Design And Realization Of A High-performance Analog Switch

Recently,analog integrated circuits have been developing rapidly.Analog switches have been extended to many fields,such as medical equipment,audio players,high-speed storage interfaces,etc.Analog switches are often used not only in the field of life,but also in the military,aerospace and aviation fields.Analog switches are popular with the public for their easy integration and strong functions.The analog switch is to control the on and off of the signal,and the pursuit of the signal transmission is perfect,which requires the performance of the analog switch to be good.When designing it,it is necessary to consider the signal transmission frequency of the analog switch and adapt to high-speed signal transmission.But it also need to consider the matching degree between signal channels,reduce the on-resistance,improve the linearity of signal transmission,increase isolation and crosstalk,etc.Therefore,improving the signal transmission capability is critical for analog switches.(1)The circuit designed in this article is mainly aimed at completing the research of a high-performance analog switch in terms of speed,signal transmission range,signal transmission linearity,on-resistance,etc.Firstly,the working principle and performance indicators of analog switches are analyzed.The structure of traditional charge pumps are analyzed.A charge pump structure that can reduce on-resistance and fast power-on is proposed.The charge pump structure is used to control the turn-on of the switch MOS transistor.The dynamic comparator structure is adopted to enhance the signal transmission capability.The parameters such as isolation,distortion rate,insertion loss and on-resistance of the transmission signal of the circuit are studied.It explains the working process of the circuit in detail,and points out how to realize the function and performance of the circuit.By optimizing the design of the circuit,the circuit can meet the design goals.(2)This design passed the software simulation to make the performance reach the design index,and then processed the chip in the factory,drawn the PCB board,placed the chip on the PCB board,and tested the chip for verification.The circuit adopts0.18μm CMOS technology,and designed a double-pole double-throw analog switch circuit with low on-resistance,high bandwidth,low power consumption,negative signal transmission,low leakage current,and overvoltage protection capability.The main circuits include an oscillator,a frequency divider,a charge pump,a output voltage circuit that changes in positive correlation with power supply voltage,and an overvoltage protection circuit,etc.(3)Through software simulation,the-3d B bandwidth of the analog switch is10.53 GHz,the isolation is 106.1d B,the crosstalk is 105.1d B,and the distortion rate plus noise is 0.0015%,and the leakage current is less than 25 n A.The overall circuit has been tested,it shows that the power supply current is less than 20μA,the on-resistance is about 3.8Ω,which has good signal transmission capabilities.The signal transmission range is-2.3V to 5V,and the resistance flatness is 0.3Ω.In addition,the circuit’s turn-on time is 5.4μs,and the circuit’s turn-off time is 4.0μs.The overvoltage protection capability is within the expected index.The overall chip area is970μm×695μm.