High anti-interference audio input and output integrated circuit

Abstract

The utility model belongs to audio input output control circuit technical field, concretely relates to a kind of high anti-interference audio input output integrated circuit, including microphone input module and loudspeaker output module;The microphone input module and the loudspeaker output module are connected by whole piece ground copper foil;In the microphone input module, containing power filter unit VCC1V8_MICBIAS is connected in series with capacitor C22 ground through resistance R19, microphone signal is filtered after passing through capacitor C26, and is output to connector J1 pin through resistance R20 and resistance R21;In the loudspeaker output module, containing difference input positive pole SPK_P is connected in parallel with capacitor C27 and capacitor C30 through resistance R117, negative pole SPK_N is connected in parallel with capacitor C109 and capacitor C110 through resistance R118, and resistance R25 is connected in series between positive and negative channel.The utility model can solve the problem of sound quality degradation caused by high-frequency common-mode noise.

Description

Technical Field

[0001] This utility model belongs to the technical field of audio input / output control circuits, specifically relating to a high anti-interference audio input / output integrated circuit. Background Technology

[0002] With the development of artificial intelligence, AI technology has also been introduced into the toy manufacturing industry, which requires audio input / output circuits. Existing audio input / output circuits have the following technical defects: microphone power supplies lack high-frequency filtering, and the pickup signal is mixed with switching power supply noise; the speaker output has insufficient suppression of common-mode interference in the gigahertz frequency band; and the low impedance matching accuracy of differential signals leads to a decrease in the common-mode rejection ratio. To address these issues, this invention proposes an audio circuit that suppresses interference across the entire frequency band, solving the problem of sound quality degradation caused by high-frequency common-mode noise. Utility Model Content

[0003] The purpose of this invention is to provide a high anti-interference audio input / output integrated circuit that can solve the problem of sound quality degradation caused by high-frequency common-mode noise.

[0004] The specific technical solution adopted by this utility model is as follows:

[0005] A high-interference-resistant audio input / output integrated circuit includes a microphone input module and a speaker output module; the microphone input module and the speaker output module are connected by a single piece of grounded copper foil;

[0006] In the microphone input module, the power filter unit VCC1V8_MICBIAS is grounded through resistor R19 and capacitor C22. The microphone signal is filtered by capacitor C26 and then output to connector J1 pin through resistors R20 and R21.

[0007] The speaker output module includes a differential input positive terminal SPK_P connected in parallel with capacitors C27 and C30 via resistor R117, a negative terminal SPK_N connected in parallel with capacitors C109 and C110 via resistor R118, and a series resistor R25 between the positive and negative channels.

[0008] Preferably, in the microphone input module, the VCC1V8_MICBIAS power supply is grounded via a 100-ohm resistor R19 connected in series with a 4.7 microfarad capacitor C22. The microphone signal is filtered by a 10-picofarad capacitor C26, and the impedance is balanced by a 1-kiloohm resistor R20 and a resistor R21 before being output to the connector J1, model HC-1.25-3PWT for electromagnetic shielding.

[0009] Preferably, in the speaker output module, the SPK_P input is connected in series with a BLM18PG121SN1 common-mode choke and a 2.2 kΩ resistor R117; the SPK_N input is connected in series with a BLM18PG121SN1 common-mode choke and a 2.2 kΩ resistor R118; two stages of filter capacitors are connected in parallel: 22 nanofarads for filtering intermediate frequencies and 2.2 nanofarads for filtering high frequencies; a 3.3 kΩ bridging resistor R25 enhances common-mode rejection.

[0010] Preferably, capacitor C22 is an electrolytic capacitor with a capacitance error of ±20%; capacitor C26 is a ceramic capacitor with a capacitance accuracy of ±0.25 picofarads; and resistors R20 and R21 have a resistance matching error of ≤1% and are 0402 packaged metal film resistors.

[0011] Preferably, the power supply VCC1V8_MICBIAS is filtered by resistor R19 and capacitor C22 in sequence and then connected to the microphone bias; the microphone signal is coupled from MICIN_1P to connector J1 pin 1 via capacitor C26; connector J1 pin 2 is grounded through resistor R21, forming a differential loop impedance balance.

[0012] The metal shell of connector J1 is soldered to the PCB ground plane around its entire circumference; pins 4 and 5 are directly connected to the ground copper foil, and the shielding layer covers the signal trace area.

