A New LDO Regulator with Adaptive PSR Improvement Under Wide Load Current Range and Fast Load Transient Response

This paper presents a novel off-chip capacitor-less LDO with high PSR from $40\mu \mathrm{A}$ to 45mA load current range. Changing the load current in conventional LDOs causes a variation in the output resistance of the LDO and moves the pole located at the pass transistor's gate terminal. These changes result in the PSR degradation at some load current ranges, in such a way the LDO cannot satisfy the required PSR at the whole load current range. The proposed LDO provides an adaptive feed-forward path to improve the PSR at the entire load current ranges. The transfer function of the proposed feed-forward path has a zero with a specific gain, that is skillfully shifted by the amount of output resistance and the pole positioned at the gate terminal of the pass transistor. This method leads to enhancing PSR across the entire load current spectrum. According to simulation findings for the suggested LDO in TSMC 180 nm CMOS technology, the output PSR reaches −60 dB at 13 kHz across the entire load current range. The proposed LDO operates without requiring an external off-chip capacitor, exhibiting a quiescent current of 900nA and a phase margin of 54 degrees within an input voltage range of 1.8 to 2.3 volts.