A voltage reference connects to a voltage-to-current converter to generate a reference current dependent on the reference voltage. Outputs of a toggle-type flip flop connect to switching transistors controlling the reference current charging capacitors. The toggling of the flip-flop is controlled by comparing the capacitor voltages to the reference voltage, such that the toggle frequency is proportional to the time charging the capacitors. Optionally, temperature compensation data, representing a magnitude and direction rotation of the frequency versus temperature characteristic is stored and, based on a sensed temperature, retrieved to modify the reference current.