Design of a foldback current limit circuit in LDO

In order to prevent the chip from being damaged by excessive load current or short circuit, a foldback overcurrent protection circuit for LDO is introduced. Through the accurate sampling of the power tube, according to the size of the load current, the fixed current limiting loop and the short circuit current limiting loop are switched to achieve the purpose of over-current protection. Without increasing the output short-circuit current, the turning point of the output current is adjusted to avoid the intersection of the over-current curve and the load curve, so as to prevent latch-up. Based on 0.35μm CMOS process, Hspice simulation is used to verify that the maximum output current and short-circuit current of the over-current protection circuit are limited to 700 mA and 20 mA, respectively. The over-current protection function is well realized, and the short-circuit power consumption of the system is reduced.