![]() Imagine something like a 3.5" hard drive falling from the table on your leg every second. But switching converters are a lot more complex and harder to do right on the first time, so if you can tolerate the few watts of heat being produced in your circuit and have means of getting it out of the enclosure like fans, ventilation holes, metal case, etc., consider just using a proper heatsink.Īlso, the figure 2W doesn´t seem as large, but imagine that it is equivalent to the power produced by a 0.2kg weight falling from 1m every second. This means that at 2W without any heatsink, the die of the device will be at a whopping 155☌ if your ambient temperature is 25☌, and the case will be 10☌ less, but 145☌ is still a nice way to burn your fingers.Īlso, the device has maximum junction temperature of 125☌, so you really should either get some reasonably large heatsink, or use a switching converter. Changes in VO due to heating effects must be taken into account separately. ![]() Load and line regulation are specified at constant junction temperature. The fairchild datasheet says that the thermal resistance junction-case is 5K/W and junction-ambient is 65K/W. Fixed output voltage of 5V 500mA output current Dropout voltage of 2V Maximum input voltage of 35V No external components required Operating junction. Electrical Characteristics (LM7805) Refer to the test circuit, -40☌ < TJ < 125☌, IO 500 mA, VI 10 V, CI 0.1 F, unless otherwise specified. You are dropping 4V between input and output, and at 0.5A that makes 2W, and that is a LOT of heat without a heatsink. ![]()
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