Patent ID: 8890591
Filing Date: 2014-11-18
Classification: H03L

Abstract:
1. A circuit for improving crystal-less frequency generator's frequency stability, comprising: a temperature sensing circuit, for generating a temperature-related control signal, having an output for delivering said temperature-related control signal; a voltage sensing circuit, for generating a voltage-related control signal, having an output for delivering said voltage-related control signal; a frequency calibration circuit, having a first input for receiving a reference signal with a fixed and known frequency, having a second input for receiving a feedback signal, for generating a base frequency control word, having an output for delivering said base frequency control word; a frequency control word update circuit, having a first input for receiving said temperature-related control signal, having a second input for receiving said voltage-related control signal, having a third input for receiving said base frequency control word, for generating a frequency control word to compensate temperature- and voltage-related frequency variation and to correct frequency error introduced in the manufacture process, having an output for delivering said frequency control word; a crystal-less oscillator circuit, for generating an electrical voltage switching pattern having an oscillation frequency, for generating a base time unit from said switching pattern, having an output for delivering said base time unit; a Time-Average-Frequency direct period synthesizer, having a first input for receiving said frequency control word from said frequency control word update circuit, having a second input for receiving said base time unit from said crystal-less oscillator circuit, for generating a signal with a desired frequency that is accurate and stable, having an output for delivering said signal; a divider circuit, having an input for receiving said signal from said direct period synthesizer, for dividing received signal by a certain dividing ratio, having an output for delivering the divided signal as feedback signal; the output of said divider circuit is connected to the second input of frequency calibration circuit.