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A 0.18 μm 1.5 V/50 mA stability-enhanced low dropout regulator (LDO) is presented. A multi-path error amplifier and a split pass device structure are utilized for pole-zero pair compensation. The proposed LDO can be stable without a load capacitor and also stable with different combinations of load capacitors and equivalent series resistance.

In this paper, a new compensation scheme and a corre-sponding pass element structure for a CMOS low-dropout regulator (LDO) are presented. The proposed approach effectively alleviates the strict stability constraint on the ESR of the output capacitor. Stability of a CMOS LDO with the conventional compensation requires the effective series resistance (ESR) of the output capacitor in a tunnel-like region. With the proposed design approach, an LDO can be stable using an output capacitor without ESR. A 2.5V/150mA LDO has been implemented using a 0.5-μm 1P2M CMOS process. The experimental results illustrate that the proposed LDO is stable with an output capacitor of 0.33μF and no ESR.