TABLE OF CONTENTS The ambient temperature and dissipated power used in the calculations for stress balancing are manufacturer-specified, and have the manufacturers' intended margins. The derated value of power dissipation also has these margins. It may be prudent to add additional margin (P M) in calculating the application power P App to compensate for inaccuracies in thermal modeling, value of ? JA and actual ambient temperature near the device in the application. The device electrical parameters, which are calculated from the derated value of power dissipation, should also be subject to derating. This is to accommodate the errors inherent in the process; however, adequate precautions need to be taken while using this process.
If a parametric pass/fail test is used to test the devices after stress balancing analysis, the test should be carried out at the target application temperature plus an appropriate thermal margin. This will ensure that some margins exist at the target application temperature.
Although stress balancing appears to be straightforward, there are certain hidden difficulties. Data sheet junction temperature limits should be used with extreme caution for calculations in stress balancing, because they do not reflect the maximum junction temperature at which the device would operate. Thermal resistance values of a device are application dependent. If they are used to construct the Iso-T J curve, thermal validation by test or analysis should also be done.
The power dissipated by the device is the power that is lost...
