DRV595: Getting very hot

Part Number: DRV595

I am using the DRV595 to drive a 7V, 1A TEC and I have an overheating issue on a new project. The conditions are:

1. Power supply voltage of 7V

2. Ambient is 25C

3. Max TEC current is 1.1A (full drive)

4. According to those figures I should be dissipating only 0.13W across the two internal output transistors 1.1A x 1.1A x 60mOhms x 2

5. In theory, this gives me a temperature rise of only 3.3 degC above ambient

6. The layout of the PCB is according to the data sheet with thermal pad and thermal vias.

7. The switching frequency is set to 1MHz
8. The device works until it gets hotter (when fully driving the TEC) until it goes into the fault condition.

The symptoms are:

1. The DRV595 is going into FAULTZ condition and turning off the output

2. The temperature measured on the top of the package of the DRV595 is in excess of 60degC

Any ideas what is happening here or have I just got the math totally wrong!