| With the rapid development of the domestic electronics industry,the upgrading of electronic products is becoming faster and faster,accompanied by the increasing market demand for power management chips.Low Dropout Regulator(LDO)has become the most widely used chip type in power management chips because of its simple structure,fast response,small output ripple and other outstanding advantages.The small size and easy integration of LDO also make it more common to use in today’s increasingly high chip integration environment,and the LDO has been widely integrated into a variety of chips as modules.In order to reduce output pins,the design of LDO without external capacitor has gradually become a research hotspot.However,the transient response characteristics of LDO after removing the external capacitor will become very poor,which is also the focus and difficulty of this design.In order to deeply study the transient response characteristics of a capacitor-less LDO,a LDO circuit structure is designed in this thesis.The circuit is designed by Cadence software using based on Global Foundries 180 nm technology.The main structure of the LDO includes error amplifier,bandgap reference circuit,over-temperature protection circuit,under-voltage protection circuit and over-current protection circuit.Capacitor-less LDO will have defects such as slow speed,poor stability and large output voltage error when responding to load transient due to its lack of external capacitance.Therefore,in order to stabilize the circuit,a two-stage drive structure and compensation structure are added in the LDO circuit,and a new second-order compensated bandgap reference circuit structure is proposed to output a more stable reference voltage.In order to solve the problem of slow response speed,a fast charging and discharging feedback path is specially designed for the LDO circuit.The input voltage of the designed LDO circuit in this thesis is 2 V ～ 5 V,the output voltage is 1.8 V,and the maximum output load current is 100 m A.The simulation analysis shows that the static power consumption of the LDO is about 150μA,the load adjustment rate is 1.67%,and the linear adjustment rate is 0.04%.The overshoot and undershoot voltage during the transient change of load current are 153 m V and 109 m V respectively,and the recovery time is less than 2 us.Compared to ordinary LDO circuits,the designed LDO has shorter recovery time and smaller overshoot and undershoot voltages,meeting the need for fast transient response. |
