Low overshoot, low dropout voltage regulator with level detector

Abstract

An ultra-small, low power, low dropout (LDO) voltage regulator is presented which tracks the output voltage with threshold voltages of the underlying process technology. The topology of the regulator is extremely simple because it does not use an error amplifier. Instead a common-gate stage feedback loop is used, reducing the number of active transistors to only 10. This results in extremely small chip area as well as very low power consumption. This regulator is suitable for various applications where high precision of the output voltage is not required, such as controlling the interfaces of the various sub-circuits in highly complex system-on chip designs. Moreover, in many applications, the voltage overshoot from the output of the LDO can cause violations of breakdown voltage limitations on transistor terminals in subsequent stages, and thus damages those transistors. Therefore in the second part of this paper, an improved ultra-small regulator circuit will be discussed with reduced output voltage overshoot for sharp input voltage ramps. It also comprises a simple, new level detector circuit which indicates if the regulator is in regulation mode or passive mode.