An 8 Channel Transceiver ASIC to Interface a CMUT Array

Abstract

This paper presents an 8 channel interface ASIC for a 2D Capacitive Micromachined Ultrasonic Transducer (CMUT) array. We propose a novel interfacing scheme to eliminate the need for a high voltage (HV) external DC biasing. A two-level HV driver circuit switches between two HV levels to produce a 47 V peak to peak output pulse with rise and fall times of 78 ns and 67 ns at 1.8 MHz. A resistive feedback transimpedance amplifier (TIA) with 4 adjustable gain settings that converts a time-varying current input into an output voltage is used in the receive path. The TIA has a measured −3 dB bandwidth of 4 MHz at the gain setting employing a 300 kΩ resistor in the feedback network. The input referred noise current is measured to be $2.6{\text{pA}}/\sqrt {Hz} $. A pulse-echo measurement on a CMUT sample demonstrates successful transmit-receive operation of the system. The chip is fabricated in a 0.18 µm HV SOI CMOS process with an active area of 6 mm2.