Aspects of the invention include a first voltage sensitive circuit including first transistors, the first transistors being coupled together so as to be operatively coupled to a first current source. A second voltage sensitive circuit includes second transistors, the second transistors being coupled together so as to be operatively coupled to a second current source, the first voltage sensitive circuit being coupled to the second voltage sensitive circuit to form a delay chain, the first and second current sources being responsive to changes in voltage of a power supply according to a voltage reference. A voltage sensitive current reference module is coupled to the first and second current sources and configured to supply the voltage reference to the first and second current sources, the voltage sensitive current reference module being responsive to changes in the voltage of the power supply.