The device supports up to 12 programmable digital biquad filters available for ADC signal chain limited to 3/channel. These highly efficient filters achieve the desired frequency response. The TAC5111 also supports on-the-fly programmable Biquad filters for two-channel record use cases. In digital signal processing, a digital biquad filter is a second-order, recursive linear filter with two poles and two zeros. Equation 4 gives the transfer function of each biquad filter:

Equation 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 low-pass, high-pass, or any other desired frequency shaping. The programmable coefficients for the mixer operation are located in the and sections. If biquad filtering is required, then the host device must write these coefficient values before powering up any ADC channels for recording. In two-channel use case, the TAC5111 also supports on-the-fly programmable filters. In this case, the Device uses two banks of filters for one channel with a switch bit to perform the switch from one filter bank to the other. As described in Table 7-31, these biquad filters can be allocated for each output channel based on the ADC_DSP_BQ_CFG[1:0] register setting of P0_R114. 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 TAC5212 Programmable Biquad Filter Configuration and Applications application report for further details.

Table 7-32 shows the biquad filter coefficients mapping to the register space.