A Scalable High-Voltage Output Driver for Low-Voltage CMOS Technologies

A monolithic implementation of series connected MOSFETs for high-voltage switching applications is presented. Using a single low-voltage control signal to trigger the bottom MOSFET in the series stack, a voltage division across parasitic and inserted capacitances in the circuit is used to turn on the entire stack of devices. This voltage division both statically and dynamically safeguards the individual MOSFETs over the entire switching period. Because the output voltage is balanced across each device in the stack for the entire switching period, stress to the oxide and hot-carrier degradation are minimized, even in the event of transient over voltages. This circuit, termed the Stacked MOSFET, is ntimes scalable, allowing for the on-die control of voltages that are ntimes the fabrication processes rated operating voltage. The governing equations for this circuit are derived and reliable operation is demonstrated through simulation and experimental implementation in a 0.35-mum SOI CMOS process. The realized prototype is shown to handle 2times the nominal process operating voltage at a switching frequency of 20 MHz with an input-to-output delay of only 5.5 ns