Supply-Inverted Bipolar Pulser and Tx/Rx Switch for CMUTs Above the Process Limit for High Pressure Pulse Generation

Area of Science:

• Electrical Engineering
• Materials Science
• Biomedical Engineering

Background:

• Capacitive micromachined ultrasonic transducers (CMUTs) require specialized driving circuitry for optimal performance.
• Existing high-voltage (HV) pulser designs often face limitations in output voltage and reliability.
• Efficient transmit/receive (Tx/Rx) switching is crucial for CMUT-based systems.

Purpose of the Study:

• To propose and validate a novel combined supply-inverted bipolar pulser and Tx/Rx switch for driving CMUTs.
• To achieve high-voltage bipolar pulse generation from a single positive supply.
• To ensure reliable operation and effective signal isolation for CMUT applications.

Main Methods:

• A supply-inverted bipolar pulser utilizing a bootstrap circuit and stacked transistors was designed.
• A dedicated diode-bridge Tx/Rx switch with a protective scheme was developed.
• A proof-of-concept ASIC prototype was fabricated using 0.18-μm HV CMOS/DMOS technology.
• Acoustic measurements were performed using CMUTs with specific capacitance and center frequency.

Main Results:

• The pulser generated a bipolar pulse from -34.6 V to 45 V using a single 45 V supply.
• The Tx/Rx switch effectively blocked the HV pulse, limiting receiver input to <1.6 V.
• Simulations and experimental results were compared for transmit pressure optimization with CMUTs.

Conclusions:

• The proposed integrated pulser and switch effectively drives CMUTs with high-voltage bipolar pulses from a single supply.
• The design offers enhanced reliability and performance for CMUT applications.
• The study demonstrates a viable approach for advanced CMUT system development, including potential MEMS fabrication.