Design and implementation of ASIC for portable piezoelectric ultrasonic arrays

Abstract

Ultrasonic detection and imaging are well known techniques in medical diagnosis and industrial applications. They are based on the principle of pulse to echo detection and are widely applied to medical imaging, range finding, sonars, fingerprinting, proximity sensors and flow meters, among many other applications. In the past decade ultrasound became an interested topic for portable applications mostly due to improvements in transducer fabrication and the introduction of micromachined devices (MEMS). New scaled arrays of micromachined transducers have allowed high-frequency drives and enabled die-level integration of MEMS device with application specific integrated circuits (ASICs). The combination of both platforms facilitates portability but requires a detailed revision of system specification with a focus on reduction of power consumption and frontend area. This work presents the design and implementation of an ASIC interface for portable ultrasonic applications with focus on power-efficient, adaptive piezoelectric micromachined ultrasonic transduces (pMUT) arrays. The proposed ASIC consists of an energy-efficient Analog Front-End (AFE) with 8 high-gain input stages feeding 8 pMUT channels, It also consists of a Time Gain Compensation amplifier, low-power, Charge- Recyclable (Ch-R) high-voltage transmitter drivers, and high-voltage CMOS switches. The ASIC Digital Back End (DBE) implements an ultrasonic pulse-to-echo mode, a mediaadaptive, eight-channel scalable beamformer for beam steering and beam forming. A unique feature of the ASIC interface is the first ever on-chip implementation of an aberration compensation function. The system has been implemented and fabricated using Global foundries 65nm process and consumes a total energy of 2.34uJ/scan using a 4-ch, 500pF pMUT array. The measurement results of the implemented interface circuit illustrate the correct functionality of each of the building blocks, including the aberration compensation circuitry, the beamforming unit and the low-power AFE. This work has been conducted under the MEMS TwinLab Program with GLOBALFOUNDRIES and the Institute of Microelectronics, Singapore.

Date of Award	May 2017
Original language	American English