Ldo Linear Step-down Converter

The power management IC (integrated circuit) has the many advantages, such as high integrity, high price ratio, the most simple outer circle circuit, the best capability, the high-efficiency power supply etc. So, it has the vast market foreground. The circuit designed in this paper uses for those system: digital signal processor (DSP), ultra low power microcontroller, and any other low power processor. The general application includes the PDA, MP3, DC, radiotelephony and the network of database, instrument etc. At present, many aboard companies still mostly occupy the market of power management IC. It has important significance to research and development of domestic power management IC. And it has much great importance to require such a big market. Therefore, it is of great importance to study the LDO linear regulator circuit. The object of this paper is to design a low dropout voltage (LDO) linear buck regulator. It adopt 0.6 um CMOS technology , which has the wide input voltage range( 2.5V-5V). The output voltage is 1.8 V. When the load current is 800 mA, the dropout voltage is only 217 mV. This circuit is primarily used to power supply of the circuit such as CPU, DSP etc. In addition, it also designs the thermal shutdown and current limit sub-block, which guarantee the electric circuit working in safe operation area(SOA).At the same time, the Error flag function can generate a signal that presents the power supply status of the behind circuits.During circuit designing, the basic theory of LDO linear buck regulator is given first. Then the general structure of the IC is designed based on its function requirement. And then designs the sub-block circuits in details. Applying Cadence and Hspice, simulations of the sub-block circuits and whole chip, and giving the reasonable electric circuit data. The results indicate that the IC has achieved their function object and numeric object.