Patent ID: 7609119

Claim:
A reference voltage generator for an external logic device, comprising: a ring oscillator circuit having a delay characteristic responsive to temperature, process, and/or power supply voltage variations, wherein the delay characteristic is related to a gate propagation characteristic of the external logic device; a reference clock generator; a first unit configured to detect a phase/frequency difference between a phase/frequency of the reference clock generator and a phase/frequency of the ring oscillator circuit, wherein the first unit is further configured to apply a first reference voltage to the external logic device, and wherein the first unit is configured to supply the first reference voltage to the plurality of logic gates of the ring oscillator circuit, and wherein the first reference voltage indicates the phase/frequency difference; and a second unit configured to measure a voltage swing of the ring oscillator circuit, wherein the second unit is further configured to apply a second reference voltage, independent of the phase/frequency of the ring oscillator circuit, to the external logic device and to supply the second reference voltage to the plurality of logic gates of the ring oscillator circuit, and wherein the second reference voltage is indicative of the measured voltage swing; wherein the ring oscillator circuit is configured to respond to the first and second reference voltages by altering an output signal to settle the first and second reference voltages at a first level and a second level, respectively, to stabilize a propagation delay of the external logic device.