The Research And Design Of Low-Power High-Stability LDO

As the development of electronic productions, power management technology is widely applied to different kinds of electric system. As a familiar part of power managements, the low drop-out (LDO) linear regulator has the characteristic of high regulation, low ripple and low output noise, and is widely applied in cell phone, audio devices, bluetooth, wireless LAN, handheld organizers, and PDAs. As the increase of the circuit integration and the portable products,, the low drop-out linear regulator will be available in large loads, low power dissipation, high efficiency and high stability applications.The topology of the system and the key technologies of the system are researched and analyzed in this dissertation firstly. In order to perfect the function of the system, some functional modules are introduced to enable and protect the system, which include under voltage lock-out, current limiting module, over temperature protection, low pass filter for bandgap voltage, quick start module and so on.Then, the circuit level design of the modules is introduced detailedly. Based on the comparison and analysis of advantages and disadvantages of some basic blocks, this dissertation gives the improvements, and proposes the proper structures for the chip. The key modules mainly contain error amplifier, bandgap voltage reference, current limiting circuit, over temperature protection, the transient response help circuit and the system stability compensation circuit.The system is designed in 1.5μm BCD (Bipolar-CMOS-DMOS) technology, and simulated by the SpectreS of Cadence Company. The simulation results show that the system current is about 69μA, the power supply rejection (PSR) is about 53dB, the drop-out voltage is about 200mV while the load current is 200mA, and the system could operate stably from light load to heavy load when the load capacitor is 2.2μF. It is obvious that the designed LDO linear regulator doesn't only have the characteristics of low power, high PSR, low output noise, but also has quick start-up, high regulation, low drop-out voltage and high stability. And all simulation results of the low drop-out linear regulator are consistent with the expectations and the system performance is well.