PCMD3140IRTER datasheet(33/106 Pages) TI

33 / 106 page

7.3.6.7 Configurable Digital Decimation Filters

The device record channel includes a high dynamic range, built-in digital decimation filter to process the

oversampled PDM data stream from the digital microphone to generate digital data at the same Nyquist

sampling rate as the FSYNC rate. The decimation filter can be chosen from three different types, depending

on the required frequency response, group delay, and phase linearity requirements for the target application. The

selection of the decimation filter option can be done by configuring the DECI_FILT (P0_R107_D[5:4]) register

bits. Table 7-18 shows the configuration register setting for the decimation filter mode selection for the record

channel.

Table 7-18. Decimation Filter Mode Selection for the Record Channel

P0_R107_D[5:4] : DECI_FILT[1:0]

DECIMATION FILTER MODE SELECTION

00 (default)

Linear phase filters are used for the decimation

Low latency filters are used for the decimation

Ultra-low latency filters are used for the decimation

Reserved (do not use this setting)

7.3.6.7.1 Linear Phase Filters

The linear phase decimation filters are the default filters set by the device and can be used for all applications

that require a perfect linear phase with zero-phase deviation within the pass-band specification of the filter.

The filter performance specifications and various plots for all supported output sampling rates are listed in this

section.

7.3.6.7.1.1 Sampling Rate: 7.35 kHz to 8 kHz

Figure 7-19 and Figure 7-20 respectively show the magnitude response and the pass-band ripple for a

decimation filter with a sampling rate of 7.35 kHz to 8 kHz. Table 7-19 lists the specifications for a decimation

filter with a 7.35-kHz to 8-kHz sampling rate.

Normalized Frequency (1/fS)

0.4

0.8

1.2

1.6

2.4

2.8

3.2

3.6

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

D001

Figure 7-19. Linear Phase Decimation Filter

Magnitude Response

Normalized Frequency (1/fS)

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

-0.5

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

D001

Figure 7-20. Linear Phase Decimation Filter Pass-

Band Ripple

Table 7-19. Linear Phase Decimation Filter Specifications

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Pass-band ripple

Frequency range is 0 to 0.454 × fS

–0.05

0.05

Stop-band attenuation

Frequency range is 0.58 × fS to 4 × fS

72.7

Frequency range is 4 × fS onwards

81.2

Group delay or latency

Frequency range is 0 to 0.454 × fS

17.1

1/fS

www.ti.com

PCMD3140

SBASA64A – DECEMBER 2020 – REVISED JUNE 2021

Submit Document Feedback

Product Folder Links: PCMD3140

PCMD3140IRTER Datasheet(PDF) 33 Page - Texas Instruments

PCMD3140IRTER Datasheet(HTML) 33 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL