Process, voltage and temperature tolerant clock generator

Abstract

Devices, methods, and systems are described that generate process, voltage and temperature tolerant clock generators, which can be used in low power and low cost applications. The clock generators eliminate the need for a crystal oscillator, are simple to implement, and can use a single frequency calibration step to initially tune the frequency to a reference frequency value, and to allow the clock generator to operate in the presence of process, voltage or temperature variations. One example clock circuit includes a voltage-controlled oscillator that provides a clock output, a gain circuit to receive a reference voltage as one input and a changeable voltage on another input. The clock circuit also includes a frequency-to-voltage convertor circuit that receives a reference current and produces the changeable voltage provided to gain circuit, while a ratio of the reference voltage to the reference current is constant.