Ring oscillator and method for starting ring oscillator

Patent metadata

Field	Value
Publication number	US-2022321107-A1
Application number	US-202217702470-A
Country	US
Kind code	A1
Filing date	Mar 23, 2022
Priority date	Mar 30, 2021
Publication date	Oct 6, 2022
Grant date	—

Abstract

A ring oscillator including: an oscillation circuit including an even number of inverters connected in a ring configuration, the oscillation circuit outputting a clock signal; plural potential fixing circuits respectively connected between pairs of the inverters, each of plural potential fixing circuits being switchable between a connected and a disconnected state in response to a first control signal; and an adjustment circuit that adjusts a drive capability of the inverters based on a second control signal, wherein, during startup, the drive capability is controlled to be a first capability, in which the potential fixing circuits are connected, by the first control signal, and wherein, after a predetermined time has elapsed after the first control signal is output, the drive capability is controlled to be a second capability, higher than the first capability, in which the potential fixing circuits are disconnected, by the second control signal.

First claim

What is claimed is:

1 . A ring oscillator comprising:
an oscillation circuit including an even number of inverters connected in a ring configuration, the oscillation circuit outputting a clock signal; a plurality of potential fixing circuits respectively connected between pairs of the inverters, each of the plurality of potential fixing circuits being switchable between a connected state and a disconnected state in response to a first control signal; and an adjustment circuit that adjusts a drive capability of the inverters based on a second control signal, wherein, during startup of the oscillation circuit, the drive capability is controlled to be a first capability, in which the potential fixing circuits are connected, by the first control signal, and wherein, after a predetermined time has elapsed after the first control signal is output, the drive capability is controlled to be a second capability, higher than the first capability, in which the potential fixing circuits are disconnected, by the second control signal.

2 . The ring oscillator according to claim 1 , wherein the drive capability is adjusted by current flowing to the inverters, and current corresponding to the second capability is greater than current corresponding to the first capability.

3 . The ring oscillator according to claim 1 , wherein the predetermined time is longer than a delay time of one cycle of the inverters.

4 . The ring oscillator according to claim 1 , wherein the potential fixing circuits are pull-up circuits or pull-down circuits.

5 . The ring oscillator according to claim 1 , wherein the second control signal is a signal in which the first control signal is delayed by a delay circuit having a delay time corresponding to the predetermined time.

6 . The ring oscillator according to claim 1 , further comprising a detection circuit that detects the clock signal,
wherein the second control signal is output from the detection circuit in a case in which the detection circuit has detected the clock signal.

7 . The ring oscillator according to claim 1 , further comprising a counter circuit that has a count time longer than the predetermined time,
wherein a counting operation of the counter circuit is started by the first control signal and is stopped by the second control signal.

8 . A method for starting a ring oscillator including: an oscillation circuit including an even number of inverters connected in a ring configuration and outputting a clock signal, a plurality of potential fixing circuits that are respectively connected between pairs of the inverters and are each switchable between being connected and being disconnected by a first control signal, and an adjustment circuit that adjusts the drive capability of the inverters based on a second control signal, the method comprising:
during startup of the oscillation circuit, controlling a drive capability to become a first capability, in which the potential fixing circuits are connected, by the first control signal; and after a predetermined time has elapsed after the first control signal is output, controlling the drive capability to become a second capability, higher than the first capability, in which the potential fixing circuits are disconnected, by the second control signal.

Assignees

• Lapis Tech Co Ltd

Inventors

• Furuta Manabu

Classifications

• H03K3/0315 Primary

  Ring oscillators · CPC title

• H03L7/0995 Primary

  the oscillator comprising a ring oscillator · CPC title

• H03B2200/0094

  Measures to ensure starting of oscillations · CPC title

• H03K3/014 Primary

  Modifications of generator to ensure starting of oscillations · CPC title

• H03K5/15046

  using a tapped delay line · CPC title