Reducing startup time in a crystal oscillator

Patent metadata

Field	Value
Publication number	US-12074569-B2
Application number	US-202218072682-A
Country	US
Kind code	B2
Filing date	Nov 30, 2022
Priority date	Nov 30, 2022
Publication date	Aug 27, 2024
Grant date	Aug 27, 2024

Abstract

An oscillator apparatus, including a first node adapted to be coupled to a first terminal of a crystal oscillator; a second node adapted to be coupled to a second terminal of the crystal oscillator; a transconductance circuit; a first switch coupled between the first node and the second node; and a second switch coupled between the transconductance circuit and the second node.

First claim

What is claimed is:

1. An oscillator apparatus, comprising:
a first input adapted to be coupled to a first terminal of a crystal oscillator;
a second input adapted to be coupled to a second terminal of the crystal oscillator;
a transconductance circuit comprising a transistor having a source, drain, and gate;
a first resistor coupled between a third input coupled to the gate, and the source;
a second resistor coupled between the third input and the drain;
a first switch coupled between the first input and the second input; and
a second switch coupled between the transconductance circuit and the second input.

2. The oscillator apparatus of claim 1 and further including a controller adapted to provide a first control signal to the first switch and a second control signal to the second switch.

3. The oscillator apparatus of claim 2 :
wherein the controller is adapted to first assert the first control signal to close the first switch for a first period of time while the second switch is open; and
wherein the controller is adapted to second assert the second control signal to close the second switch for a second period of time while the first switch is open.

4. The oscillator apparatus of claim 2 :
wherein the controller is adapted to first assert the first control signal to close the first switch for a first period of time while the second switch is open; and
wherein the controller is adapted to second assert the second control signal to close the second switch for a second period of time while the first switch is open and to maintain an output oscillation signal of the oscillator apparatus.

5. An oscillator apparatus comprising:
a first node adapted to be coupled to a first terminal of a crystal oscillator;
a second node adapted to be coupled to a second terminal of the crystal oscillator;
a transconductance circuit;
a first switch coupled between the first node and the second node;
a second switch coupled between the transconductance circuit and the second node;
a first resistor coupled between a third node coupled to enable the transconductance circuit and a fourth node; and
a second resistor coupled between a current path to the transconductance circuit and the third node.

6. The oscillator apparatus of claim 1 , further including a crystal oscillator coupled between the first input and the second input.

7. The oscillator apparatus of claim 1 , further including:
a first capacitor coupled between the first input and a node adapted to be coupled to a low potential; and
a second capacitor coupled between the second input and the node adapted to be coupled to a low potential.

8. The oscillator apparatus of claim 1 , wherein the first input, the second input, the transconductance circuit, the first switch, and the second switch are part of an integrated circuit.

9. The oscillator apparatus of claim 8 , further including a crystal oscillator coupled between the first input and the second input and external from the integrated circuit.

10. The oscillator apparatus of claim 9 , further including clocked circuitry within the integrated circuit and coupled to at least one of the first and second inputs.

11. The oscillator apparatus of claim 1 , further including clocked circuitry coupled to at least one of the first and second inputs.

12. A method of operating an oscillator apparatus adapted to be coupled to a supply voltage, comprising:
in a first time period, coupling a first voltage to a first node adapted to be coupled to a first terminal of a crystal oscillator and a second node adapted to be coupled to a second terminal; and
in a second time period, after the first time period, maintaining the first voltage to the first terminal while coupling a second voltage to the second terminal; and
wherein a difference between the first voltage and the second voltage is less than a rail-to-rail voltage.

13. The method of claim 12 , wherein the difference between the first voltage and the second voltage is less than 50% of the rail-to-rail voltage.

14. The method of claim 12 , wherein the difference between the first voltage and the second voltage is less than 5% of the rail-to-rail voltage.

15. The method of claim 12 , further including, prior to the second time period, enabling a transconductance circuit.

16. The method of claim 15 , further including, in the second time period, coupling a first node of the transconductance circuit to the first terminal and coupling a second node of the transconductance circuit to the second terminal.

17. The method of claim 15 :
wherein the transconductance circuit includes a transistor having a gate and source; and
wherein the step of enabling the transconductance circuit includes coupling an enabling gate-to-source voltage to the transistor.

18. The method of claim 12 , further including, in a third time period after the second time period, clocking a circuit with an oscillating signal between the first terminal and the second terminal.

19. The method of claim 12 , further comprising:
in the first time period, closing a first switch between the first node and the second node; and
in the second time period, opening the first switch and closing a second switch between the second terminal and an enabling node of a transconductance circuit.

Assignees

• Texas Instruments Inc

Inventors

• Paul Animesh

Classifications

• H03B5/06

  Modifications of generator to ensure starting of oscillations · CPC title

• H03B5/362

  the amplifier being a single transistor (H03B5/364 - H03B5/368 take precedence) · CPC title

• H03B5/36 Primary

  active element in amplifier being semiconductor device ({H03B5/323, H03B5/326} , H03B5/38 take precedence) · CPC title

• H03B5/364 Primary

  the amplifier comprising field effect transistors (H03B5/366 takes precedence) · CPC title