SBAA378B November   2019  – December 2023 PCM3140-Q1 , PCM5140-Q1 , PCM6140-Q1 , TLV320ADC3140 , TLV320ADC5140 , TLV320ADC6140

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Infinite Impulse Response Filters
    1. 2.1 Digital Biquad Filter
  6. 3  TLV320ADCx140/PCMx140-Q1 Digital Biquad Filters
    1. 3.1 Filter Design Using PurePath™ Console
      1. 3.1.1 Example Generating Programmable Biquad Coefficients Using PurePath Console
    2. 3.2 How to Generate N0, N1, N2, D1, and D2 Coefficients with a Digital Filter Design Package
    3. 3.3 Avoid Overflow Conditions
    4. 3.4 Digital Biquad FiIter Allocation to Output Channel
    5. 3.5 Programmable Coefficient Registers for Digital Biquad Filters 1–6
    6. 3.6 Programmable Coefficient Registers for Digital Biquad Filters 7–12
  7. 4 How to Program the Digital Biquad Filters on TLV320ADCx140/PCMx140-Q1
  8. 5 Typical Audio Applications for Biquad Filtering
    1. 5.1 Parametric Equalizers
  9. 6 Crossover Networks
  10. 7 Voice Boost
  11. 8 Bass Boost
  12. 9 Removing 50 Hz–60 Hz Hum With Notch Filters
  13. 10Revision History
  14. 11Digital Filter Design Techniques
    1. 11.1 Analog Filters

3.1 Filter Design Using PurePath™ Console

To facilitate the use of the Digital Biquad Filters, the PurePath™ Console includes a graphical filter design section that plots the magnitude, phase, and group delay versus frequency. This filter design also generates the coefficients through several different filter design techniques filters. Equation 3 shows the available filter design options with a short description of the filter type. In Table 3-1, the cutoff frequency refers to the frequency when the response changes by 3 dB from the passband.

Table 3-1 PurePath™ Console Digital Biquad Filter Options
FILTER TYPE DESCRIPTION
Band Pass Band-Pass filter at the specified center frequency and passband width (filter bandwidth)
Bass Shelf Specified gain applied at the low frequency up to the specified cutoff frequency
Equalizer (Bandwidth) Band-pass filters at the specified center frequency and passband width, with the specified gain
Equalizer (Q Factor) Band-pass filter at the specified center frequency and quality factor, with the specified gain. The quality factor is the center frequency divided by the passband width.
Gain All pass filter at the specified gain
High-Pass Butterworth 1 First-order high-pass filter with specified gain, specified cutoff frequency, maximally flat passband and stopband response. Stopband frequency response has a –10 dB / decade slope.
High-Pass Butterworth 2 Second-order high-pass filter with specified gain, specified cutoff frequency, maximally flat passband and stopband response. Stopband frequency response has a –20 dB / decade.
High-Pass Bessel 2 Second-order high-pass filter with specified gain, specified cutoff frequency, maximally flat phase and constant group delay across passband.
High-Pass Linkwitz Riley 2 Second-order high-pass filter composed of a Butterworth filter with –3 dB at the cutoff frequency. When cascading a low-pass and high-pass Linkwitz Riley filters, the overall gain at the crossover frequency is 0 dB.
High-Pass Variable Q 2 Second-order high-pass filter at the specified center frequency, gain, and quality factor. The quality factor is the center frequency divided by the passband width.
High-Pass Chebyshev High-pass filter with equiripple in the passband with maximally flat response in stopband
Low-Pass Butterworth 1 First-order low-pass filter with specified gain, specified cutoff frequency, maximally flat passband and stopband response. Stopband frequency response has a –10 dB / decade slope.
Low-Pass Butterworth 2 Second-order low-pass filter with specified gain, specified cutoff frequency, maximally flat passband and stopband response. Stopband frequency response has a –20 dB / decade.
Low-Pass Bessel 2 Second-order low-pass filter with specified gain, specified cutoff frequency, maximally flat group delay across passband
Low-Pass Linkwitz Riley 2 Second-order low-pass filter composed of a Butterworth filter with –3 dB at the cutoff frequency. When cascading a low-pass and high-pass Linkwitz Riley filters, the overall gain at the crossover frequency is 0 dB.
Low-Pass Variable Q 2 Second-order low-pass filter at the specified center frequency, gain and quality factor. The quality factor is the center frequency divided by the passband width.
Low-Pass Chebyshev Low-pass filter with equiripple in the passband with maximally flat response in stopband
Notch Band stop filter at the specified center frequency and stopband width (filter bandwidth)
Phase Shift All pass filter with 180 degree phase shift at the specified center frequency through the width given by the bandwidth
Treble Shelf Specified gain applied at the high frequencies past the specified cutoff frequency