Precision oscillators that use imprecise components

Patent metadata

Field	Value
Publication number	US-10763832-B2
Application number	US-201715853015-A
Country	US
Kind code	B2
Filing date	Dec 22, 2017
Priority date	Dec 22, 2017
Publication date	Sep 1, 2020
Grant date	Sep 1, 2020

Abstract

Trimming components within an oscillator comprising: a trim-capable current source, wherein the trim-capable current source comprises a trimmable resistor and a trimmable current component, a comparator comprising a first input terminal that couples to the trim-capable current source and the second input terminal that couples to a reference voltage source, a switch coupled to the first input terminal and the trim-capable current source, and a trim-capable capacitor coupled to the switch, wherein the switch is coupled between the trim-capable capacitor and the trim-capable current source.

First claim

What is claimed is:

1. An oscillator comprising:
a trim-capable current source that comprises:
a trimmable resistor;
a trimmable current component;
a mirror transistor coupled to mirror a current through the trimmable resistor; and
a trim component coupled to the mirror transistor and operable to:
measure the current through the trimmable resistor; and
determine, based on the current through the trimmable resistor, an offset between a resistance of the trimmable resistor and a target resistance, wherein the trim-capable current source is operable to change the resistance of the trimmable resistor in response to the offset;

a comparator comprising a first input terminal that couples to the trim-capable current source and a second input terminal that couples to a reference voltage source;
a switch coupled to the first input terminal and the trim-capable current source; and
a trim-capable capacitor coupled to the switch, wherein the switch is coupled between the trim-capable capacitor and the trim-capable current source, and wherein the first input terminal of the comparator is electrically disconnected from the trim-capable capacitor when the switch is in a non-conductive state.

2. The oscillator of claim 1 , further comprising:
a second switch coupled to the first input terminal and the trim-capable current source; and
a second trim-capable capacitor coupled to the first input terminal, where the second switch is positioned between the trim-capable capacitor and the trim-capable current source.

3. The oscillator of claim 1 , further comprising a flip flop component, wherein an output terminal of the comparator is coupled to an input of the flip flop component.

4. The oscillator of claim 1 , wherein the trimmable resistor includes a resistor digital-to-analog circuit (RDAC) and the trimmable current component includes a current digital-to-analog circuit (IDAC).

5. The oscillator of claim 1 , wherein the trim-capable current source comprises a second trimmable resistor.

6. The oscillator of claim 5 , wherein the trimmable resistor and the second trimmable resistor are imprecise resistors.

7. The oscillator of claim 1 , wherein the trim-capable capacitor is a capacitor digital-to-analog circuit (CDAC).

8. An oscillator comprising:
a trim-capable current source that comprises:
a trimmable resistor;
a trimmable current component;
a mirror transistor coupled to mirror a current through the trimmable resistor; and
a trim component coupled to the mirror transistor and operable to:
measure the current through the trimmable resistor; and
determine, based on the current through the trimmable resistor, an offset between a resistance of the trimmable resistor and a target resistance, wherein the trim-capable current source is operable to change the resistance of the trimmable resistor in response to the offset;

a first comparator comprising a first input terminal that couples to the trim-capable current source and a second input terminal that couples to a reference voltage source;
a first switch coupled to the first input terminal and the trim-capable current source;
a first trim-capable capacitor coupled to the first switch, wherein the first switch is coupled between the first trim-capable capacitor and the trim-capable current source;
a second comparator comprising a third input terminal and a fourth input terminal, wherein the fourth input terminal is coupled to the reference voltage source; and
a second switch coupled between the trim-capable current source and the third input terminal of the second comparator.

9. The oscillator of claim 8 , further comprising a second trim-capable capacitor coupled to the third input terminal.

10. The oscillator of claim 8 , further comprising a flip flop, wherein an output terminal of the first comparator is coupled to an input of the flip flop and an output terminal of the second comparator is coupled to a second input of the flip flop.

11. An oscillator comprising:
a trim-capable current source configured to:
measure a current through a variable resistor that affects a first portion current of a capacitor charging current generated from the trim-capable current source;
determine, from the current, a resistance of the variable resistor;
determine an offset between the resistance of the variable resistor and a target resistance;
trim, based on the offset, the resistance of the variable resistor; and
trim the first portion current to adjust a proportion of the first portion current in the capacitor charging current generated from the trim-capable current source;

a comparator comprising a first input terminal that couples to the trim-capable current source and a second input terminal that couples to a reference voltage source; and
a trim-capable capacitor coupled to the first input terminal, wherein the trim-capable capacitor is configured to perform capacitor switching that controls a charge time of the trim-capable capacitor.

12. The oscillator of claim 11 , wherein the variable resistor comprises a resistor digital-to-analog circuit (RDAC) and the trim-capable current source comprises a current digital-to-analog circuit (IDAC).

13. The oscillator of claim 12 , wherein the RDAC includes a plurality of poly-resistors.

14. The oscillator of claim 11 , wherein the trim-capable current source is configured to generate a second portion current of the capacitor charging current that combines with the first portion current to form the capacitor charging current.

15. The oscillator of claim 11 , wherein the trim-capable capacitor is a capacitor digital-to-analog circuit (CDAC).

16. The oscillator of claim 15 , wherein the CDAC includes a 10 bit split-CDAC array.

17. A method comprising:
measuring a current through a trimmable resistor of an oscillator, wherein the trimmable resistor affects a first portion current of a capacitor charging current generated from a trim-capable current source of the oscillator;
determining an offset between the current through the trimmable resistor and a target resistance;
trimming the resistance of the trimmable resistor;
trimming the first portion current to adjust a proportion of the first portion current in the capacitor charging current generated from the trim-capable current source, wherein the capacitor charging current is a combination of the first portion current and a second portion current; and
trimming a trim-capable capacitor to perform capacitor switching that controls a charge time of the trim-capable capacitor.

18. The method of claim 17 , wherein the trimmable resistor includes a resistor digital-to-analog circuit (RDAC) to trim the resistance and the trim-capable current source includes a current digital-to-analog circuit (IDAC) to trim the first portion current that adjusts the proportion of the first portion current in the capacitor charging current.

19. The method of claim 17 , wherein the trim-capable capacitor is a capacitor digital-to-analog circuit (CDAC).

20. The method of claim 19 , wherein the CDAC includes a 10 bit split-CDAC array.

Assignees

• Texas Instruments Inc

Inventors

• Roy Aniruddha
• Agarwal Nitin
• Thinakaran Rajavelu

Classifications

• H03K4/502 Primary

  the capacitor being charged from a constant-current source · CPC title

• G05F3/262

  using field-effect transistors only · CPC title

• G05F3/245

  producing a voltage or current as a predetermined function of the temperature · CPC title

• G05F1/567

  for temperature compensation · CPC title

• H03K3/0231 Primary

  Astable circuits {(H03K3/0315 takes precedence)} · CPC title