Low Dropout Regulator ASIC For Capacitive Micro-machined Accelerometer

Based on analyzing the structure, principle and the parameters of low dropout regulator (LDO) and requirements for the application of micro-accelerometers, the design, simulation and optimization of the important blocks and overall circuit of LDO are presented in this thesis. Important blocks include the error amplifier, bandgap references and PMOS pass element,and the noise performance, transient response, power supply rejection and stability et al of LDO system are mainly analyzed and simulated.Reducing the noise of the error amplifier is the key to reduce the noise of LDO system, and using the chopper stabilization technique can effectively reduce the low frequency noise of error amplifier thus attaining the purpose of optimization the noise of LDO overall system. A high-order curvature compensation technique effectively serves to reduce temperature coefficient of bandgap reference voltage circuit improving its performance to a large extent, and by pre-regulating the supply voltage of core and op amp of bandgap reference, the supply rejection can be enhanced further. Considering the dropout, power consumption and technical conditions, the size of pass transistor is tradeoff between the dropout, output current and stability of LDO system.Without increasing the power consumption and guaranteeing the stability of system, using the current feedback amplifier as the second stage can minimum the effect of slew rate of error amplifier on the transient response of LDO system thus improving the speed of transient response of system. In design, having an additional voltage stage to keep the the gate voltage of pass transistor track with the power supply can improve PSRR. In the end, we have integrated the important blocks that is error amplifier, bandgap and PMOS pass transistor with the other blocks of the LDO and simulation is carried out by Hspice. The simulation results show that the LDO system can keep stability in the load current range from 0~30mA. The loop gain is 74~108dB. The phase margin is above 60°. The input referred noise is 22nV/Hz1/2. The line regulation is 1.133mV/V. The load regulation is 1.17mV/mA. The PSR is 58dB at the frequency of 10kHz. The relevant performance of LDO system can satisfy the application requirement of micro-accelerometer.