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8.3.6.5 Programmable Digital Biquad Filters

The device supports up to 12 programmable digital biquad filters. These highly efficient filters achieve the

desired frequency response. In digital signal processing, a digital biquad filter is a second-order, recursive linear

filter with two poles and two zeros. Equation 2 gives the transfer function of each biquad filter:

*:V; =

00 + 201VF

1 + 02VF2

231 F 2&1VF

1 F &2VF2

(2)

The frequency response for the biquad filter section with default coefficients is flat at a gain of 0 dB (all-pass

filter). The host device can override the frequency response by programming the biquad coefficients to achieve

the desired frequency response for a low-pass, high-pass, or any other desired frequency shaping. The

programmable coefficients for the mixer operation are located in the Programmable Coefficient Registers: Page

2 and Programmable Coefficient Registers: Page 3 sections. If biquad filtering is required, then the host device

must write these coefficients values before powering up any ADC channels for recording. As described in Table

8-19, these biquad filters can be allocated for each output channel based on the BIQUAD_CFG[1:0] register

setting of P0_R108. By setting BIQUAD_CFG[1:0] to 2'b00, the biquad filtering for all record channels is disabled

and the host device can choose this setting if no additional filtering is required for the system application. See

the TLV320ADCx140 Programmable Biquad Filter Configuration and Applications application report for further

details.

Table 8-19. Biquad Filter Allocation to the Record Output Channel

PROGRAMMABLE

BIQUAD FILTER

RECORD OUTPUT CHANNEL ALLOCATION USING P0_R108_D[6:5] REGISTER SETTING

BIQUAD_CFG[1:0] = 2'b01

(1 Biquad per Channel)

BIQUAD_CFG[1:0] = 2'b10 (Default)

(2 Biquads per Channel)

BIQUAD_CFG[1:0] = 2'b11

(3 Biquads per Channel)

Biquad filter 1

Allocated to output channel 1

Biquad filter 2

Allocated to output channel 2

Biquad filter 3

Allocated to output channel 3

Biquad filter 4

Allocated to output channel 4

Biquad filter 5

Not used

Allocated to output channel 1

Biquad filter 6

Not used

Allocated to output channel 2

Biquad filter 7

Not used

Allocated to output channel 3

Biquad filter 8

Not used

Allocated to output channel 4

Biquad filter 9

Not used

Allocated to output channel 1

Biquad filter 10

Not used

Allocated to output channel 2

Biquad filter 11

Not used

Allocated to output channel 3

Biquad filter 12

Not used

Allocated to output channel 4

Table 8-20 shows the biquad filter coefficients mapping to the register space.

Table 8-20. Biquad Filter Coefficients Register Mapping

PROGRAMMABLE BIQUAD

FILTER

BIQUAD FILTER COEFFICIENTS

PROGRAMMABLE BIQUAD

FILTER

BIQUAD FILTER COEFFICIENTS

Biquad filter 1

P2_R8-R27

Biquad filter 7

P3_R8-R27

Biquad filter 2

P2_R28-R47

Biquad filter 8

P3_R28-R47

Biquad filter 3

P2_R48-R67

Biquad filter 9

P3_R48-R67

Biquad filter 4

P2_R68-R87

Biquad filter 10

P3_R68-R87

Biquad filter 5

P2_R88-R107

Biquad filter 11

P3_R88-R107

Biquad filter 6

P2_R108-R127

Biquad filter 12

P3_R108-R127

TLV320ADC3120

SBASA91A – DECEMBER 2020 – REVISED JUNE 2021

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