[0013] Preferably, the first-stage filtering is performed by capacitors C27 and C109, suppressing intermediate frequency interference from 100Hz to 20kHz; the second-stage filtering is performed by capacitors C30 and C110, suppressing high-frequency interference from 20kHz to 10MHz; capacitors C27, C109, C30, and C110 are all made of 0402 packaged X7R ceramic material; the capacitive reactance characteristics of capacitors C30 and C110 meet the following requirements: impedance ≤10 ohms at 10MHz frequency; equivalent series resistance of capacitor C22 ≤0.5 ohms.

[0014] Preferably, the power filter unit in the microphone input module has a cutoff frequency of 1.6Hz; the common-mode rejection unit in the microphone input module provides a rejection ratio of ≥40dB at a frequency of 1kHz; the two ground planes are connected by an array of vias with a via spacing of ≤2mm.

[0015] Preferably, a common-mode choke is added: a BLM18PG121SN1 choke with an impedance of 120 ohms @ 100MHz is connected in series at the SPK_P input terminal; a choke of the same model is connected in series at the SPK_N input terminal; the choke is installed at a distance of ≤ 1.5mm from resistors R117 and R118.

[0016] The technical effects achieved by this utility model are as follows:

[0017] This invention eliminates ground bounce noise and improves cross-module interference suppression rate by 30%; the microphone module covers 0.1Hz-50MHz, and the speaker module covers 100Hz-1GHz, with noise attenuation of >40dB across the entire frequency band; impedance matching error ≤1% ensures differential signal integrity; the connector is fully soldered with grounded copper foil, reducing radiated emissions to below Class B standards, ultimately solving the sound quality degradation problem caused by high-frequency common-mode noise. Attached Figure Description

[0018] Figure 1 This is the microphone input circuit in this utility model;

[0019] Figure 2 This is the speaker output circuit in this utility model. Detailed Implementation

[0020] To make the objectives and advantages of this utility model clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of this utility model and does not strictly limit the scope of protection specifically claimed by this utility model.

[0021] like Figure 1 as well as Figure 2 As shown, a high anti-interference audio input / output integrated circuit is characterized by comprising a microphone input module and a speaker output module; the microphone input module and the speaker output module are connected by a single piece of grounded copper foil.

[0022] In the microphone input module, the power filter unit VCC1V8_MICBIAS is grounded through resistor R19 and capacitor C22. The microphone signal is filtered by capacitor C26 and then output to connector J1 pin through resistors R20 and R21.

[0023] The speaker output module includes a differential input positive terminal SPK_P connected in parallel with capacitors C27 and C30 via resistor R117, a negative terminal SPK_N connected in parallel with capacitors C109 and C110 via resistor R118, and a series resistor R25 between the positive and negative channels.

[0024] In this invention, the microphone and speaker module are connected by a single piece of grounded copper foil, eliminating the potential difference between the two ground planes; blocking the common-mode noise propagation path, improving the signal-to-noise ratio by more than 15dB, and ensuring a unified audio signal transmission standard.

[0025] Preferably, in the microphone input module, the VCC1V8_MICBIAS power supply is grounded via a 100-ohm resistor R19 connected in series with a 4.7 microfarad capacitor C22. The microphone signal is filtered by a 10-picofarad capacitor C26, and the impedance is balanced by a 1-kiloohm resistor R20 and a resistor R21 before being output to the connector J1, model HC-1.25-3PWT for electromagnetic shielding.

[0026] In this invention, R19 and C22 form an RC low-pass filter, C26 filters out radio frequency interference, and R20 / R21 balance the differential impedance; the power supply ripple suppression rate is ≥90%@100Hz, the microphone channel has an anti-radio frequency interference capability of 50MHz, and the J1 full-circle welding shield attenuates electromagnetic radiation by 40dB.

[0027] Preferably, in the speaker output module, the SPK_P input is connected in series with a BLM18PG121SN1 common-mode choke and a 2.2 kΩ resistor R117; the SPK_N input is connected in series with a BLM18PG121SN1 common-mode choke and a 2.2 kΩ resistor R118; two stages of filter capacitors are connected in parallel: 22 nanofarads for filtering intermediate frequencies and 2.2 nanofarads for filtering high frequencies; a 3.3 kΩ bridging resistor R25 enhances common-mode rejection.

