System and method for fast mode variation of digital microphones using digital crosstalk compensation

Abstract

The embodiments of this disclosure generally relate to systems and methods for rapid mode changes of a digital microphone using digital crosstalk compensation. One circuit includes a crosstalk compensation component and a subtractor. The crosstalk compensation component includes a power distribution reconstruction component and a reconstruction filter. The power distribution reconstruction component is configured to reconstruct the power distribution of a digital microphone coupled to a microelectromechanical (MEMS) device, wherein the power distribution represents the power consumption of the digital microphone over time between at least two operating modes of the digital microphone. The reconstruction filter is used to model the thermal and / or acoustic characteristics of the digital microphone. The subtractor has a first input for receiving a signal from the digital microphone, a second input coupled to the crosstalk compensation component, and an output for providing a digital output signal.

Description

Technical Field

[0001] The present invention generally relates to a system and method for rapid mode changes using a digital microphone with digital crosstalk compensation. Background Technology

[0002] Digital microphones typically include microelectromechanical systems (MEMS) devices that receive ambient sound waves or lower-frequency pressure waves in the audio band and convert them into analog signals. Digital microphones also include analog-to-digital converters (ADCs) for converting analog signals to digital signals, as well as other digital processing components. Digital microphones may include the ability to switch between different operating modes in response to control signals, such as between a higher quality mode with high signal-to-noise ratio (SNR) and high power dissipation and a lower quality mode with low SNR and low power dissipation. Future generations of digital microphones may require the flexibility to switch between higher and lower quality modes, for example, through the use of dynamic SNR adjustment or dynamic power-saving strategies. Future generations of digital microphones may also require the ability to perform dynamic adjustment quickly and seamlessly by minimizing audible switching artifacts. Audible switching artifacts at the output of a digital microphone may be referred to as, and are specified herein, "crosstalk," "X-talk," or "XT." Summary of the Invention

[0003] According to one embodiment, a circuit includes a crosstalk compensation component and a subtractor. The crosstalk compensation component includes a power distribution reconstruction component and a reconstruction filter. The power distribution reconstruction component is configured to reconstruct the power distribution of a digital microphone communicating with a microelectromechanical (MEMS) device, wherein the power distribution represents the power consumption of the digital microphone over time between at least two operating modes of the digital microphone. The reconstruction filter is configured to model the thermal and / or acoustic characteristics of the digital microphone. The subtractor has a first input configured to receive a signal from the digital microphone, a second input coupled to the crosstalk compensation component, and an output configured to provide a digital output signal.

[0004] According to one embodiment, a digital microphone includes: a microelectromechanical system (MEMS) device configured to provide an analog input signal; a front-end circuit of the MEMS device; an analog-to-digital converter (ADC) coupled to the front-end circuit; a first digital filter coupled to the ADC, wherein at least one of the front-end circuit, the ADC, and the first digital filter includes a power distribution; a power measurement component configured to measure the power or current of at least one of the front-end circuit, the ADC, and the first digital filter; a power distribution reconstruction component communicating with the power measurement component; a reconstruction filter configured to model the thermal and / or acoustic characteristics of the digital microphone, wherein the reconstruction filter communicates with the power distribution reconstruction component; and a subtractor having a first input coupled to the first digital filter, a second input coupled to the reconstruction filter, and an output configured to provide a digital output signal corresponding to the analog input signal.

[0005] According to one embodiment, a method of operating a digital microphone includes: converting an analog input signal from a microelectromechanical (MEMS) device using an analog-to-digital converter (ADC) in the digital microphone, wherein the ADC includes a power distribution representing the power consumption of the ADC as a function of time when switching between a first operating mode and a second operating mode; reconstructing the power distribution; using the reconstructed power distribution to determine a crosstalk estimate of the digital microphone; and subtracting the crosstalk estimate from the output signal of the ADC to generate a digital output signal corresponding to the analog input signal. Attached Figure Description

[0006] To gain a more complete understanding of the invention and its advantages, the following description is now given in conjunction with the accompanying drawings, in which:

[0007] Figure 1 This is a block diagram of an exemplary digital microphone with an internal clock-changing component;

[0008] Figure 2 yes Figure 1 Timing diagram of the power distribution of the digital microphone;

[0009] Figure 3 This is a block diagram of a digital microphone with X-talk compensation inside a digital microphone package according to one embodiment;

[0010] Figure 4 This is a block diagram of a digital microphone with X-talk compensation outside a digital microphone package according to one embodiment;

[0011] Figure 5 This is a block diagram of a digital microphone that performs X-talk compensation using measured power dissipation variation information according to one embodiment;

[0012] Figure 6 It is according to one embodiment for measurement Figure 5 A schematic diagram of a power measurement circuit for power dissipation variations in a digital microphone;

[0013] Figure 7 Is Figure 3 , Figure 4 or Figure 5 A block diagram of the reconstruction filters used in any of the digital microphones;

[0014] Figure 8 This is a timing diagram of the X-talk voltage for different switching transitions relative to a digital microphone, with a power variation of 300μW.

