Reducing Startup Time In A Crystal Oscillator

Patent metadata

Field	Value
Publication number	US-2024178794-A1
Application number	US-202218072682-A
Country	US
Kind code	A1
Filing date	Nov 30, 2022
Priority date	Nov 30, 2022
Publication date	May 30, 2024
Grant date	—

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

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; 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 wherein the transconductance circuit includes a transistor having a source, drain, and gate, and further including:
a first resistor coupled between a third input coupled to the gate and the source; and
a second resistor coupled between the third input and the drain.

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

8 . The oscillator apparatus of claim 1 and 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.

9 . 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.

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

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

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

13 . 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.

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

15 . The method of claim 13 wherein the difference between the first voltage and the second voltage is less than 5% of the rail-to-rail voltage.

16 . The method of claim 13 and further including, prior to the second time period, enabling a transconductance circuit.

17 . The method of claim 16 and 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.

18 . The method of claim 16 :
wherein the transconductance circuit includes a transistor having a gate and source; and wherein the step of enabling a transconductance circuit includes coupling an enabling gate-to-source voltage to the transistor.

19 . The method of claim 13 and 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.

20 . The method of claim 13 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

• H03B5/364 Primary

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

• H03B5/36 Primary

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