ZHCSGM5A August 2017 – November 2017 TLV320AIC3109-Q1
PRODUCTION DATA.
The audio DAC includes a digital volume control block that implements a programmable digital gain. The volume level can be varied from 0 dB to –63.5 dB in 0.5-dB steps, or set to mute, independently for each channel. The volume level can also be changed by the master volume control. Gain changes are implemented with a soft-stepping algorithm that only changes the actual volume by one step per input sample, either up or down, until the desired volume is reached. The rate of soft-stepping can be slowed to one step per two input samples through a register bit.
The host does not know when the DAC is muted because of the soft-stepping, which may be important if the host wishes to mute the DAC before making a significant change, such as changing sample rates. In order to help with this situation, the device provides a flag back to the host via a read-only register bit that alerts the host when the device completes the soft-stepping and the actual volume reaches the desired volume level. The soft-stepping feature can be disabled through register programming. If soft-stepping is enabled, keep the MCLK signal applied to the device until the DAC power-down flag is set. When this flag is set, the internal soft-stepping process and power-down sequence is complete, and the MCLK can then be stopped if desired.
The TLV320AIC3109-Q1 also includes functionality to detect when the selection of de-emphasis or digital audio processing functionality is changed. When the new selection is detected, the TLV320AIC3109-Q1 (1) soft-mutes the DAC volume control, (2) changes the operation of the digital effects processing to match the new selection, and (3) soft-unmutes the device. These steps avoid any possible pops or clicks in the audio output resulting from instantaneous changes in the filtering. A similar algorithm is used when first powering up or powering down the DAC. The circuit begins operation at power-up with the volume control muted, then soft-steps the volume up to the desired level. At power-down, the logic first soft-steps the volume down to a mute level, then powers down the circuitry.