[0015] Figure 9 This is a timing diagram of the X-talk voltage for a step switching transition according to one embodiment and the residual error after applying X-talk compensation;

[0016] Figure 10 This is a block diagram of a method for operating a digital microphone including X-talk compensation according to one embodiment; and

[0017] Figure 11 This is a block diagram of a digital microphone system according to one embodiment. Detailed Implementation

[0018] The manufacture and use of the presently preferred embodiments are discussed in detail below. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways of making and using the invention and do not limit the scope of the invention.

[0019] While current digital microphones offer the ability to switch between higher and lower quality modes, future generations of digital microphones may require greater flexibility in this switching, for example, through the use of dynamic SNR adjustment or dynamic power-saving strategies. Future generations of digital microphones may also need to perform dynamic adjustment quickly and seamlessly by minimizing audible switching artifacts. The audible switching artifact at the output of a digital microphone may be referred to as, and is specified herein, as “crosstalk,” “X-talk,” or “XT.”

[0020] The embodiments described herein reconstruct and subtract X-talk interference noise in a digital microphone to address various power distribution variations caused by changes in operating mode. In this way, audible artifacts in the digital microphone output resulting from changes in operating mode are significantly reduced below the audible threshold. As described herein, the term "power distribution" refers to the power dissipation of a digital microphone over time, particularly during the time interval between transitions between two or more operating modes of the digital microphone.

[0021] In some embodiments, the performance of a digital microphone is varied based on control signals and power distribution at the left and right (L / R) pins of the digital microphone. This typically occurs between a lower power / lower performance operating mode and a higher power / higher performance operating mode. Various methods for changing the operating mode of a digital microphone are known. For example, the bias current or clock frequency of the digital microphone can be changed, or the value of the sampling capacitor inside the digital microphone's ADC can be changed. Furthermore, changes in the operating mode of the digital microphone result in changes in power, which in some cases can lead to audible acoustic artifacts. For example, if the clock frequency changes from F... S Change to F S / 2, and the power consumption of the digital microphone typically changes by about 300 μW. In the reconstruction path, according to an embodiment, the power distribution associated with this power consumption change is applied as input to a first reconstruction filter that models the dynamic characteristics of the temperature time constant of the MEMS device, and a second reconstruction filter that models the acoustic high-pass frequency response of the MEMS device. In one embodiment, the first reconstruction filter comprises a second-order digital filter, and the second reconstruction filter comprises a first-order digital filter. The reconstructed thermoacoustic X-talk is then subtracted from the main signal path in the digital microphone, thereby significantly reducing audible artifacts in the output of the digital microphone. In some embodiments, a reduction below the audible threshold is achieved. In other embodiments, if only a partially compensated operating mode is required, only a portion of the reconstructed thermoacoustic X-talk is subtracted from the main signal path.

[0022] exist Figure 1 The block diagram depicts a digital microphone 100 with dynamically changing internal clock. The digital microphone 100 includes a MEMS device 102 for converting ambient sound waves and pressure waves into analog signals. The analog signals are received by an application-specific integrated circuit (ASIC) 104. The ASIC 104 includes an ADC 106, which converts the analog signals from the MEMS device 102 into digital signals for further digital signal processing. Figure 1In the digital microphone 100, repeater 108 is coupled to the output of ADC 106, digital filter 110 is coupled to the output of repeater 108, and digital modulator 112 is coupled to the output of digital filter 110 to provide a one-bit digital output signal at output bus 114. The digital microphone 100 receives a clock (clk) signal at node 124, which is received directly at an input by multiplexer 118 and indirectly at another input via clock divider 120. The output of multiplexer 118 provides the clock signal and a divided version of the clock signal at output 116, which is then received by ADC 106. Multiplexer 118, clock divider 120, and repeater 108 are all controlled by control signal (ctrl) 122.

