# US 10,312,887 B2 · Self-biasing integrated oscillator without bandgap reference

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- Number: US 10,312,887 B2
- Document ID: US10312887B2
- Status: Granted
- Kind: B2
- Application number: 15/365,605
- Filed: 2016-11-30
- Published: 2018-05-31
- Granted: 2019-06-04
- Earliest claimed: 2016-11-30
- Assignees: OmniVision Technologies, Inc.
- Applicants: OmniVision Technologies, Inc.
- Inventors: Li Yang; Charles Qingle Wu
- Web page: https://patentgrep.com/patent/US10312887B2

## CPC

- H03K 3/0231: Astable circuits {(H03K3/0315 takes precedence)}
- H03B 5/24: active element in amplifier being semiconductor device (H03B5/26 takes precedence)
- H03K 3/011: Modifications of generator to compensate for variations in physical values, e.g. voltage, temperature {(to maintain energy constant H03K3/015)}
- H03K 3/012: Modifications of generator to improve response time or to decrease power consumption
- H03K 3/037: Bistable circuits
- H03K 3/354: Astable circuits
- H03K 3/36: by the use, as active elements, of semiconductors, not otherwise provided for
- H03K 4/50: in which a sawtooth voltage is produced across a capacitor
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H)

## Abstract

An integrated oscillator has an R-S flipflop; a first and second capacitor; a current source transistor; first and second current-steering transistors, each having a source coupled to the current source transistor, with drains coupled to the first and second capacitor respectively. The first current-steering transistor has gate coupled to a first output of the R-S flipflop, and the second current-steering transistor has gate coupled to a second output of the R-S flipflop. The oscillator has a first sense inverter having input from the first capacitor and powered by a feedback circuit adapted to sense voltages on the first and second capacitor; and a second sense inverter having input from the second capacitor and powered by the feedback circuit. The R-S flipflop has a first input coupled to an output of the first sense inverter and a second input coupled to an output of the second sense inverter.

## Claims

### Claim 1

An integrated oscillator comprising:
an R-S flipflop;
a first and a second capacitor;
a first current source transistor having a drain and a gate;
a first and a second current-steering transistor, each having a source coupled to the drain of the first current source transistor, a drain of the first current-steering transistor coupled to the first capacitor, and a drain of the second current-steering transistor coupled to the second capacitor, the first current-steering transistor having a gate coupled to a first output of the R-S flipflop, and the second current-steering transistor having a gate coupled to a second output of the R-S flipflop;
a first sense inverter having input coupled to the first capacitor, the first sense inverter being powered by a feedback circuit adapted to sense voltages on the first and second capacitor; and
a second sense inverter having input coupled to the second capacitor and powered by the feedback circuit;
wherein the R-S flipflop has a first input coupled to an output of the first sense inverter and a second input coupled to an output of the second sense inverter; and
wherein the first input of the R-S flipflop is an active-low SET input.

### Claim 2

An integrated oscillator comprising:
an R-S flipflop;
a first and a second capacitor;
a first current source transistor having a drain and a gate;
a first and a second current-steering transistor, each having a source coupled to the drain of the first current source transistor, a drain of the first current-steering transistor coupled to the first capacitor, and a drain of the second current-steering transistor coupled to the second capacitor, the first current-steering transistor having a gate coupled to a first output of the R-S flipflop, and the second current-steering transistor having a gate coupled to a second output of the R-S flipflop;
a first sense inverter having input coupled to the first capacitor, the first sense inverter being powered by a feedback circuit adapted to sense voltages on the first and second capacitor; and
a second sense inverter having input coupled to the second capacitor and powered by the feedback circuit;
wherein the R-S flipflop has a first input coupled to an output of the first sense inverter and a second input coupled to an output of the second sense inverter; and
wherein the feedback circuit comprises a first differential amplifier having an inverting and a noninverting input, the inverting input coupled through a first resistor to the first capacitor and through a second resistor to the second capacitor, and a third capacitor coupled between the inverting input and an output of the differential amplifier.

### Claim 3 (depends on 2)

The integrated oscillator of claim 2 wherein the gate of the first current source transistor is coupled to an output of a bias circuit comprising an reference inverter having input coupled to output, a second differential amplifier having a noninverting input coupled to the output of the reference inverter and an inverting input coupled to the output of the bias circuit.

### Claim 4 (depends on 3)

The integrated oscillator of claim 3 wherein the reference inverter has a threshold matched to the first sense inverter.

### Claim 5 (depends on 2)

The integrated oscillator of claim 2 wherein the R-S flipflop has at least one additional input configured to place the R-S flipflop in a known state for testing.

### Claim 6 (depends on 1)

The integrated oscillator of claim 1 wherein the R-S flipflop has at least one additional input configured to place the R-S flipflop in a known state for testing.

### Claim 7

A method of generating a signal comprising:
generating a first controlled current;
switching the first controlled current onto a selected capacitor, the selected capacitor selected from the group consisting of a first capacitor and a second capacitor according to at least one output of an R-S flipflop;
detecting a voltage on the first capacitor reaching an oscillator threshold voltage and switching a state of the R-S flipflop; and
detecting a voltage on the second capacitor reaching the oscillator threshold voltage and switching the state of the R-S flipflop;
wherein the oscillator threshold voltage is a threshold voltage of a reference inverter comprising an N type transistor having source coupled to ground, gate coupled to input of the inverter, and drain coupled to output of the inverter, a P type transistor having source coupled to a control voltage, gate coupled to an input of the inverter, and drain coupled to the output of the inverter.

### Claim 8 (depends on 7)

The method of claim 7 wherein the reference inverter is matched to a sense inverter that detects the voltage on the first capacitor.

### Claim 9 (depends on 7)

The method of claim 7 wherein the control voltage is determined by a feedback control circuit having input from the voltage on the first capacitor and the voltage on the second capacitor.