Texas Instruments TLV320AIC26EVM, Руководство пользователя

Страница: 35 / 46

Program Description
3-19 Operation
By checking the Headphone Amp Enable box, the amp is enabled, which can
directly be connected to a 16-
Ω
load. Otherwise, the headphone driver is
bypassed and the device can have a load of 10 k
Ω
.
By checking the Power Up Virtual GND box, the virtual ground for the
headphone output is powered up. The virtual ground should be powered
up/down according to the DAC output mode. If the DAC output is in
cap-decoupling mode, the virtual group can be powered down, otherwise the
DAC output is in cap-less mode and the virtual ground should be powered up.
3.5.3.4 Sidetone Section
The AIC26 has an analog sidetone and a digital sidetone circuit. The audio
output of the AIC26 includes a mix of the DAC and the sidetone channels, in
proportion to their respective volume settings.
The analog sidetone is enabled when the PowerUp AnaSideTone box is
checked, and available only if the single-ended MICIN or AUX Input Select is
selected as input to the ADC. Its volume can be adjusted by the analog volume
control slider, ranging from 12 dB to −34.5 dB in 0.5-dB steps. The analog
sidetone is muted when the Mute box under the slider is checked. Additionally,
similar to the audio ADC and DAC, the analog sidetone volume change can
be in soft stepping mode if the corresponding box is checked.
The AIC26’s digital sidetone has three settings. The volume is controlled by
the digital slider, which changes from 0 dB to −48 dB in steps of 1.5 dB. The
digital sidetone can be muted by checking the mute box under the volume
control slider. The gain change is implemented with zero crossover, when
enabled by checking the box below the sliders, and a possible pop sound may
be avoided or reduced.
3.5.3.5 Keyclick Section
When the Enable Key Click box is checked, a clicking sound is heard
whenever an audio related setting is selected or checked in the audio screen
or in the PLL section of the configuration screen, or the settings on the Audio
Effects Filters screen (see Figure 3−8).
The volume, frequency, and duration (length) of this keyclick can be adjusted
using the corresponding slider and selectors shown in Figure 3−7.
3.5.4 Audio Effects Filters Screen
The Audio Effects Filters screen displays all of the coefficients for the audio
effects filters of the AIC26, including the bass-boost and other filters, the
de-emphasis filters and the power-up pop noise reduction functions. This
screen is shown in Figure 3−8.