Design And Research Of Bipolar LDO Linear Regulator XD1622 With 1A Load Current

The popularization and rapid growth of portable electronic products result in that more and more attention is now paid to power manage projects with the high performance and low cost. As a competitive kind of power management, the new generation of low dropout (LDO) linear regulator with ultra low noise, high PSRR, micropower loss and the lowest cost will be holding an important position.The object of this paper is to design a bipolar low dropout (LDO) linear regulator XD1622, which adopts EPISIL 5μm BJT technology. The input voltage range is as wide as from 13V to 29V, while the output is constant at 12V. The dropout voltage and quiescent current is only 280mV and 4.6mA respectively in 1A typical load current. A low-power, high reliability current limit circuit is proposed, which can effectively lower the power dissipation of the circuit. The circuit can reduce the power dissipation by 25% compared with the conventional constant current limit and enhance the reliability of the system with the application of fold back function. In addition, the thermal protection and safe operation area (SOA) protection of pass transistor are designed, which guarantee the electric circuit working in safe operation area (SOA).Firstly, the operational principle of the LDO linear regulator XD1622 is analyzed, based on which the systematic architecture of the whole chip is constructed and the specifications are given. According to the specifications, the internal modules of the chip are designed in detail including the bandgap voltage reference, the error amplifier, the thermal protection, the over-current protection and the enable circuit, etc. The type of the pass transistor is chose after comparing the characteristics of several kinds of transistors. And then the design of the sub-block circuits and the simulations using Hspice are presented in detail. Meanwhile, the parameters of the ciucuits are determined. The results show that the electric specifications of the sub-circuits all meet the prospective specifications. At last the simulations of the whole chip are presented and the simulation results indicate that the IC has realized its function and meet the prospective specifications.