Design of Low Drop Out Regulator with High Robustness ESD Protection Circuit Using Current Buffer Structure

Abstract

This paper proposes an LDO regulator that uses a current buffer for the peak voltage exposed to the load current. In the case of conventional LDO regulators, a method of adjusting the size of the external capacitor has been used to alleviate overshoot and undershoot phenomena. When the size of the external capacitor increases, the overshoot and undershoot voltages are reduced, but the chip size increases. Therefore, the proposed LDO regulator is designed to have improved overshoot and undershoot voltages using the current buffer structure instead of the method of resizing the external capacitor. The current buffer structure was designed so that it could detect the overshoot and undershoot voltages generated from the feedback voltage, and charge and discharge the current. As a result, it was verified that the LDO regulator with the current buffer structure could improve the overshoot and undershoot voltages according to the load current. The LDO regulator having the current buffer structure has a load current of up to 250 mA at the output voltage. According to the measurement results, when the load current is 250 mA, the power voltage according to the undershoot is 38 mV, and the power voltage according to the overshoot is 29 mV. Additionally, the LDO regulator with a current buffer structure has an ESD protection circuit built in to ensure reliability in ESD situations.