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where TJ(max) is the maximum allowable junction tempera- ture of the die, which is 1250C, and TA is the ambient operat ing temperature. ejA is dependent on the surrounding PC board layout and can be empirically obtained. While the OJC (junction-to-case) of the SOT23-5 package is specified at 1300C /W, the OJA of the minimum PWB footprint will be at least 2350C /W. This can be improved by providing a heat sink of surrounding copper ground on the PWB. Depending on the size of the copper area, the resulting OJA can range from approximately 1800C IW for one square inch to nearly 1300C IW for 4 square inches. The addition of backside cop per with through-holes, stiffeners, and other enhancements can also aid in reducing thermal resistance. The heat contrib uted by the dissipation of other devices located nearby must be included in the design considerations. Once the limiting parameters in these two relationships have been determined, the design can be modified to ensure that the device remams within specified operating conditions. If overload conditions are not considered, it is possible for the device to enter a thermal cycling loop, in which the circuit enters a shutdown condition, cools, re-enables, and then again overheats and shuts down repeatedly due to an unmanaged fault condition.