[0023] To achieve flexibility in terms of performance (SNR) and / or power consumption, different clock rates can be used based on a constant incoming clock rate (clk) generated by clock divider 120. Due to the action of repeater 108, which interpolates by a factor D under the control of ctrl control signal 122, the range of different clock rates can be from a reduced internal clock rate (clkred = clk / D) to a high clock rate. Figure 1 The digital microphone 100 shown is disclosed in co-pending U.S. Patent Applications Nos. 16 / 773,079 and 16 / 871,546, both entitled “Configurable Microphone using Interval Clock Changing”, and both of which are incorporated herein by reference in their entirety.

[0024] Another strategy to achieve flexibility in terms of performance (SNR) and / or power consumption in one or more operating modes is to change the sampling capacitor of the ADC in the digital microphone.

[0025] exist Figure 2 In the middle, it is described Figure 1 The timing diagram 200 shows the power distribution of the internal clock of the digital microphone 100 over time. Timing diagram 200 includes the timing waveform 206 of the digital microphone's selection pin over time. Figure 2 In the middle, the digital microphone 100 receives signals from a clock frequency F at full rate. S The higher performance operating mode is switched to one with a half-rate clock frequency F. S The lower-performance operating mode of / 2 is then switched back to the full-rate clock frequency F. S A higher performance operating mode. As shown in clock timing bar 204, the transition of the falling edge of the selection pin waveform 206 is related to the change from F. S Clock rate to F SThe transition at the / 2 clock rate is simultaneous. However, the transition of the subsequent rising edge of the select pin waveform 206 is simultaneous with the transition from F... S / 2 clock rate to F S The clock rate transitions are not simultaneous. Due to the ramp change in the internal bias current of the digital microphone 100, the transition to F... S There is a lag in the clock rate transition, as explained in further detail below. Timing diagram 200 also shows the power consumption over time. The power distribution 202 is at its maximum between time t0 and time t1, drops to a lower power consumption between time t1 and time t2, and remains at a lower power consumption between time t2 and time t3. The difference between the maximum power consumption and the lower power consumption is... Figure 2 This is shown as "ΔμW" 208, and in the embodiment it is approximately 300μW. The power distribution ramps up to full power consumption between time t3 and time t4, and returns to full power consumption between time t4 and time t5. Figure 2 As shown in the timing diagram, when the clock frequency changes from F... S Change to F S At / 2, the dynamic power change at time t1 is negative, while when the clock frequency changes from F... S / 2 reverts to F S At time t4, the dynamic power change is positive.

[0026] Therefore, when the internal clock changes, the dynamic current (power) changes immediately and should be compensated for to avoid audible artifacts due to thermoacoustic crosstalk. To reduce spikes in dissipated power, the internal clock frequency is adjusted from F... S Change to F S In the case of / 2, the bias current decreases slowly (ramp) to avoid such audible artifacts. As mentioned above, from F S / 2 becomes F S In the same case, the same slope strategy can be applied.

[0027] The same ramp power distribution can be followed when changing the sampling capacitor to achieve different operating modes in a digital microphone.

[0028] While using a slow ramp can reduce or even eliminate audible artifacts, the corresponding transitions between desired operating modes of a digital microphone will be slow. To effectively reduce audible artifacts, in some cases, the internal power ramp can exceed hundreds of milliseconds. However, in many applications, it is desirable to achieve transitions between operating modes of a digital microphone as quickly as possible without generating audible artifacts.

[0029] Embodiments of digital noise compensation systems and methods are shown and described in more detail below to significantly reduce audible artifacts in digital microphones while allowing rapid switching between operating modes of the digital microphones.

[0030] Figure 3 This is a block diagram of a digital microphone 300 with X-talk compensation within a digital microphone package according to one embodiment. The digital microphone 300 includes a MEMS device 302 coupled to an ASIC 304. In one embodiment, the ASIC 304 includes analog front-end circuitry 306, such as a source follower circuit coupled to an ADC 308. In one embodiment, the ADC 308 includes a voltage-controlled oscillator ADC (VCO ADC) coupled to a digital low-pass filter 310. The MEMS device 302 and the ASIC 304, together with the modulator 314 described further in detail below, constitute the core components or circuitry of the main signal path of the digital microphone 300. In embodiments, if a switched-capacitor Σ-Δ ADC or a VCO ADC is used, the source follower circuitry can be used independently.

[0031] exist Figure 3 In the digital microphone 300, an external command above the L / R pin or an input at node 318 is used to initialize dynamic distribution changes. Based on this command, internal information is derived by the "control signal generation" component 320 to adapt to the configuration of the digital microphone 300 (to implement internal clock changes or sampling capacitor changes), which in turn causes a change in the power distribution "P" and thus results in X-talk. A first internal control signal 322A is therefore used to control the internal clock changes or sampling capacitor changes and is received by the ASIC 304 as shown.

