STR711FR1T6 device is available on (TQFP 64 - 10 x 10 mm / 0.5 mm pitch) - TA is the Ambient Temperature in °C = (-40 to +85 °C) - JA is the Package Junction-to-Ambient Thermal Resistance, in °C/W = (45 °C/W ), to get more information about how this value was calculated please refer to section (3.2 Thermal caracteristics) STR71x datasheet Rev.7. regards, Hich ;)