you can see the L298 screwed to the case at the top for heatsinking, DB9 connectors at the bottom and left for input signals and motor connnections, and the motor protection diodes. The case is Hammond 1590B diecast aluminum. Here's a (terrible) pic taken with my laptop camera, showing the driver unit with the cover removed: In fact, I regularly throw it across the room when teaching electronics classes, to demonstrate how simple designs can also be reliable and rugged. It's about ten years old, and still works like a charm. I was just rummaging through some boxes and found one of my L297/298 stepper motor drivers.
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