A Trimming-Less External-RC Relaxation Oscillator With Self-Calibrating Current Reference for a SiC Active Gate Driver Application

This work presents a reference frequency and current generator circuit with high stability to temperature and process variations without requiring any post-fabrication trimming. The design serves as the reference generator in an active gate driver IC for Silicon Carbide transistors. It incorporates an 8MHz relaxation oscillator and a 12μA self-calibrating current reference. Both circuits share a parallel-connected discrete off-chip resistor and capacitor to eliminate the impact of on-chip process variations. A temperature stability of 45ppm/°C for the frequency and 54ppm/°C for the current is achieved by applying a closed-loop comparator error feedback as well as a resistor temperature compensation. The overall frequency and current standard deviation for process variations is 0.70% and 0.47%. The circuit is fabricated in a 0.18μm BCD technology.