[0028] In this invention, a common-mode choke suppresses common-mode noise in the GHz band, and current-limiting resistors R117 / R118, together with C27 / C30 and C109 / C110, form a two-stage band-stop filter. The 1GHz common-mode interference attenuation is ≥40dB, the full-band harmonic distortion rate is ≤0.01%, and R25 improves the common-mode rejection ratio to 50dB.

[0029] Preferably, capacitor C22 is an electrolytic capacitor with a capacitance error of ±20%; capacitor C26 is a ceramic capacitor with a capacitance accuracy of ±0.25 picofarads; and resistors R20 and R21 have a resistance matching error of ≤1% and are 0402 packaged metal film resistors.

[0030] In this invention, electrolytic capacitor C22 filters low-frequency ripple, ceramic capacitor C26 eliminates high-frequency noise, and resistors R20 / R21 precisely match the differential impedance. The power supply noise suppression bandwidth covers 0.1Hz-1MHz, the impedance imbalance error is <0.5%, and microphone signal phase distortion is eliminated.

[0031] Preferably, the power supply VCC1V8_MICBIAS is filtered by resistor R19 and capacitor C22 in sequence and then connected to the microphone bias; the microphone signal is coupled from MICIN_1P to connector J1 pin 1 via capacitor C26; connector J1 pin 2 is grounded through resistor R21, forming a differential loop impedance balance.

[0032] The metal shell of connector J1 is soldered to the PCB ground plane around its entire circumference; pins 4 and 5 are directly connected to the ground copper foil, and the shielding layer covers the signal trace area.

[0033] In this invention, pin 1 and pin 2 are grounded to form a closed-loop circuit, and the metal casing is welded around the entire circumference to achieve electromagnetic shielding. The differential signal return path is shortened by 60%, the shielding layer suppresses 90% of external magnetic field coupling, and the channel crosstalk is reduced to -80dB.

[0034] Preferably, the first-stage filtering is performed by capacitors C27 and C109, suppressing intermediate frequency interference from 100Hz to 20kHz; the second-stage filtering is performed by capacitors C30 and C110, suppressing high-frequency interference from 20kHz to 10MHz; capacitors C27, C109, C30, and C110 are all made of 0402 packaged X7R ceramic material; the capacitive reactance characteristics of capacitors C30 and C110 meet the following requirements: impedance ≤10 ohms at 10MHz frequency; equivalent series resistance of capacitor C22 ≤0.5 ohms.

[0035] In this invention, C27 / C109 filters out interference in the human voice frequency band, C30 / C110 suppresses residual radio frequency noise, and X7R material ensures temperature stability. The noise attenuation slope from 20kHz to 10MHz is increased to 60dB / dec, the capacitive reactance at 10MHz is ≤5 ohms, and the parameter drift is <5% at an operating temperature of -40℃ to 125℃.

[0036] Preferably, the power filter unit in the microphone input module has a cutoff frequency of 1.6Hz; the common-mode rejection unit in the microphone input module provides a rejection ratio of ≥40dB at a frequency of 1kHz; the two ground planes are connected by an array of vias with a via spacing of ≤2mm.

[0037] In this invention, a 1.6Hz cutoff frequency filters out ultra-low frequency power fluctuations, array vias enhance the equipotential connection of the ground plane, microphone noise floor is reduced to 2μVrms, ground loop impedance is <5mΩ, and 1kHz common-mode rejection ratio exceeds 40dB.

[0038] Preferably, a common-mode choke is added: a BLM18PG121SN1 choke with an impedance of 120 ohms @ 100MHz is connected in series at the SPK_P input terminal; a choke of the same model is connected in series at the SPK_N input terminal; the choke is installed at a distance of ≤ 1.5mm from resistors R117 and R118.

[0039] In this invention, the choke is connected in series at the differential input terminal, and the 1.5mm spacing minimizes the lead inductance.

[0040] Insertion loss in the 100MHz-1GHz band is <0.2dB, ESD protection capability is improved to 8kV, and RF interference isolation is >100dB.

[0041] The working principle of this utility model is as follows: This utility model eliminates ground bounce noise and improves the cross-module interference suppression rate by 30%; the microphone module covers 0.1Hz-50MHz, the speaker module covers 100Hz-1GHz, and the noise attenuation of the entire frequency band is >40dB; the impedance matching error is ≤1%, ensuring the integrity of differential signals; the connector is fully soldered with grounded copper foil, and the radiated emission is reduced to below Class B standard.

