We are using LTC3637 to generate +12v to -12v as per the typical application diagram given in datasheet pg no 21.
Usually we will connect EXPOSED PAD of IC to ground, but in our case output(-12v), is taken from the ground pin. According to datasheet pg no 8, exposed pad (pin no 17) is connected with gnd (pin no 8) so we have to connect exposed pad also to output(-12v).
Our concern is, if IC will be able to withstand the thermal extremes or not , since exposed pad cannot be grounded and is to be connected to -12V?
Yes, you still need to connect exposed pad to chip GND, which is -12V in this case. The thermal should be fine. You can measure the temperatures on your board based on your test conditions. Thanks.