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LDO FAQs Slide 4

What is the difference between thermal limiting and thermal shutdown? With thermal shutdown, the part is actually shut off and the die must cool down by the amount of hysteresis built into the thermal shutdown circuitry. Once the part has cooled down, the part is restarted. If the fault or overload exists, the part heats back up to the thermal shutdown temperature and turns back off. Therefore, the part sits and thermally oscillates at some low frequency and duty cycle depending on the thermal shutdown temperature, the amount of hysteresis, the package and the associated thermal time constants. Linear Technology's higher current (i.e. ≥500mA) LDOs generally utilize this type of protection. Thermal limiting is a slightly less sophisticated technique than thermal shutdown, in which the maximum die temperature is controlled by the protection circuit limiting the power dissipation on the die. Linear Technology's lower current LDOs generally have this protection.

PTM Published on: 2011-05-16