Miniaturizing Ultrasonic System for Portable Health Care and Fitness

We present a miniaturized portable ultrasonic imager that uses a custom ASIC and a piezoelectric transducer array to transmit and capture 2-D sonographs. The ASIC, fabricated in 0.18 $\mu$ m 32 V CMOS process, contains 7 identical channels, each with high-voltage level-shifters, high-voltage DC-DC converters, digital TX beamformer, and RX front-end. The chip is powered by a single 1.8 V supply and generates 5 V and 32 V internally using on-chip charge pumps with an efficiency of 33% to provide 32 V pulses for driving a bulk piezoelectric transducer array. The assembled prototype can operate up to 40 MHz, with beamformer delay resolution of 5 ns, and has a measured sensitivity of 225 nV/Pa , minimum detectable signal of 622 Pa assuming 12 dB SNR ( $4\sigma$ larger than the noise level), and data acquisition time of 21.3 ms. The system can image human tissue as deep as 5 cm while consuming less than 16.5 $\mu$ J per pulse-echo measurement. The high energy efficiency of the imager can enable a number of consumer applications.