With the increasing number of electronic devices with complex functions,CMOS analog switches are widely used in consumer electronic devices such as video switches,bus switching,digital cameras,and notebook computers because of their high performance and low power consumption.In this paper,a high-performance double-pole double-throw analog switch is designed,which solves the problems of large on-resistance,large power supply current,and large parasitic capacitance of traditional analog switches.In order to solve the problems of large on-resistance and high power consumption of traditional analog switches,0.25μm BCD process technology is used,and some high-performance circuits are used to improve traditional analog switches.Firstly,a novel switching structure is adopted,and the technique of keeping Vgs constant is adopted,and then the circuit structure is simulated and adjusted.Secondly,the layout design is completed and post-imitation is carried out,and finally the design is verified by testing.The main research contents are as follows:1.An analog switch is designed,which connects a MOS switch and a T-switch in parallel.It is an n-channel architecture driven by a charge pump.The architecture adopts the double-well process,which combines the advantages of MOS switch and T-switch.It not only reduces the on-resistance value of the analog switch,but also achieves a stable on-resistance within the full swing range of the input signal,and can realize the bidirectional transmission of the analog switch and reduce the influence of the body effect.The structure of the circuit is constructed,and then the performance indicators of the circuit are simulated.2.In order to make the n-structure circuit work efficiently,a low-power oscillator circuit is designed in this paper.It provides a sampling clock for the n-structure,and continuously samples the input signal,so as to realize the constant Vgs of the switch transistor.The oscillator circuit achieves low power consumption through the mechanism that the voltage across the capacitor cannot be abruptly changed and by adding a resistor at key positions.In addition,this paper designs a fault protection circuit for the chip.In order to reduce the power consumption of the whole chip,it does not use the traditional diode or comparator structure,but uses the voltage control characteristics of the MOS switch to design.3.The high-performance analog switch designed in this paper is tested.Firstly,the chip implements the function of a double-pole double-throw switch and overvoltage protection.Secondly,test under the condition that the power supply voltage is 3.0V and the temperature is 25℃.The on-resistance is 5Ω,the on-resistance flatness is 0.1Ω,the supply current is as low as 0.87μA,the turn-off isolation is-65d B,the crosstalk is-80d B,the turn-on time is 2.6μs and turn-off time is 736ns.The entire chip area is 0.65mm~2.Compared with the traditional analog switch,the high-performance analog switch designed in this paper has lower on-resistance value,better linearity and lower supply current. |