[0032] According to an embodiment, to compensate for X-talk, a digital estimation is performed by the X-talk compensation component 325, which may also be referred to as a “reconstruction path.” In one embodiment, the X-talk compensation component receives a copy 322B of a first internal control signal. The X-talk compensation component 325 includes a power distribution reconstruction component 324 (for reconstructing the power distribution “P” and generating a reconstructed power distribution “P*”) and a reconstruction filter 326 (for reconstructing the thermal and acoustic characteristics of X-talk originating from the digital microphone 300). To model the thermal / acoustic characteristics, ideally all thermal / acoustic characteristics of the entire digital microphone assembly are considered. For example, the volume of the ASIC 304, the thermal contact of the ASIC 304 with the surrounding environment, the package size(s) of the digital microphone 300, the thermal sensitivity of the MEMS device 302, the amount of packaging used to package the ASIC 302 (e.g., “glob-top”), and many other thermal and acoustic characteristics can be considered to achieve accurate X-talk estimation.

[0033] The output signal of the X-talk compensation component 325 is subtracted from the main digital signal path of the digital microphone 300. Therefore, the output digital filter 310 in the ASIC 304 is received by the first input of the subtractor 312, and the output of the X-talk compensation component 325 is received by the second input of the subtractor 312. According to an embodiment, the output of the subtractor 312 is received by the modulator 314 to generate a one-bit pulse modulation density (PDM) signal at the digital output bus 316.

[0034] The power reconstruction curve 324 includes digital or analog components for reconstructing the power distribution of a digital microphone using direct power or current measurements, as explained in further detail below, particularly regarding... Figure 5 and Figure 6 .

[0035] The reconstruction filter 326 is described in more detail below, especially regarding Figure 7 Further details regarding the reconstruction filter 326 can be found in U.S. Patent No. 10,491,996, entitled "Micro-Electro-Mechanical System (MEMS) Circuit and Method for Reconstructing an Interference Variable," which is incorporated herein by reference in its entirety. Additional details regarding the reconstruction filter 326 can also be found in U.S. Patent No. 10,244,315, entitled "Circuit Arrangement with an Optimized Frequency Response and Method for Calibrating a Circuit Arrangement," which is incorporated herein by reference in its entirety.

[0036] exist Figure 3 In one embodiment, the X-talk compensation component 325 may be integrated together with the ASIC 304 in a single integrated circuit. In other embodiments, the X-talk compensation component 325 may be integrated on a first integrated circuit, while the ASIC 304 may be integrated on a second integrated circuit. According to embodiments, both the first and second integrated circuits may be packaged together in a single semiconductor package. In embodiments, other packaging implementations may be used. Figure 3 The various components shown can be implemented as hardware components such as discrete or integrated circuits, or as software components containing instructions stored in memory and implemented by a microprocessor. Figure 3 Not shown in the image, but... Figure 11(Best illustrated herein, and described in more detail below). According to embodiments, any suitable mix of hardware and software components may be used. In various embodiments, the hardware components may include integrated circuits or discrete circuit components.

[0037] According to an embodiment, the reconstruction of X-talk can also be implemented outside the package of the digital microphone, such as... Figure 4 As shown. Figure 4 A digital microphone 400 is illustrated, in which a MEMS device 302, an ASIC 304 including front-end circuitry 306, an ADC 308, a digital filter 310, a modulator 314, and a control signal assembly 320 are implemented in a first semiconductor package 402. An X-talk compensation assembly 325 including a power distribution reconstruction assembly 324 and a reconstruction filter 326, and a subtractor 312 are implemented in a second semiconductor package 404. In an embodiment, the first semiconductor package 402 and the second semiconductor package 404 can be implemented on a single substrate such as a printed circuit board (PCB). The control signal at node 318 is provided by… Figure 4 The first semiconductor package 402 and the second semiconductor package 404 in the implementation receive the signal. The PDM signal generated by the modulator 314 in the first semiconductor package 402 is received by the input of the subtractor 312 in the second semiconductor package 404. All other signals and components are essentially as described above. Figure 3 The digital microphone 300 described herein. In an embodiment, the assembled first semiconductor package 402 may be supplied by the digital microphone manufacturer, and the assembled second semiconductor package 404 may be supplied by the digital microphone customer.

