Simulation Design Of Fast Transient Response LDO For High Speed Optical Transceiver Chips

In recent years,as 5G communication technology,Io T technology,and the automotive industry continue to develop,various electronic devices are increasingly demanding low dropout linear regulators(low drop-out regulator,LDO).Fast response,low temperature coefficient,low dropout also become its application in high-speed optical transceiver chip to be solved problems.However,traditional LDO circuits cannot meet these requirements.Therefore,improvements have been made to traditional LDO circuits to address these issues.The LDO circuit is composed of a bandgap reference circuit and an LDO circuit.The bandgap reference circuit provides a temperature-independent reference voltage,while the LDO circuit outputs a larger and more stable voltage based on this.In this article,a low-temperature coefficient bandgap reference circuit and a fast transient response LDO circuit were successfully implemented using 0.18μm BCD technology.This article first introduces the basic principles and simulation methods of a bandgap reference circuit,and further analyzes the structure of the proposed bandgap reference circuit.The bandgap reference circuit adopts a compensation circuit structure,using a current mirror and a resistor to control the working state of the PMOS transistor,and using the current generated by the PMOS transistor in different working regions to compensate for the positive temperature coefficient current in the bandgap reference circuit,thereby achieving a bandgap reference circuit with low temperature coefficient characteristics.Second,this paper describes the design process of the LDO circuit,in which PMOS tubes are used as power tubes to achieve low voltage drop.A two-stage operational amplifier is used for the error amplifier,and a transient enhancement circuit is added to detect changes in load current and to speed up the recovery time of transient response.Finally,to verify the performance of the circuit,simulations were performed in Cadence IC617.The simulation results show that the temperature coefficient of the bandgap reference circuit is 2.792 ppm/°C over the temperature range of-24～81 °C.The reference voltage reaches a stable value of 1.2914 V after 1 μs after the circuit starts;the quiescent current of the LDO circuit is 1.9 m A,the differential voltage is 172 m V,and the transient response recovery time is within 1.23 μs,stable output voltage is 2.998 V.Finally,the layout of the LDO circuit was completed and verified by DRC and LVS.