Filtering architecture with transients minimization due to temporary scaling
A digital filter includes a delay line; coefficients coupled to the delay line; and a summer coupled to at least one of the of coefficients, wherein the coefficients each include a first value during a normal mode of operation, and wherein at least one of the coefficients comprises a second value during a transient mode of operation.
1 . A digital microphone comprising:
a programmable gain amplifier (PGA);
an analog-to-digital converter (ADC) coupled to the PGA;
a digital filter coupled to the ADC, wherein the digital filter comprises a plurality of coefficients; and
a digital gain compensation component coupled to the digital filter,
wherein the plurality of coefficients each comprise a first value during a normal mode of operation of the digital microphone, wherein at least one of the plurality of coefficients comprises a second value during a first cycle of a transient mode of operation of the digital microphone, and wherein at least two of the plurality of coefficients comprise the second value during a second cycle of the transient mode of operation.
2 . The digital microphone of claim 1 , wherein the digital filter comprises:
a delay line including a plurality of serially coupled delay components;
a plurality of coefficients coupled to corresponding delay components of the delay line, wherein the plurality of coefficients comprise a volatile memory component, a non-volatile memory component, or a lookup table (LUT); and
a summer coupled to at least one of the plurality of coefficients.
3 . The digital microphone of claim 2 , wherein a length of the transient mode of operation corresponds to an order of the digital filter.
4 . The digital microphone of claim 2 , wherein the digital filter comprises a digital finite impulse response (FIR) filter.
5 . The digital microphone of claim 2 , wherein the digital filter comprises a digital infinite impulse response (IIR) filter.
6 . The digital microphone of claim 5 , wherein the digital IIR filter comprises a second order direct form digital IIR filter.
7 . The digital microphone of claim 5 , wherein the digital IIR filter comprises a second order canonical form digital IIR filter.
8 . The digital microphone of claim 1 , wherein at least another of the plurality of coefficients comprises both the first value and the second value during the transient mode of operation.
9 . The digital microphone of claim 1 , wherein at least another of the plurality of coefficients comprises only the first value during the transient mode of operation.
10 . The digital microphone of claim 1 , wherein the normal mode of operation comprises a first portion corresponding to a first gain value of the digital microphone, and wherein the normal mode of operation comprises a second portion corresponding to a second gain value of the digital microphone.
11 . The digital microphone of claim 10 , wherein the transient mode of operation is interposed between the first portion of the normal mode of operation and the second portion of the normal mode of operation.
12 . A method of operating a digital microphone, the method comprising:
adjusting a gain of a signal path of the digital microphone, wherein the signal path comprises a programmable gain amplifier (PGA), an analog-to-digital converter (ADC) coupled to the PGA, a filter coupled to the ADC, wherein the filter comprises a plurality of coefficients, and a digital gain compensation component coupled to the filter, wherein adjusting the gain of the signal path of the digital microphone further comprises:
setting a coefficient of the filter of the digital microphone to a first value during a normal mode of operation of the digital microphone;
setting the coefficient of the filter of the digital microphone to a second value during a first cycle of a transient mode of operation of the digital microphone; and
setting at least two coefficients of the filter of the digital microphone to the second value during a second cycle of the transient mode of operation of the digital microphone.
13 . The method of claim 12 , further comprising setting at least another coefficient of the filter to both the first value and to the second value during the transient mode of operation.
14 . The method of claim 12 , further comprising setting at least another coefficient of the filter to only the first value during the transient mode of operation.
15 . The method of claim 12 , wherein the normal mode of operation comprises a first portion corresponding to a first gain value of the digital microphone, and wherein the normal mode of operation comprises a second portion corresponding to a second gain value of the digital microphone.
16 . The method of claim 15 , wherein the transient mode of operation is interposed between the first portion of the normal mode of operation and the second portion of the normal mode of operation.
17 . A digital microphone comprising:
a programmable gain amplifier (PGA);
an analog-to-digital converter (ADC) coupled to the PGA;
a digital filter coupled to the ADC, wherein the digital filter comprises a plurality of coefficients; and
a digital modulator coupled to the digital filter,
wherein the plurality of coefficients each comprise a first value during a normal mode of operation of the digital microphone, wherein at least one of the plurality of coefficients comprises a second value during a first cycle of a transient mode of operation of the digital microphone, and wherein at least two of the plurality of coefficients comprise the second value during a second cycle of the transient mode of operation.
18 . The digital microphone of claim 17 , wherein at least another of the plurality of coefficients comprises both the first value and the second value during the transient mode of operation.
19 . The digital microphone of claim 17 , wherein at least another of the plurality of coefficients comprises only the first value during the transient mode of operation.
20 . The digital microphone of claim 17 , wherein the normal mode of operation comprises a first portion corresponding to a first gain value of the digital microphone, and wherein the normal mode of operation comprises a second portion corresponding to a second gain value of the digital microphone.
21 . The digital microphone of claim 20 , wherein the transient mode of operation is interposed between the first portion of the normal mode of operation and the second portion of the normal mode of operation.