Digitally reconfigurable ultra-high precision internal oscillator

Patent metadata

Field	Value
Publication number	US-9503100-B1
Application number	US-201514927649-A
Country	US
Kind code	B1
Filing date	Oct 30, 2015
Priority date	Oct 30, 2015
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

A system, method and apparatus for tuning an internal oscillator to a desired frequency F1 is shown and uses an RC delay element that comprises a resistor, a capacitor and a comparator. The method includes receiving a clock signal from an oscillator to be tuned, triggering charging of the RC delay element, and N clock cycles after triggering the charging, the method determines whether the charge on the precision RC delay element is higher than or lower than a reference voltage. Correction to the clock frequency is based on the results.

First claim

What is claimed is:

1. A method of tuning an internal oscillator to a desired frequency F1, the method using an RC delay element that comprises a resistor, a capacitor and a comparator, the method comprising:
receiving a clock signal from an oscillator to be tuned;
triggering charging of the RC delay element;
at M clock cycles from triggering the charging, obtaining a first result that indicates whether the voltage on the RC delay element is higher than or lower than a reference voltage;
providing corrective feedback to the oscillator based on the first result;
after obtaining the first result, charging the capacitor to twice the reference voltage and triggering discharging of the RC delay element;
at N clock cycles from triggering the discharging, obtaining a second result that indicates whether the charge on the RC delay element is higher than or lower than the reference voltage;
determining whether the first and second results are the same;
if the first and second results are not the same, performing the providing; and
if the first and second results are the same, adjusting the values of M and N based on the results and refraining from providing corrective feedback to the oscillator.

2. An integrated circuit (IC) chip comprising:
a frequency tuning module coupled to provide a control signal to an oscillator and to receive a clock signal from the oscillator; and
a RC delay element comprising a digital buffer, a resistor, a capacitor and a comparator, the resistor being connected between the digital buffer and a first input of the comparator, a second input of the comparator receiving a reference voltage, the capacitor having a terminal connected between the resistor and the first input of the comparator, and the digital buffer being connected to receive a start trigger;
wherein the frequency tuning module is configured to perform the following:
triggering charging of the RC delay element;
after M clock cycles from triggering the charging, obtaining a first result from the comparator;
providing corrective feedback to the oscillator based on the first result,
wherein the frequency tuning module is further configured to perform:
after obtaining the first result, further charging the capacitor to twice the reference voltage;
triggering discharging of the precision RC delay element;
after N clock cycles from triggering the discharging, obtaining a second result from the comparator;
determining whether the first and the second results are the same;
if the first and second results are the same, adjusting the relationship between M and N and not adjusting the frequency of the clock signal; and
if the first and second results are not the same, performing the providing.

Assignees

• Texas Instruments Inc

Inventors

• Das Abhijit Kumar

Classifications

• G06F1/04

  Generating or distributing clock signals or signals derived directly therefrom · CPC title

• H03L7/02 Primary

  using a frequency discriminator comprising a passive frequency-determining element · CPC title

• H03K5/135 Primary

  by the use of time reference signals, e.g. clock signals · CPC title

• G06F1/08

  Clock generators with changeable or programmable clock frequency · CPC title