Jung Gwangrok, Pirouz Amirabbas, Tekes Coskun, Carpenter Thomas M, Cowell David, Freear Steven, Ghovanloo Maysam, Degertekin F Levent
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30308 USA. He is now with Broadcom, San Jose, CA 95131 USA.
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30308 USA. He is now with Onscale Inc., Redwood City, CA 94063 USA.
IEEE Sens J. 2019 Dec 15;19(24):12050-12058. doi: 10.1109/jsen.2019.2938079. Epub 2019 Aug 28.
A combined supply-inverted bipolar pulser and a Tx/Rx switch is proposed to drive capacitive micromachined ultrasonic transducers (CMUTs). The supply-inverted bipolar pulser adopts a bootstrap circuit combined with stacked transistors, which guarantees high voltage (HV) operation above the process limit without lowering device reliability. This circuit generates an output signal with a peak-to-peak voltage that is almost twice the supply level. It generates a bipolar pulse with only positive supply voltages. The Tx/Rx switch adopts a diode-bridge structure with the protection scheme dedicated to this proposed pulser. A proof- of-concept ASIC prototype has been implemented in 0.18-m HV CMOS/DMOS technology with 60 V devices. Measurement results show that the proposed pulser can safely generate a bipolar pulse of -34.6 to 45 V, from a single 45 V supply voltage. The Tx/Rx switch blocks the HV bipolar pulse, resulting in less than 1.6 V at the input of the receiver. Acoustic measurements are performed connecting the pulser to CMUTs with 2 pF capacitance and 8 MHz center frequency. The variation of acoustic output pressures for different pulse shapes were simulated with the large signal CMUT model and compared with the experimental results for transmit pressure optimization. A potential implementation of the methods using MEMS fabrication methods is also described.
提出了一种组合式电源反相双极脉冲发生器和收发开关，用于驱动电容式微机械超声换能器（CMUT）。电源反相双极脉冲发生器采用了一种结合堆叠晶体管的自举电路，可在不降低器件可靠性的情况下保证在工艺极限以上进行高压（HV）操作。该电路生成的输出信号的峰峰值电压几乎是电源电平的两倍。它仅用正电源电压就能生成双极脉冲。收发开关采用二极管桥结构，并带有专门为此提出的脉冲发生器设计的保护方案。已采用具有60V器件的0.18μm高压CMOS/DMOS技术实现了一个概念验证ASIC原型。测量结果表明，所提出的脉冲发生器能够从单个45V电源电压安全地生成-34.6至45V的双极脉冲。收发开关可阻断高压双极脉冲，使接收器输入端的电压低于1.6V。通过将脉冲发生器与电容为2pF、中心频率为8MHz的CMUT相连进行声学测量。利用大信号CMUT模型模拟了不同脉冲形状下声学输出压力的变化，并与用于发射压力优化的实验结果进行了比较。还描述了使用MEMS制造方法实现这些方法的一种潜在方案。
