# US 12,119,828 B1 · Clock synthesizer with dual control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,828 B1 - Document ID: US12119828B1 - Status: Granted - Kind: B1 - Application number: 18/198,797 - Filed: 2023-05-17 - Granted: 2024-10-15 - Earliest claimed: 2023-05-17 - Assignees: Synopsys, Inc. - Applicants: Synopsys, Inc. - Inventors: Dirk Pfaff; Ralph Mason; Robert Abbott; Christopher Falkingham - Web page: https://patentgrep.com/patent/US12119828B1 ## CPC - H03K 5/135: by the use of time reference signals, e.g. clock signals - H03K 5/00006: {Changing the frequency (modulating pulses H03K7/00; frequency dividers H03K21/00 - H03K29/00; additive or subtractive mixing of two pulse rates into one G06F7/605; pulse rate dividers G06F7/68)} - H03K 5/26: the characteristic being duration, interval, position, frequency, or sequence - 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 The present disclosure describes circuits (e.g., clock synthesizers) and methods for producing alternating signals. A clock synthesizer includes an oscillator, a voltage control circuit, and a frequency control circuit. The oscillator produces an output signal with a frequency. The voltage control circuit produces a control voltage for the oscillator based on the frequency of the output signal. The frequency control circuit produces a control signal for the oscillator based on (i) an input voltage to the frequency control circuit and (ii) the control voltage. The control signal causes the oscillator to adjust the frequency of the output signal such that the voltage control circuit adjusts the control voltage to be closer to the input voltage. ## Claims ### Claim 1 A clock synthesizer comprising: an oscillator arranged to produce an output signal with a frequency; a voltage control circuit arranged to produce a control voltage for the oscillator based on the frequency of the output signal; and a frequency control circuit arranged to produce a control signal for the oscillator based on (i) an input voltage to the frequency control circuit and (ii) the control voltage, wherein the control signal causes the oscillator to adjust the frequency of the output signal such that the voltage control circuit adjusts the control voltage to be closer to the input voltage. ### Claim 2 (depends on 1) The clock synthesizer of claim 1, wherein the oscillator comprises a first set of voltage controlled capacitors and a second set of voltage controlled capacitors. ### Claim 3 (depends on 2) The clock synthesizer of claim 2, wherein a capacitance of the first set of voltage controlled capacitors varies based on the control voltage. ### Claim 4 (depends on 2) The clock synthesizer of claim 2, wherein a capacitance of the second set of voltage controlled capacitors varies based on the control signal. ### Claim 5 (depends on 1) The clock synthesizer of claim 1, wherein the frequency control circuit comprises a comparator arranged to produce a comparator output based on the control voltage and the input voltage. ### Claim 6 (depends on 5) The clock synthesizer of claim 5, wherein the frequency control circuit further comprises a filter arranged to produce the control signal based on the comparator output. ### Claim 7 (depends on 6) The clock synthesizer of claim 6, wherein the filter comprises an integrator arranged to integrate the comparator output and a scaling factor. ### Claim 8 (depends on 7) The clock synthesizer of claim 7, wherein the filter further comprises a modulator arranged to produce an offset for an output of the integrator. ### Claim 9 (depends on 8) The clock synthesizer of claim 8, wherein the filter further comprises an encoder arranged to convert the offset and the output of the integrator from binary to thermometer code to produce the control signal. ### Claim 10 (depends on 1) The clock synthesizer of claim 1, wherein the input voltage is half of a supply voltage to the voltage control circuit. ### Claim 11 A method for producing an alternating signal, the method comprising: producing, by an oscillator, an output signal with a frequency; producing, by a voltage control circuit, a control voltage for the oscillator based on the frequency of the output signal; producing, by a frequency control circuit, a control signal for the oscillator based on (i) an input voltage to the frequency control circuit and (ii) the control voltage; adjusting, by the oscillator and based on the control signal, the frequency of the output signal; and adjusting, by the voltage control circuit, the control voltage to be closer to the input voltage after the oscillator adjusts the frequency of the output signal. ### Claim 12 (depends on 11) The method of claim 11, wherein the oscillator comprises a first set of voltage controlled capacitors and a second set of voltage controlled capacitors. ### Claim 13 (depends on 12) The method of claim 12, wherein a capacitance of the first set of voltage controlled capacitors varies based on the control voltage. ### Claim 14 (depends on 12) The method of claim 12, wherein a capacitance of the second set of voltage controlled capacitors varies based on the control signal. ### Claim 15 (depends on 11) The method of claim 11, further comprising producing, by a comparator of the frequency control circuit, a comparator output based on the control voltage and the input voltage. ### Claim 16 (depends on 15) The method of claim 15, wherein the frequency control circuit further comprises a filter arranged to produce the control signal based on the comparator output. ### Claim 17 (depends on 16) The method of claim 16, further comprising integrating, by an integrator of the filter, the comparator output and a scaling factor. ### Claim 18 (depends on 17) The method of claim 17, further comprising producing, by a modulator of the filter, an offset for an output of the integrator. ### Claim 19 (depends on 18) The method of claim 18, wherein the filter further comprises an encoder arranged to convert the offset and the output of the integrator from binary to thermometer code to produce the control signal. ### Claim 20 A circuit for producing an alternating signal, the circuit comprising: a voltage control circuit arranged to produce a control voltage; a frequency control circuit arranged to produce a control signal; and an oscillator arranged to produce an output signal with a frequency based on the control voltage and the control signal, wherein the frequency control circuit is further arranged to adjust the control signal such that the voltage control circuit adjusts the control voltage to be closer to an input voltage to the frequency control circuit.