CMOS design of a capacitively isolated AC switch driver for auto-turning frequency

Abstract

Abstract Cancer is one of the leading causes of death worldwide. Benefiting from technological advances, new approaches for treatment are being proposed, studied and tested. High intensity focused ultrasounds (HIFU) is one of them. To further improve the performance of such a system, using integrated driver to ultrasound transducers is one step forward. To reach this goal, several design challenges must be overcome: the driver design must be compatible with complementry metal oxide semiconductor (CMOS) technology; it also must be compatible with magnetic resonance imaging (MRI) equipment used for treatment monitoring; and it should be immune to the floating ground necessary for AC-switch implementation for some specific implementation. In this article, a new AC-switch driver used within a HIFU system for a resonant circuit autotuning is proposed. A capacitive isolation is chosen so that the designed driver is compatible with both CMOS technology and MRI. It is designed in a CMOS HV 0.35 μm. The simulation results have shown that with just a 10 ns delay, or 1% of the control signal cycle, this system may run with a floating ground that can reach 180 Vpp with respect to the main ground, leading to a relative inaccuracy of 0.065% of the resonance frequency of the tank circuit. The design is well balanced so that it minimizes the carrier frequency, power consumption, and created signal latency. By using the proposed active biasing circuit, the system’s power usage is further cut in half while still maintaining a floating ground voltage of 160 Vpp, which is sufficient for our needs.