An Ultrasonic Transducer Interface IC With Integrated Push-Pull 40 Vpp, 400 mA Current Output, 8-bit DAC and Integrated HV Multiplexer

We present an ultrasonic transducer interface IC that includes an 8-bit, 40 V_pp, 400 mA current output DAC for arbitrary waveform transducer excitation and a ±25 V analog multiplexer. The IC was fabricated using a 0.35 μm, 50 V CMOS process. The design eliminates the need for an external power amplifier as the piezoelectric transducer is driven directly from a segmented push-pull current output DAC, which simplifies the overall system design. This approach has the advantage of simple and rapid glitch-free power-up/down, which is especially important in integrated high-output-power drivers. The DAC has been evaluated when operating at a 150 MHz sampling rate with a ±400 mA output current and a 50 Ω load. Measured performance includes 37 dB SNDR and 46 dB SFDR at 10 MHz output frequency. By implementing an additional reference DAC and extending the receiver isolation switch into an analog multiplexer, we enable on-line calibration for the purpose of reducing the driver and receiver signal path uncertainty. Measurements show a greater than ten-fold improvement in delay uncertainty to approximately 20 ps for temperature variations of 0 to 70 degrees Celsius.