[0038] If the dynamic changes in the power distribution (SNR and power) are applied, the reconstruction of the power distribution can also be based on measurements (e.g., measurements of the bias current that define the power consumption of a digital microphone), such as... Figure 5 The digital microphone 500 is shown in the diagram. The digital microphone 500 includes a MEMS device 302, an ASIC 304 including front-end circuitry 306, an ADC 308, a digital filter 310, a subtractor 312, a modulator 314, a control signal generation component 320, and an X-talk compensation component 325 including a power distribution reconstruction component 324 and a reconstruction filter 326, all of which are located in the front end. Figure 3 The digital microphone 300 is described and shown. However, the digital microphone 500 also includes a power change measurement component 502, which has an input coupled to a power supply terminal of the ASIC 304 and an output coupled to an input of the X-talk compensation component 325. In one embodiment, the power change measurement component 502 does not need to receive a control signal and can provide continuous power change measurement.

[0039] Figure 6It is according to one embodiment for measurement Figure 5 A schematic diagram of a power measurement circuit 600 for power dissipation variations or bias current variations in a digital microphone 500. According to one embodiment, power dissipation over time can be measured by using a low-dropout regulator (LDO) connected in series with the power supply terminals of the digital microphone and measuring the current of the LDO using a replication circuit. In this embodiment, the power measurement circuit can be designed relatively simply to save on integrated circuit size and cost.

[0040] In one embodiment, the power measurement circuit 600 therefore includes an LDO voltage regulator 602 coupled to a current sensor 604. The LDO 602 is coupled at node 610 to a power supply terminal of an ASIC functional building block 606, which may represent the functional block of the previously shown and described ASIC 304, or include more or fewer functional blocks. The LDO 602 includes a power supply coupled to V... REF The LDO 602 includes a reference voltage input from a reference voltage source and a current input coupled at node 610 to the power supply node of the ASIC functional building block 606. The LDO 602 includes an operational amplifier 608, which has a current input for receiving V... REF The LDO 602 includes a first input of a reference voltage, a second input coupled to node 610, and an output. It also includes a MOS transistor M1, through which the current flowing is specified as I. SUPP It is the power supply current of block 606 built through ASIC functionality. The gate of transistor M1 is coupled to the output of the operational amplifier, and the current path of transistor M1 is coupled to the power supply voltage V. SUP Between node 610 and the power measurement circuit 600, the current sensor 604 is also included, wherein the current sensor includes a MOS transistor M1C and a sensing resistor 612 coupled to the source of the MOS transistor M1C at the output node 614. In one embodiment, the sensing resistor 612 may also be coupled to ground. The gate of the MOS transistor M1C is coupled to the gate of the MOS transistor M1. The current path of the MOS transistor M1C is coupled to the source of the power supply voltage I. SUPP_COPY Between output node 614 and output node 614. Therefore, the voltage at output node 614 is a continuous measure of the power dissipation of the ASIC functional building block 606 and generates a copy of the P* power distribution.

[0041] Figure 7 Is Figure 3 , Figure 4 or Figure 5A block diagram of a reconstruction filter 326 used in any of the digital microphones. Reconstruction filter 326 receives a copy of the P* power distribution as input signal 702 to gain stage 704. The output of gain stage 704 is coupled to a first digital filter 706. The output of the first digital filter 706 is coupled to a second digital filter 708. The output of the second digital filter 708 provides a digital X-talk estimate 710.

[0042] The thermal behavior of MEMS device 302 is modeled by the first digital filter 706 using a second-order digital infinite impulse response (IIR) filter (thermal model). The acoustic high-pass behavior of MEMS device 302 is modeled by the second digital filter 708 using a first-order high-pass digital filter. The input signal P* is an estimated power variation (replica power distribution) due to the dynamic pattern changes of the digital microphone being used. Gain stage 704, first digital filter 706, and second digital filter 708 can be implemented as, for example, digital circuitry in an integrated circuit, or by combining software instructions stored in memory with a microprocessor.

[0043] The interference noise generated by the digital microphone varies depending on the size and shape of the MEMS device 302. Therefore, subtracting the same compensation signal from the main signal path of the digital microphone will not adequately compensate for the interference noise. To adapt to the varying interference signal, the reconstruction filter 326 is advantageously implemented as an adaptive filter by adapting to the varying interference signal.

