Temperature and voltage independent on-chip oscillator system and method

Abstract

A system and method for ensuring a substantially constant oscillator frequency that is substantially independent of the operating temperature and is substantially independent of variations of the supply voltage level where the oscillator is an on-chip oscillator without requiring significantly additional logic, e.g., not requiring the use of multiple comparators and enabling post packaging modifications of the oscillator frequency. The present invention utilizes one or more paired resistors as part of the RC oscillator where each of the one or more pairs are matched according to their temperature coefficient. That is, each pair includes a resistor with a positive temperature coefficient and a resistor with a corresponding negative temperature coefficient. In addition, the present invention enables post packaging modifications to the resistors based upon one or more program signals that can modify the resistance by forming a short circuit around one or more resistor pairs. The present invention also reduces the effect of voltage variations on the oscillator frequency by comparing a oscillatory signal with a reference signal that is a fixed percentage of the supply voltage. If the supply voltage signal drops, the capacitor of the RC oscillator charges at a slower rate but the oscillatory signal is compared to a reference signal having a lower value since the reference signal is a fixed percentage of the supply voltage.