Oscillator with frequency control

Patent metadata

Field	Value
Publication number	US-12418278-B2
Application number	US-202318321105-A
Country	US
Kind code	B2
Filing date	May 22, 2023
Priority date	Jan 19, 2023
Publication date	Sep 16, 2025
Grant date	Sep 16, 2025

Abstract

A circuit includes a ring oscillator, a current source, an amplifier, a resistor-capacitor (RC) network, and a bias circuit. The current source is configured to power the ring oscillator. The amplifier is configured to control the current source. The amplifier has a first amplifier input and a second amplifier input. The RC network is coupled to the first amplifier input. The bias circuit is coupled to the second amplifier input. The bias circuit is configured to selectably set a frequency range of the ring oscillator, and selectably set a frequency of the ring oscillator within the frequency range.

First claim

What is claimed is:

1. A circuit comprising:
a ring oscillator having a power input;
a current source having a control input and a current output, the current output coupled to the power input, and
an amplifier having a first amplifier input, a second amplifier input and an amplifier output, the amplifier output coupled to the control input of the current source;
a first resistor and a first capacitor coupled in parallel and further coupled to the first amplifier input; and
a bias circuit coupled to the second amplifier input, the bias circuit including:
second, third, fourth, and fifth resistors coupled in series;
a first switch coupled between the second amplifier input and a first terminal of the third resistor;
a second switch coupled between the second amplifier input and a second terminal of the third resistor;
a third switch coupled in parallel with the fourth resistor; and
a fourth switch coupled in parallel with the fifth resistor,

wherein:
a first resistance of the second resistor is equal to a second resistance of the third resistor;
a third resistance of the fourth resistor is equal to a fourth resistance of the fifth resistor; and
the first resistance is larger than the third resistance.

2. The circuit of claim 1 , wherein
the fourth switch is further coupled to a ground terminal.

3. The circuit of claim 1 , wherein the second, third, fourth, and fifth resistors are coupled in series between a power terminal and a ground terminal.

4. The circuit of claim 1 , wherein:
the first resistance is at least twice the third resistance.

5. The circuit of claim 1 , wherein the first resistor has a fixed resistance.

6. The circuit of claim 1 , further comprising:
a fifth switch coupled between a first terminal of the first capacitor and a first terminal of the first resistor; and
a sixth switch coupled between the first terminal of the first capacitor and a power terminal.

7. The circuit of claim 1 , wherein the bias circuit is configured to:
selectably set a frequency range of the ring oscillator by controlling the first switch and the second switch.

8. The circuit of claim 7 , wherein the bias circuit is configured to:
selectably set a frequency of the ring oscillator within the frequency range by controlling the third switch and the fourth switch.

9. A circuit comprising:
a ring oscillator;
a current source configured to power the ring oscillator;
an amplifier configured to control the current source, the amplifier having a first amplifier input and a second amplifier input;
a resistor-capacitor (RC) network coupled to the first amplifier input; and
a bias circuit coupled to the second amplifier input and comprising:
a first resistor, a second resistor, a third resistor, and a fourth resistor coupled in series;
a first switch coupled between a first terminal of the second resistor and the second amplifier input;
a second switch coupled between a second terminal of the second resistor and the second amplifier input;
a third switch coupled in parallel with the third resistor; and
a fourth switch coupled in parallel with the fourth resistor,

wherein the bias circuit is configured to:
selectably set a frequency range of the ring oscillator; and
selectably set a frequency of the ring oscillator within the frequency range, and

wherein:
a first resistance of the first resistor is equal to a second resistance of the second resistor;
a third resistance of the third resistor is equal to a fourth resistance of the fourth resistor; and
the first resistance is larger than the third resistance.

10. The circuit of claim 9 , wherein the bias circuit is configured to:
close the first switch and open the second switch to selectably set the ring oscillator to a first frequency range; and
close the second switch and open the first switch to selectably set the ring oscillator to a second frequency range.

11. The circuit of claim 8 , wherein:
the bias circuit is configured to:
close the third switch to selectably set the frequency of the ring oscillator to a first frequency in the frequency range; and
close the fourth switch to selectably set the frequency of the ring oscillator to a second frequency in the frequency range.

12. The circuit of claim 9 , wherein:
the fourth switch is further coupled to a ground terminal.

13. The circuit of claim 9 , wherein:
the first resistance is at least twice the third resistance.

14. The circuit of claim 9 , wherein:
the RC network includes:
a fifth resistor coupled between the first amplifier input and a ground terminal;
a capacitor coupled in parallel with the fifth resistor;
a fifth switch coupled between the capacitor and a power terminal; and
a sixth switch coupled between the fifth resistor and the capacitor.

15. The circuit of claim 9 , wherein the first, second, third, and fourth resistors are coupled in series between a power terminal and a ground terminal.

16. A microcontroller circuit comprising:
a processor;
an oscillator circuit coupled to the processor, the oscillator circuit including:
a ring oscillator;
a current source configured to power the ring oscillator;
an amplifier configured to control the current source, the amplifier having a first amplifier input and a second amplifier input;
a resistor-capacitor (RC) network coupled to the first amplifier input; and
a bias circuit coupled to the second amplifier input, the bias circuit including:
a coarse adjustment circuit including:
a first resistor and a second resistor coupled in series;
a first switch coupled between a first terminal of the second resistor and the second amplifier input; and
a second switch coupled between a second terminal of the second resistor and the second amplifier input; and

a fine adjustment circuit including:
a third resistor and a fourth resistor coupled in series with the first resistor and the second resistor;
a third switch coupled in parallel with the third resistor; and
a fourth switch coupled in parallel with the fourth resistor,

wherein:
a first resistance of the first resistor is equal to a second resistance of the second resistor;
a third resistance of the third resistor is equal to a fourth resistance of the fourth resistor; and
the first resistance is larger than the third resistance.

17. The microcontroller circuit of claim 16 , wherein the first resistance is at least twice the third resistance.

18. The microcontroller circuit of claim 16 , wherein the bias circuit is configured to:
close the first switch and open the second switch to selectably set the ring oscillator to a first frequency range; and
close the second switch and open the first switch to selectably set the ring oscillator to a second frequency range.

19. The microcontroller circuit of claim 16 , wherein the coarse adjustment circuit is configured to selectably set a frequency range of the ring oscillator, and the fine adjustment circuit is configured to selectably set a frequency of the ring oscillator within the frequency range.

20. The microcontroller circuit of claim 19 , wherein the bias circuit is configured to:
close the third switch to selectably set the ring oscillator to a first frequency in the frequency range; and
close the fourth switch to selectably set the ring oscillator to a second frequency in the frequency range.

Assignees

• Texas Instruments Inc

Inventors

• Griffith Danielle

Classifications

• H03K17/687

  the devices being field-effect transistors · CPC title

• H03K17/063

  in field-effect transistor switches · CPC title

• H03K3/0315 Primary

  Ring oscillators · CPC title