Research And Design Of A High Current, High Stability Of The Ldo Linear Regulator

Recently, with the deterioration of the energy crisis, as well as the popularization of the portable equipments like cellphone, handbook computer, people give more and more requirement to power management ICs. As a common-used power management IC, LDO (low dropout voltage regulator) receives more and more attention. LDO is a DC/DC regulator which has the ability of certain output current, compared with DC/DC switch regulator and charge pump, LDO has the advantage of small ripple and noise, low EMI, fast transient response, and requires few external components. These advantages make LDO the"cosset"in the industry circles, remaining the top in the proportion of the whole power management IC market during these years[1]. Large output current is one of the trend of LDO, but large output current makes the system unstable easily and is the key point of the LDO's design. Therefore, the study of large output current, high stability LDO has certain meaning in both theory and practice.In this background, an LDO circuit which has the ability of large output current (1.3A) is proposed in this paper. This circuit has an output voltage of 2.5V, and its input voltage ranges from 2.4V~5.0V, when the output current reach the highest level (1.3A), its dropout voltage is 0.5V. The loop of this circuit is compensated by a novel load-tracking method, hence has relatively high stablility. In order to accelerate the speed of the transient response, a transient response enhancement circuit is added. Besides, the over-temperature protection module and over-current protection module can prevent the circuit from the damage of too high temperature or too heavy load.The LDO circuit proposed in this paper is designed with the 0.5um standard COMS process. Paper introduces the working theory and the basic index of the LDO first, and analyse its loop stability in particular. Then, the disavatage of the traditional RESR zero compensation is pointed out, and the working theory of the novel compensation method proposed in this paper is expatiated, with the Hsipce simulation evidence in followed. Subsequently, combined with the the integer function, the analysis and simulation of the transient response enhancement module, the over-temperature protection module and over-current protection module is finished. Finally the analysis and simulation of the whole circuit is given.