[0044] Figure 8 This is a timing diagram 800 of the analog XT voltage for different switching transitions relative to a digital microphone with a power change of 300μW. The power change of the digital microphone is performed at different transition rates, including a slow ramp (0.3 seconds), a medium ramp (between 0.1 seconds and 0.02 seconds), and a high-speed step. Figure 8 The diagram also shows a seamless threshold voltage below which the XT signal is inaudible.

[0045] Figure 8 An X-talk response 802 for a step transition reaching a peak of about 0.8 mV, an X-talk response 808 for a 0.2-second ramp transition reaching a peak of about 0.7 mV, and an X-talk response 806 for a 0.1-second ramp transition reaching a peak of about 0.3 mV are shown in one embodiment, all of which exceed a seamless threshold 810 of 0.2 mV. Figure 8 The X-talk response 804 for a 0.3-second ramp transition with a peak of approximately 0.1 mV is also shown, which is below the threshold of the seamless threshold 810.

[0046] exist Figure 8As can be observed, the faster the change between operating modes of a digital microphone, the larger the corresponding X-talk artifact value. Typically, a slow ramp is used in digital microphones to reduce the amplitude of the artifacts, thus keeping them below the audible threshold.

[0047] Figure 9 This is a timing diagram 900 of the X-talk voltage for a step transition according to one embodiment, and the residual error after applying X-talk compensation. Specifically, the reconstructed X-talk response 902 to the step transition is shown, also reaching a value of approximately 0.8 mV, far exceeding the 0.2 mV value of the seamless threshold 906. The reconstructed X-talk response 902 is subtracted from the main signal path during the step transition to provide a compensated output signal as previously described. Figure 9 The figure depicts the worst-case (step transition) residual X-talk value of 904 (after compensation). The compensated output signal has almost no residual X-talk and decreases to even much lower than [the value is missing here]. Figure 8 The slow slope situation shown (assuming it is inaudible).

[0048] Figure 10 This is a block diagram of a method 1000 for operating a digital microphone including X-talk compensation according to one embodiment. Method 1000 includes: in step 1002, converting an analog input signal from a microelectromechanical (MEMS) device using an analog-to-digital converter (ADC) in the digital microphone, wherein the ADC includes a power distribution representing the power consumption of the ADC as a function of time when switching between a first operating mode and a second operating mode; in step 1004, reconstructing the power distribution; in step 1006, determining a crosstalk estimate for the digital microphone using the reconstructed power distribution; and in step 1008, subtracting the crosstalk estimate from the output signal of the ADC to generate a digital output signal corresponding to the analog input signal.

[0049] Figure 11This is a block diagram of a digital microphone system 1100 according to one embodiment. The digital microphone system 1100 includes a MEMS device 1102 having an analog output 1104 coupled to a digital microphone 1106, which communicates with a microprocessor 1110 via a digital bus 1108 to transmit control signals and output signals. The digital microphone 1106 may include any of the digital microphone embodiments described above. The microprocessor 1110 communicates with a memory 1120 via a digital bus 1116 to receive stored commands and store data. Any suitable microprocessor or other processor and any suitable type of memory can be used. The digital microphone system 1100 may also include other components 1118, such as other analog or digital circuitry or components, such as filters, or other analog or digital circuitry systems specific to various product applications. The digital microphone system 1100 is merely an example of a type of system that may include the digital microphone described herein, and many other such digital microphone systems are possible while still containing the embodiment concepts.

[0050] According to embodiments, a system and method for reconstructing and subtracting X-talk interference noise from the main signal path of a digital microphone to provide a digital output signal with very low or inaudible X-talk has been described. Interference noise may occur due to changes in power distribution during changes in the operating mode of the digital microphone.

[0051] Compared to existing solutions, the advantages are that power changes and corresponding changes in operating modes can be performed faster and any overhead analog circuitry (e.g., digital-to-analog converters) can be eliminated.

[0052] Example 1. According to one embodiment, a circuit includes: a crosstalk compensation component including a power distribution reconstruction component and a reconstruction filter, the power distribution reconstruction component being configured to reconstruct the power distribution of a digital microphone communicating with a microelectromechanical (MEMS) device, wherein the power distribution represents the power consumption of the digital microphone over time between at least two operating modes of the digital microphone, the reconstruction filter being configured to model the thermal and / or acoustic characteristics of the digital microphone; and a subtractor having a first input configured to receive a signal from the digital microphone, a second input coupled to the crosstalk compensation component, and an output configured to provide a digital output signal.

[0053] Example 2. The circuit according to Example 1, wherein the reconstruction filter includes an input configured to receive the reconstructed power distribution.

