Research And Design On SOI Monollithic Dielectrically-isolated CMOS Analog Switches

CMOS analog switches which are based on SOI technology have many advantages, such as low on-resistance, high speed, no latch-up effect, high integrated density, small parasitic effects, high resistance to radiation. The switches are mainly applied in avionics, ATE industrial control equipment, sampled-data systems and so on.In this article, the SOI dielectrically-isolated CMOS analog switches are four single-pole single-throw channeles, which are designed by SOI CMOS process and use16-pin dual in-line packages. The normal operating temperature range of the chip is from-25℃ to 125℃ and operational power supply is ±15V. Compared with traditional CMOS analog switches, the design uses monolithic dielectrically isolated CMOS, so low on-resistance(64Ω), low leakage current(500pA), CMOS/TTL direct interfacing,and overvoltage protection up to ±25V which is above the power supplies are acquired by using a special circuit design and a monolithic dielectrically isolated CMOS precess.Firstly, the simulation tool TSUPREM4 and MEDICI are used to design and simulate the process and the power MOS devices which are used in the analog switches. So that the process can achieve the design demands by cooperated with the CSMC. Secondly, five modules of the analog switches are designed, whitch includes ESD protection circuit, input circuit, buffer circuit, level shifting circuit, MOS switch circuit. And the substrate bias in the power MOSFET of the MOS switch circuit is floating, which can improve the performance of the circuit. Then whole circuit is simulated by the simulation tool Hspice and the result of simulation achieves the design demands. At last, the simulation tool L-edit is used to design the layout of the circuit. And after taping out the chip, the parameters of the analog switches are tested.The test results show that the relevant design indexes of this chip have been successfully achieved.