I'm designing a new PCB using the Automotive grade ATmega64M1 chip in the 7mmX7mm QFN32 package. It has a large solder pad on the bottom.
Nowhere in the datasheet can I find where I'm supposed to connect this pad to ground. It seems like every other QFN device specifically calls this out.
Also, which ground should be connected? Digital ground (GND) or analog ground (AGND)? Or should I tie them together under the package?
Since I'm not suspecting that the microcontroller is going to generate much heat at all, can I omit the thermal feed-throughs to the bottom side of the PCB?
This device is going to go into a pretty harsh environment as far as temperature extremes, pressure and vibration, so I'd like to think that I'm doing everything I can to bolt the chip down properly to the PCB. Any other harsh environment design tips would also be appreciated.