[0042] The above description is merely a preferred embodiment of this utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model. Structures, devices, and operating methods not specifically described or explained in this utility model, unless otherwise specified or limited, shall be implemented using conventional methods in the field.

Claims

1. A high-EMI audio input / output integrated circuit, characterized by: It includes microphone input module and speaker output module; the microphone input module and the speaker output module are connected through whole piece ground copper foil; In the microphone input module, the power filter unit VCC1V8_MICBIAS is connected in series with the resistance R19 and the capacitor C22 to ground, and the microphone signal is filtered by the capacitor C26 and then output to the connector J1 pin through the resistance R20 and the resistance R21; In the speaker output module, the differential input positive SPK_P is connected in parallel with the capacitor C27 and the capacitor C30 through the resistance R117, and the negative SPK_N is connected in parallel with the capacitor C109 and the capacitor C110 through the resistance R118, and the resistance R25 is connected in series between the positive and negative channels.

2. The high anti-interference audio input and output integrated circuit according to claim 1, characterized in that: In the microphone input module, the VCC1V8_MICBIAS power supply is connected in series with the 100 ohm resistance R19 and the 4.7 microfarad capacitor C22 to ground, and the microphone signal is filtered by the 10 picofarad capacitor C26, balanced by the 1 kilohm resistance R20 and the resistance R21, and then output to the connector J1 type HC-1.25-3PWT to realize electromagnetic shielding.

3. The high anti-interference audio input and output integrated circuit according to claim 1, characterized in that: In the speaker output module, the SPK_P input is connected in series with the BLM18PG121SN1 common mode choke coil and the 2.2 kilohm resistance R117; the SPK_N input is connected in series with the BLM18PG121SN1 common mode choke coil and 2.2 kilohm resistance R118; two-stage filtering capacitors are connected in parallel: 22 nanofarad filter for medium frequency, 2.2 nanofarad filter for high frequency; the bridge resistance R25 with a resistance of 3.3 kilohms enhances common mode rejection.

4. The high anti-interference audio input and output integrated circuit according to claim 1, characterized in that: The capacitor C22 is an electrolytic capacitor with a capacity error of ±20%; the capacitor C26 is a ceramic capacitor with a capacity accuracy of ±0.25 picofarad; the resistances R20 and R21 have a resistance matching error of ≤1%, and are made of 0402 packaged metal film resistors.

5. The highly interference-resistant audio input / output integrated circuit of claim 1, wherein: The power supply VCC1V8_MICBIAS is filtered by the resistance R19 and the capacitor C22 in sequence and then connected to the microphone bias; the microphone signal is coupled to the connector J1 pin 1 by the MICIN_1P and the capacitor C26; the connector J1 pin 2 is grounded through the resistance R21, forming a differential loop impedance balance; The metal shell of the connector J1 is welded with the PCB ground plane all around; the pin 4 and the pin 5 are directly connected to the ground copper foil, and the shielding layer covers the signal trace area.

6. The highly interference-resistant audio input / output integrated circuit of claim 1, wherein: The first-stage filtering is undertaken by the capacitor C27 and the capacitor C109 to suppress 100Hz to 20kHz medium frequency interference; the second-stage filtering is undertaken by the capacitor C30 and the capacitor C110 to suppress 20kHz to 10MHz high frequency interference; the capacitors C27, C109, C30 and C110 are all made of 0402 packaged X7R ceramic material; the capacitive reactance characteristics of the capacitors C30 and C110 satisfy: the impedance is ≤10 ohms at 10MHz frequency; the equivalent series resistance of the capacitor C22 is ≤0.5 ohm.

7. The highly interference-resistant audio input / output integrated circuit of claim 1, wherein: The power filter unit in the microphone input module is set to have a cutoff frequency of 1.6Hz; the common mode rejection unit in the microphone input module provides a suppression ratio of ≥40dB at 1kHz frequency point; the two ground planes are connected through an array of vias with a via spacing of ≤2mm.

8. The highly interference-resistant audio input / output integrated circuit of claim 1, wherein: Addition of common mode choke: in series with BLM18PG121SN1 choke at SPK_P input, impedance 120 ohms @ 100 MHz; in series with the same type of choke at SPK_N input; Choke installation position from resistance R117 and resistance R118 ≤ 1.5 mm.

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