Figure 6-19 ADC Signal-Chain Processing Flowchart

The front-end ADC is very low noise, with a 115dB dynamic range performance. This low-noise and low-distortion, multibit, delta-sigma ADC enables the TAC5412-Q1 to record a far-field audio signal with very high fidelity, both in quiet and loud environments. Moreover, the ADC architecture has inherent antialias filtering with a high rejection of out-of-band frequency noise around multiple modulator frequency components. Therefore, the device prevents noise from aliasing into the audio band during ADC sampling. Further on in the signal chain, an integrated, high-performance multistage digital decimation filter sharply cuts off any out-of-band frequency noise with high stop-band attenuation.

The device also has an integrated programmable biquad filter that allows for custom low-pass, high-pass, or any other desired frequency shaping. Thus, the overall signal chain architecture removes the requirement to add external components for antialiasing low-pass filtering and thus saves drastically on the external system component cost and board space. See the TAC5212 Integrated Analog Antialiasing Filter and Flexible Digital Filter application report for further details.

The signal chain also consists of various highly programmable digital processing blocks such as phase calibration, gain calibration, high-pass filter, digital summer or mixer, biquad filters, synchronous sample rate converter, and volume control. The details of these processing blocks are discussed further in this section. The device also supports up to four digital PDM microphone recording channels when the analog recording channels are not used.

The desired input channels for recording can be enabled or disabled by using the CH_EN (P0_R118) register, and the output channels for the audio serial interface can be enabled or disabled by using the ASI_TX_CHx_CFG register. In general, the device supports simultaneous power-up and power-down of all active channels for simultaneous recording. However, based on the application's needs, if some channels must be powered up or powered down dynamically when the other channel recording is on, then that use case is supported by setting the DYN_PUPD_CFG register.

The device supports an input signal bandwidth up to 100kHz, which allows the high-frequency non-audio signal to be recorded by using a 216kHz (or higher) sample rate. Wide bandwidth mode can be enabled or disabled by setting ADC_CHx_BW_MODE bit.

For sample rates of 48kHz or lower, the device supports all features and various programmable processing blocks. However, for sample rates higher than 48kHz, there are limitations in the number of simultaneous channel recordings and playback supported and the number of biquad filters and such. See the TAC5212 Sampling Rates and Programmable Processing Blocks Supported application report for further details.