High-precision, Low Noise Ldo Linear Regulator's Design

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 demand. This paper aims to the application that requires high accuracy and low noise. Under this context a high accuracy and low noise LDO (low dropout regulator) is designed.In the LDO, reference is a critical circuitry that it determines the accuracy. Using Curvature-Compensation, the temperature coefficient is greatly improved, from about 20ppm/℃to 0.5ppm/℃.A preregulator help to higher the PSRR (power supply rejection ratio) and a 500nF off-chip capacitor bypasses most of the reference's output referred noise.This paper takes advantage of the 0.5μm BiCMOS process that the bipolar transistor has lower flicker noise than their MOS counterparts, so bipolar transistor is used to form the critical node of the error amplifier. To make sure the stability and lower the transient overshoot of the LDO, a buffer stage is used to isolate the pass element and the output of the error amplifier. The output resistance of the buffer is reduced by a negative feedback. And the buffer is dynamically biased to reduce quiescent current of the LDO. Two zeros are introduced near the non-dominate poles as the frequency compensation.This paper first shows the prospective market demand of power management IC, then it introduce the specifications of the LDO. In the next, some relative analyze is performed and noise analyze is performed. After this, a reference is designed and then the other parts of the LDO. Simulation is performed under the Cadence Spectre environment, and the results show that all specifications are achieved.