Continuous cascode voltage control for protection of low voltage devices

Abstract

Methods and apparatuses for protecting a low voltage (LV) circuit implemented with LV transistors are presented. Protection is provided via a protection circuit operating in a high voltage domain defined by a varying supply voltage and a reference ground. The protection circuit generates high side, VH, and low side, VL, voltages to the LV circuit, while protecting the LV circuits from high voltage and maintaining a minimum difference voltage, VH−VL. The protection circuit generates the difference voltage based on a voltage across a resistor of a resistor ladder that is coupled between the varying supply voltage and the reference ground. The protection circuit includes a clamp circuit that limits the minimum difference voltage for low values of the supply voltage. The protection circuit generates the difference voltage according to a nonlinear transfer function of the supply voltage that includes two linear segments having different slopes and a nonlinear segment that provides a continuous and smooth transition between the two linear segments.

Dependencies are inferred from the claim text.