A transient-improved low-dropout regulator with nested flipped voltage follower structure

SUMMARY

In this article, the existing low-dropout regulator (LDO) based on cascoded flipped voltage follower (CAFVF) is reviewed. A new method to simulate the open-loop gain of an LDO with a CAFVF structure is conveyed. The drawback of CAFVF-based LDO is that the nondominant pole locates at low-frequency and pole-zero cancellation using a large equivalent series resistance of loading capacitor is required for stability. To tackle this problem, a novel LDO structure based on a nested CAFVF is proposed and analyzed in this article. It is shown that the nondominant pole is pushed to a high frequency and the LDO stability is improved. The proposed circuit is fabricated using a commercial 0.35-µm CMOS technology, and the load-transient response between 0.5 and 60 mA settles at approximately 5 µs. Copyright © 2012 John Wiley & Sons, Ltd.

In this article, the existing LDO based on CAFVF is reviewed. A new method to simulate the open-loop gain of an LDO with a CAFVF structure is conveyed. The drawback of CAFVF-based LDO is that the nondominant pole locates at a low-frequency and the pole-zero cancellation using a large equivalent series resistance of loading capacitor is required for stability. To tackle this problem, a novel LDO structure based on a nested CAFVF is proposed and analyzed in this article. It is shown that the nondominant pole is pushed to a high frequency and the LDO stability is improved. The proposed circuit is fabricated using a commercial 0.35-µm CMOS technology, and the load-transient response between 0.5 and 60 mA settles at approximately 5 µs.