Design of Low Drop Out Regulator with ESD Protection Structure Using Push-Pull Detection Circuit For Power Conversion

Abstract

In this paper, a capacitor-less LDO using a push-pull detection circuit for power conversion is presented. The push-pull detection structure is proposed to mitigate the overshoot and the undershoot phenomena caused by the removal of the existing external output capacitor. Conventional LDO regulators suffer from overshoot and undershoot, which are caused by imbalances in the power supply voltage. Therefore, the proposed LDO was designed to have a more improved transient response to form a new control path while only keeping the feedback path of the conventional LDO. A new control path detects the overshoot and the undershoot phenomena occurring on the output-stage. Therefore, the operating speed of the pass device is improved by charging and discharging the current of the gate node of the pass device. As a result, the proposed LDO was confirmed to improve the transient response and regulation characteristics. Further, the area was successfully reduced by removing the external capacitor. The proposed LDO regulator was designed by adding a push-pull detection circuit between the output terminals and between the gate terminal of the pass transistor and the output terminal of the error amplifier installed in the conventional LDO regulator. The LDO regulator with a push-pull detection circuit operates over an input voltage range from 3.3 to 4.5V and has a load current of up to 200mA at an output voltage of 3V. According to the measurement results, when the load current is 200mA, the voltage is 22mV under the undershoot condition and 19mV under the overshoot condition. Lastly, ESD robustness characteristics of HBM 8kV or higher have also been secured.