# US 9,438,165 B2 · RC oscillator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,165 B2 - Document ID: US9438165B2 - Status: Granted - Kind: B2 - Application number: 14/509,754 - Filed: 2014-10-08 - Published: 2016-04-14 - Granted: 2016-09-06 - Earliest claimed: 2014-10-08 - Assignees: Silicon Laboratories Inc. - Applicants: Silicon Laboratories Inc. - Inventors: Matthew R. Powell; Axel Thomsen; Nicholas M. Atkinson - Web page: https://patentgrep.com/patent/US9438165B2 ## CPC - 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 3/0231: Astable circuits {(H03K3/0315 takes precedence)} - 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) - 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) ## Abstract A method includes using a current source to provide a charging current to a capacitor of a resistor-capacitor (RC) tank of an RC oscillator. The method includes using a resistor of the current source as a resistor for the RC tank. ## Claims ### Claim 1 A method comprising: using a current source to provide a charging current to a capacitor of a resistor-capacitor (RC) tank of an RC oscillator; using a resistor of the current source as a resistor for the RC tank; and communicating the charging current to the capacitor using a charging path, wherein using the charging path comprises communicating the charging current to the capacitor using an amplifier and using the amplifier to amplify the voltage to generate a signal to turn on a discharge path to discharge the capacitor, wherein using the amplifier to amplify the voltage comprises operating a first transistor in a linear mode of operation to communicate the charging current to the capacitor and transitioning the first transistor to an off state near or at the end of a first part of an oscillation cycle for the RC oscillator to increase the amplification of the signal. ### Claim 2 (depends on 1) The method of claim 1, further comprising using a resistance of the resistor to regulate the charging current. ### Claim 3 (depends on 1) The method of claim 1, wherein: the first transistor has a controlled current path in series with the capacitor; and using the resistor comprises providing a second transistor having a controlled current path in series with the resistor and coupling control terminals of the first and second transistors together. ### Claim 4 (depends on 1) The method of claim 1, further comprising: using the RC oscillator in a clock system for an electronic device to provide a relatively low frequency clock signal to change a state of an analog component of the electronic device and using a clock source of the clock system other than the RC oscillator to provide a relatively high frequency clock signal to change a state of a digital component of the electronic device. ### Claim 5 (depends on 1) The method of claim 1, further comprising activating a transistor to discharge the capacitor. ### Claim 6 (depends on 1) The method of claim 1, wherein using the current source comprises using a VGS/R current source or a delta VGS/R current source to provide the charging current. ### Claim 7 An apparatus comprising: a resistor-capacitor (RC) tank circuit formed from a resistor and a capacitor and having an oscillation cycle comprising a first part of the cycle in which the capacitor is charged and a second part of the cycle in which the capacitor is discharged; a discharge path circuit to discharge the capacitor during the second part of the cycle; and a charge path circuit to communicate a charging current to the capacitor, wherein the charge path circuit comprises an amplifier to communicate the charging current and to amplify a voltage of the capacitor to generate a signal to control coupling of the discharge path circuit to the capacitor, wherein the amplifier comprises a transistor to operate in a linear mode of operation to communicate the charging current to the capacitor and transition to an off state near or at the end of the first part of the cycle to increase the amplification of the signal. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the amplifier comprises a single-ended amplifier to amplify the voltage. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein the discharge path circuit comprises a switch to be selectively turned on by the signal to discharge the capacitor. ### Claim 10 (depends on 7) The apparatus of claim 7, further comprising a digital buffer to reshape the voltage of the capacitor to generate a clock signal. ### Claim 11 An apparatus comprising: an integrated circuit comprising a processor core and a clock system comprising a plurality of clock sources and being adapted to select a clock signal provided by a given clock source of the plurality of clock sources and to provide the selected clock signal to at least one component of the integrated circuit, wherein the given clock source comprises a resistor-capacitor (RC) oscillator comprising: a current source to provide a regulated current and comprising a resistor; an RC tank circuit comprising the resistor and a capacitor to establish a period of the clock signal; and a charge path circuit to charge the capacitor using a charging current, wherein the charge path circuit comprises an amplifier to communicate the charging current to the capacitor and amplify a voltage of the capacitor to generate a signal to control operation of a discharge circuit to discharge the capacitor, wherein the RC oscillator is associated with an oscillation cycle, and the amplifier comprises a first transistor to operate in a linear mode of operation to communicate the charging current to the capacitor and transition to an off state near or at the end of a first part of the oscillation cycle to increase the amplification of the signal. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein a resistance of the resistor controls a magnitude of the charging current. ### Claim 13 (depends on 11) The apparatus of claim 11, wherein the current source comprises: a second transistor having a first controlled current path in series with the resistor; a third transistor having a second controlled current path in series with the capacitor; and a current mirror to couple the first and second controlled current paths together. ### Claim 14 The apparatus of 11, wherein the current source comprises a VGS/R current source or a delta VGS/R current source.