SBAS906 March 2018 TLV320ADC3100
PRODUCTION DATA.
The TLV320ADC3100 includes a stereo audio ADC that uses a delta-sigma modulator with 128-times oversampling in single-rate mode, followed by a digital decimation filter. The ADC supports sampling rates from 8 kHz to 48 kHz in single-rate mode, and up to 96 kHz in dual-rate mode. Whenever the ADC is in operation, the device requires that an audio master clock be provided and appropriate audio clock generation be set up within the device.
In order to provide optimal system power dissipation, the stereo ADC can be powered one channel at a time, to support when only mono record capability is required. In addition, both channels can be fully or partially powered down.
The integrated digital decimation filter removes high-frequency content and down-samples the audio data from an initial sampling rate of 128 fS to the final output sampling rate of fS. The decimation filter provides a linear phase output response with a group delay of 17 / fS. The –3-dB bandwidth of the decimation filter extends to 0.45 fS and scales with the sample rate (fS). The filter has a minimum 73-dB attenuation over the stop band from 0.55 fS to 64 fS. Independent digital high-pass filters are also included with each ADC channel, with a corner frequency that can be set independently by programmable coefficients or can be disabled entirely.
Because of the oversampling nature of the audio ADC and the integrated digital decimation filtering, requirements for analog antialiasing filtering are relaxed. The TLV320ADC3100 integrates a second-order analog antialiasing filter with 20-dB attenuation at 1 MHz. This filter, combined with the digital decimation filter, provides sufficient antialiasing filtering without requiring additional external components.
The ADC is preceded by a programmable gain amplifier (PGA) that allows analog gain control from 0 dB to 40 dB in steps of 0.5 dB. The PGA gain changes are implemented with an internal soft-stepping algorithm that only changes the actual volume level by one 0.5-dB step every one or two ADC output samples, depending on the register programming (see register page 0, register 81). This soft-stepping specifies that volume control changes occur smoothly with no audible artifacts. On reset, the PGA gain defaults to a mute condition, and upon power down, the PGA soft-steps the volume to mute before shutting down. A read-only flag is set whenever the gain applied by the PGA equals the desired value set by the register. The soft-stepping control can also be disabled by programming a register bit.