[0054] Example 3. A circuit according to any of the examples above, wherein the power distribution reconstruction component includes a power change measurement component configured to measure the power distribution of a digital microphone.

[0055] Example 4. A digital microphone according to any of the examples above, wherein the reconstruction filter includes a gain stage, a first digital filter, and a second digital filter, the first digital filter being configured to model the thermal characteristics of the digital microphone, and the second digital filter being configured to model the acoustic characteristics of the digital microphone.

[0056] Example 5. A digital microphone according to any of the examples above, wherein the first digital filter includes a second-order digital filter.

[0057] Example 6. A circuit based on any of the examples above, wherein the second digital filter comprises a first-order digital filter.

[0058] Example 7. A digital microphone according to any of the examples above, wherein the digital microphone, crosstalk compensation component, and subtractor are packaged together in a semiconductor package.

[0059] Example 8. A digital microphone according to any of the examples above, wherein the crosstalk compensation component and the subtractor are outside the semiconductor package of the digital microphone.

[0060] Example 9. According to one embodiment, a digital microphone includes: a microelectromechanical system (MEMS) device configured to provide an analog input signal; front-end circuitry coupled to the MEMS device; an analog-to-digital converter (ADC) coupled to the front-end circuitry; a first digital filter coupled to the ADC, wherein at least one of the front-end circuitry, the ADC, and the first digital filter includes a power distribution; a power measurement component configured to measure power or current in the front-end circuitry, the ADC, and the first digital filter; a power distribution reconstruction component in communication with the power measurement component; a reconstruction filter configured to model the thermal and / or acoustic characteristics of the digital microphone, wherein the reconstruction filter in communication with the power distribution reconstruction component; and a subtractor having a first input coupled to the first digital filter, a second input coupled to the reconstruction filter, and an output configured to provide a digital output signal corresponding to the analog input signal.

[0061] Example 10. A digital microphone according to Example 9, wherein the power measurement component includes a voltage regulator coupled to a current sensor.

[0062] Example 11. A digital microphone according to any of the examples above, wherein the voltage regulator includes a low-dropout voltage regulator having a reference voltage input and a current input, the current input being coupled to a power supply node of a front-end circuit, an ADC, and a first digital filter.

[0063] Example 12. A digital microphone according to any of the examples above, wherein the current sensor includes a transistor and a sensing resistor coupled to the source of the transistor.

[0064] Example 13. A digital microphone according to any of the examples above, wherein the front-end circuitry, ADC, first digital filter, power distribution reconstruction component, power measurement component, reconstruction filter and subtractor are packaged together in a semiconductor package.

[0065] Example 14. A digital microphone according to any of the examples above, further comprising a left / right (L / R) input coupled to the digital microphone and a control signal generation component coupled to the ADC.

[0066] Example 15. A digital microphone according to any of the above examples further includes a modulator having an input coupled to the output of a subtractor and an output configured to provide a pulse modulation density (PDM) signal.

[0067] Example 16. According to one embodiment, a method of operating a digital microphone includes: converting an analog input signal from a microelectromechanical (MEMS) device using an analog-to-digital converter (ADC) in the digital microphone, wherein the digital microphone includes a power distribution representing the power consumption of the digital microphone as a function of time when switching between a first operating mode and a second operating mode; reconstructing the power distribution; using the reconstructed power distribution to determine a crosstalk estimate of the digital microphone; and subtracting the crosstalk estimate from the output signal of the ADC to generate a digital output signal corresponding to the analog input signal.

[0068] Example 17. According to the method of Example 16, wherein reconstructing the power distribution includes measuring the power or current of the digital microphone.

[0069] Example 18. A method according to any of the examples above, wherein determining the crosstalk estimate of the digital microphone includes digital filtering of the reconstructed power distribution.

[0070] Example 19. The method according to any of the above examples, wherein digital filtering of the reconstructed power distribution includes digital filtering of the reconstructed power distribution using a thermal model of the MEMS device.

[0071] Example 20. The method according to any of the above examples, wherein digital filtering of the reconstructed power distribution includes digital filtering of the reconstructed power distribution using an acoustic model of a MEMS device.

