Patent ID: 7254157

Claim:
A spread spectrum clock generator, comprising: a fixed voltage source for providing a first voltage; an analog multiplexer including a chain of serially-connected resistors of a voltage divider, a plurality of transistors, and a controller adapted to selectively turn on and off each of the transistors for each of a plurality of time periods, wherein the chain of serially-connected resistors of the voltage divider is coupled between the first voltage from the fixed voltage source and a second voltage, and each of the transistors selectively couples a respective node that is between two of the serially-connected resisters in the chain of the voltage divider, to an output of the analog multiplexer; a ring oscillator including a plurality of inverters that have a voltage supply coupled to the output of the analog multiplexer; a buffer that couples the output of the analog multiplexer to the voltage supply of the inverters of the ring oscillator, wherein the buffer comprises a unity gain amplifier; and a range shifter that includes another chain of serially-connected resistors of the voltage divider, another plurality of transistors, and another controller adapted to selectively turn on each of the another plurality of transistors, wherein the another chain of serially-connected resistors is coupled between the second voltage of the analog multiplexer and ground, and each of the another plurality of transistors selectively couples to the ground a respective node, which is between two of the serially-connected resisters in the another chain of the voltage divider.