A programmable positive and negative high-voltage DC-DC converter dedicated for ultrasonic applications

This paper concerns the design and implementation of a fully integrated programmable high voltage CMOS DC-DC up-converter (PHVUC), followed by a negative high voltage doubler (NHVD) stage, which is dedicated to ultrasonic transmitters. The proposed PHVUC topology is based on a 5-stage charge pump circuit, and a level up shifter is used in each stage as a clock generator in order to increase exponentially the DC voltage. A floating gate technique is used to protect the gate oxide of transistors and a low power, low area level up shifter is proposed. Positive and negative HV DC levels are needed to drive ultrasound cells and are generated by a new NHVD. Post layout simulation results of the proposed circuits, using 0.8 μm CMOS/DMOS high-voltage process technology, show an output voltage range from -100V up to 200V and a fine programmability achieved with 98% gain voltage factor and 45mV output ripples at 2 MHz clock frequency. By implementing the floating gate technique, the power consumption of the level up shifter can be reduced to 50% compared to conventional one.