# US 2025/0147713 A1 · Audio artifact reduction in universal audio jack (uaj) interface circuits > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0147713 A1 - Document ID: US20250147713A1 - Status: Published application - Kind: A1 - Application number: 18/500,224 - Filed: 2023-11-02 - Published: 2025-05-08 - Earliest claimed: 2023-11-02 - Assignees: Cirrus Logic International Semiconductor Ltd. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: Gaofeng Fan; Qi Cai; John B. Bowlerwell; Richard Turkson; Anindya Bhattacharya; Bhoodev Kumar - Web page: https://patentgrep.com/patent/US20250147713A1 ## CPC - G06F 3/162: {Interface to dedicated audio devices, e.g. audio drivers, interface to CODECs} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract Circuit techniques reduce or prevent audible artifacts in a Universal Audio Jack (UAJ) interface circuit, improving handling of mis-configuration/mis-attachment of devices. The interface includes at least one terminal for accepting an audio input signal or providing an audio line output signal coupled to an input or output of a first audio circuit. The first audio circuit operates from a low voltage domain and receives the audio input signal or provides the audio line output signal. A second circuit operates from a higher voltage domain and a switching circuit couples the at least one terminal to the second circuit. The output is slew-rate controlled to control a transition time of the output, so that audible artifacts in the audio input signal or the audio line output signal that could be generated by the switching circuit connecting the second circuit to the at least one terminal are avoided. ## Claims ### Claim 1 An audio interface circuit, comprising: at least one terminal for accepting an audio input signal or providing an audio line output signal; a first audio circuit having an input or an output coupled to the at least one terminal, wherein the first audio circuit is operated from a low voltage domain and receives the audio input signal as an input or provides the audio line output signal as an output; a second circuit operated from a high voltage domain having a voltage level greater than a voltage level of the low voltage domain; and a switching circuit that couples the at least one terminal to an output of the second circuit in response to a control signal, wherein the second circuit has an output that is slew-rate controlled to control a transition time of the output of the second circuit in response to the control signal, so that audible artifacts in the audio input signal or the audio line output signal that could be generated by the switching circuit connecting the second circuit to the at least one terminal are avoided. ### Claim 2 (depends on 1) The audio interface circuit, of claim 1, wherein the at least one terminal has a function selectable between at least one of an audio line input or audio output function for providing an audio line output signal or accepting an audio input signal, and between a microphone bias output function, wherein the first audio circuit is an audio input or line output circuit coupled to the at least one terminal for receiving the audio input signal or supplying the audio line output audio signal, wherein the second circuit is a microphone bias driver having an output that provides the microphone bias output level coupled to the at least one terminal. ### Claim 3 (depends on 2) The audio interface circuit of claim 2, wherein the function of the at least one terminal is selectable between all of the audio line output function, the microphone bias output function, and the audio input function. ### Claim 4 (depends on 2) The audio interface circuit of claim 2, wherein the switching circuit uses a switch protection bias voltage greater than or equal to a power supply voltage of the low voltage domain to protect switches of the switching circuit when the microphone bias driver is not coupled to the at least one terminal. ### Claim 5 (depends on 2) The audio interface circuit of claim 2, wherein the at least one terminal implements terminals of a universal audio jack (UAJ). ### Claim 6 (depends on 2) The audio interface circuit of claim 2, wherein the slew rate of the output of the microphone bias driver is independent of a load presented to the output of the microphone bias driver. ### Claim 7 (depends on 6) The audio interface circuit of claim 6, wherein the microphone bias driver comprises: an output driver for producing the output of the microphone bias driver; and a slew rate control circuit for receiving a reference input and providing a slew-rate-controlled output signal to an input of the output driver. ### Claim 8 (depends on 1) The audio interface circuit of claim 1, wherein the switching circuit uses a switch protection bias voltage greater than or equal to a power supply voltage of the low voltage domain to protect switches of the switching circuit. ### Claim 9 (depends on 1) The audio interface circuit of claim 1, wherein an audio output driver of the first audio circuit that provides the audio line output signal is designed to tolerate the voltage level of the high voltage domain. ### Claim 10 (depends on 1) The audio interface circuit of claim 1, wherein the switching circuit is designed to track the slew rate of the output of the second circuit. ### Claim 11 A method of preventing generation of audible artefacts by an audio interface circuit, comprising: accepting an audio input signal from or providing an audio line output signal to at least one terminal; operating a first audio circuit having an input or an output coupled to the at least one terminal from a low voltage domain; receiving the audio input signal as an input to the first audio circuit or providing the audio line output signal as an output from the first audio circuit; operating a second circuit from a high voltage domain having a voltage level greater than a voltage level of the low voltage domain; and selectively coupling the at least one terminal to an output of the second circuit in response to a control signal with a switching circuit; and controlling a slew-rate of an output of the second circuit to control a transition time of the output of the second circuit in response to the control signal, so that generation of the audible artifacts by the switching circuit connecting the second circuit to the at least one terminal is avoided. ### Claim 12 The method of 11, further comprising selecting a function of the at least one terminal between at least one of an audio line input or audio output function for providing an audio line output signal or accepting an audio input signal, and between a microphone bias output function, wherein the first audio circuit is an audio input or line output circuit coupled to the at least one terminal for receiving the audio input signal or supplying the audio line output audio signal, wherein the second circuit is a microphone bias driver having an output that provides the microphone bias output level coupled to the at least one terminal. ### Claim 13 (depends on 12) The method of claim 12, wherein the selecting of the function of the at least one terminal selects between all of the audio line output function, the microphone bias output function, and the audio input function. ### Claim 14 (depends on 12) The method of claim 12, further comprising protecting switches of the switching circuit when the microphone bias driver is not coupled to the at least one terminal by applying a switch protection bias voltage greater than or equal to a power supply voltage of the low voltage domain to the switches. ### Claim 15 (depends on 12) The method of claim 12, wherein the at least one terminal implements terminals of a universal audio jack (UAJ). ### Claim 16 (depends on 12) The method of claim 12, wherein the slew rate of the output of the microphone bias driver is independent of a load presented to the output of the microphone bias driver. ### Claim 17 (depends on 16) The method of claim 16, further comprising producing the output of the microphone bias driver from an output of the microphone bias driver; and receiving a reference input at a slew rate control circuit of the microphone bias driver; and providing a slew-rate-controlled output signal to an input of the output driver from the slew rate control circuit. ### Claim 18 (depends on 11) The method of claim 11, further comprising protecting switches of the switching circuit by applying a switch protection bias voltage greater than or equal to a power supply voltage of the low voltage domain to the switches. ### Claim 19 (depends on 11) The method of claim 11, wherein an audio output driver of the first audio circuit that provides the audio line output signal is designed to tolerate the voltage level of the high voltage domain. ### Claim 20 (depends on 11) The method of claim 11, wherein the switching circuit is designed to track the slew rate of the output of the second circuit.