Wobble-based on-chip calibration circuit for temperature independent oscillators

An automatic calibration circuit for temperature- and process-independent oscillators and timing circuits is presented. The circuit monitors the dynamic gate-source voltage of a MOS transistor of which the temperature is changing. By adapting the bias current through this transistor towards the zero-temperature-coefficient point of the V-GS, the gate-source voltage can be used in temperature- independent timing circuits. Because of the dynamic nature of this regulation circuit, the technique is insensitive to mismatch and process variations. The presented technique is applied to a low-noise oscillator to make it less temperature sensitive with a factor of 8.