Low voltage current limit loop

摘要

A current limit circuit is provided which may be used to limit the current conducted by a pass transistor in a low dropout voltage regulator circuit having no ground terminal. The output current of the regulator is sensed by a low value resistor in the collector of the transistor. The voltage developed across the resistor is proportional to the output current of the regulator, and is used to vary a current ratio which sets the current limit value. The gain of the current limit loop is increased by providing positive feedback during current limiting. A foldback network is provided which reduces the current limit value at higher input/output voltage differentials. The feedback provided by the foldback network has a breakpoint which is sensitive to the operating temperature of the regulator circuit.