[0072] Although the invention has been described with reference to illustrative embodiments, this specification is not intended to be limited in meaning. By referring to this specification, those skilled in the art will clearly understand various modifications and combinations of the illustrative embodiments and other embodiments of the invention. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A circuit comprising: A crosstalk compensation component includes a power distribution reconstruction component and a reconstruction filter. The power distribution reconstruction component is configured to reconstruct the power distribution of a digital microphone including a microelectromechanical system (MEMS) device, wherein the power distribution represents the power consumption of the digital microphone over time between at least two operating modes of the digital microphone. The reconstruction filter is configured to receive the reconstructed power distribution and model the thermal and / or acoustic characteristics of the digital microphone to provide a crosstalk estimate. as well as The subtractor has a first input configured to receive a signal from the digital microphone, a second input coupled to the crosstalk compensation component to receive the crosstalk estimate, and an output configured to provide a digital output signal by subtracting the crosstalk estimate from the signal.

2. The circuit of claim 1, wherein the power distribution reconstruction component is configured to receive a signal from the power measurement component for reconstructing the power distribution of the digital microphone.

3. The circuit of claim 1, wherein the reconstruction filter comprises a gain stage, a first digital filter, and a second digital filter, the first digital filter being configured to model the thermal characteristics of the digital microphone, and the second digital filter being configured to model the acoustic characteristics of the digital microphone.

4. The circuit according to claim 3, wherein the first digital filter comprises a second-order digital filter.

5. The circuit according to claim 3, wherein the second digital filter comprises a first-order digital filter.

6. The circuit of claim 1, wherein the crosstalk compensation component and the subtractor are packaged together in a semiconductor package.

7. The circuit of claim 1, wherein the crosstalk compensation component and the subtractor are external to the semiconductor package of the digital microphone.

8. A digital microphone, comprising: Microelectromechanical systems (MEMS) devices are configured to provide analog input signals; Front-end circuitry, coupled to the MEMS device; An analog-to-digital converter (ADC) is coupled to the front-end circuit. An output digital filter is coupled to the ADC, wherein at least one of the front-end circuitry, the ADC, and the output digital filter includes a power distribution; A power measurement component is configured to measure the power and / or current of at least one of the front-end circuit, the ADC, and the output digital filter; A power distribution reconstruction component communicates with the power measurement component; A reconstruction filter is configured to model the thermal and / or acoustic characteristics of the digital microphone, wherein the reconstruction filter communicates with the power distribution reconstruction component; as well as The subtractor has a first input coupled to the output digital filter, a second input coupled to the reconstruction filter, and an output configured to provide a digital output signal corresponding to the analog input signal. The power distribution reconstruction component is configured to reconstruct the power distribution based on a signal from the power measurement component, the power distribution being used to determine a crosstalk estimate for the digital microphone, wherein the crosstalk estimate is subtracted from the output signal of the output digital filter to provide the digital output signal.

9. The digital microphone of claim 8, wherein the power measurement component includes a voltage regulator coupled to a current sensor.

10. The digital microphone of claim 9, wherein the voltage regulator comprises a low-dropout voltage regulator having a reference voltage input and a current input, the current input being coupled to a power supply node of the front-end circuit, the ADC, and the output digital filter.

11. The digital microphone of claim 9, wherein the current sensor comprises a transistor and a sensing resistor coupled to the source of the transistor.

12. The digital microphone of claim 8, wherein the front-end circuitry, the ADC, the output digital filter, the power distribution reconstruction component, the power measurement component, the reconstruction filter, and the subtractor are packaged together in a semiconductor package.

13. The digital microphone of claim 8, further comprising a left / right input coupled to the digital microphone and a control signal generation component coupled to the ADC.

14. The digital microphone of claim 8, further comprising a modulator having an input coupled to the output of the subtractor and an output configured to provide a pulse density modulated signal.

15. A method of operating a digital microphone, the method comprising: The analog input signal from the microelectromechanical system (MEMS) device is converted using an analog-to-digital converter (ADC) in the digital microphone, wherein the digital microphone includes a power distribution that represents the power consumption of the digital microphone as a function of time when switching between a first operating mode and a second operating mode. Reconstruct the power distribution; The crosstalk estimate of the digital microphone is determined using the reconstructed power distribution; as well as The crosstalk estimate is subtracted from the output signal of the ADC to generate a digital output signal corresponding to the analog input signal.

16. The method of claim 15, wherein reconstructing the power distribution includes measuring the power or current of the digital microphone.

17. The method of claim 15, wherein determining the crosstalk estimate of the digital microphone comprises digitally filtering the reconstructed power distribution.

18. The method of claim 17, wherein digital filtering of the reconstructed power distribution comprises digitally filtering the reconstructed power distribution using a thermal model of the MEMS device.

19. The method of claim 17, wherein digital filtering of the reconstructed power distribution comprises digitally filtering the reconstructed power distribution using an acoustic model of the MEMS device.

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