TL2575-05I Heat, noise and wrong output

Hi,

I'm troubleshooting a circuit built by a fellow electrician. I traced the problem back to TL2575. Already at a 12V input voltage, the IC is getting really noisy and extremely hot. On the other hand, it is only delivering 3.4V instead of the promised 5V. I checked the circuitry and it is exactly as recommended in the datasheet. Can anyone guess what could be wrong?

Thanks in advance