A Front-End ASIC With High-Voltage Transmit Switching and Receive Digitization for 3-D Forward-Looking Intravascular Ultrasound Imaging

Abstract

This paper presents an area- and power-efficient application-specified integrated circuit (ASIC) for 3-D forward-looking intravascular ultrasound imaging. The ASIC is intended to be mounted at the tip of a catheter, and has a circular active area with a diameter of 1.5 mm on the top of which a 2-D array of piezoelectric transducer elements is integrated. It requires only four micro-coaxial cables to interface 64 receive (RX) elements and 16 transmit (TX) elements with an imaging system. To do so, it routes high-voltage (HV) pulses generated by the system to selected TX elements using compact HV switch circuits, digitizes the resulting echo signal received by a selected RX element locally, and employs an energy-efficient load-modulation datalink to return the digitized echo signal to the system in a robust manner. A multi-functional command line provides the required sampling clock, configuration data, and supply voltage for the HV switches. The ASIC has been realized in a 0.18- $\mu \text{m}$ HV CMOS technology and consumes only 9.1 mW. Electrical measurements show 28-V HV switching and RX digitization with a 16-MHz bandwidth and 53-dB dynamic range. Acoustical measurements demonstrate successful pulse transmission and reception. Finally, a 3-D ultrasound image of a three-needle phantom is generated to demonstrate the imaging capability.