A Novel Fold-Back Current Limiting Protection used in Sub-threshold LDO for Wireless Sensor Applications

This paper presents a novel fold-back current limiting protection circuit used in sub-threshold low dropout regulator (LDO) for wireless sensor applications. By sensing the output current and output voltage, then comparing the sampled results with VREF, the proposed protection circuit can control the gate voltage of the power transistor to limit the output current. The maximum output current and short current of the sub-threshold LDO can be limited to 330 mA and 90 mA, respectively, which can save up to 71.9% of power consumption in the case of an output short-circuit condition compared with traditional constant current limiting protection methods. In a 0.35-μm CMOS technology, the sub-threshold LDO can provide a 3.3 V output voltage stably under the 5 V input voltage when the load current changes from 1 μA to 200 mA, and the load regulation rate is only 0.019 mV/mA.