Texas Instruments TLV320DAC26EVM, Руководство пользователя

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Program Description
3-12
3.5.2.2 Interface Section
By checking Power Up Codec in the Interface section, the audio interface is
powered up.
In this EVM, the audio codec samples at 44.1 kHz in 16-bit I
2
S mode. Also, the
DAC26 codec functions as a slave in the interface. Although the DAC26 device
has much more flexibility, this EVM has these values fixed.
Also, the VBias pin output is selectable by checking the corresponding options:
either at 2.5 VDC or 2.0 VDC, which provides a bias voltage for using an
electret microphone.
3.5.2.3 DAC Section
The DAC26 audio DAC can be powered on by clicking on the power−up DAC
box. By default, the DAC is powered off.
Before a DAC power on, make sure to check the DAC output mode on the EVM
board. If the audio output is connected to J6 or J13, the virtual GND should be
powered up before the DAC powers up. Otherwise, if the audio output is
connected to J7 ( AC coupled plug), the virtual GND should be powered down
before power up.
The stereo audio volumes can be controlled by the left (L) and right (R) volume
control slides in three different ways, selectable through setting the master
volume controller: 1) independent, 2) right channel controlled, or 3) left
channel controlled.
The DAC’s PGA gain can be changed in soft stepping either 0.5-dB per one
sample, or 0.5-dB per 2 samples.
The audio DAC’s output swing range can be set from the list in the Output
Peak-to-Peak Range pulldown menu. See the DAC26 data sheet to find out
the range. Note that the output peak-to-peak range is related to the analog
driver power supply voltage.
By checking the Headphone Amp Enable box, the amplifier 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
capacitor-decoupling mode, the virtual group can be powered down;
otherwise, the DAC output is in capacitor-less mode, and the virtual ground
should be powered up.
3.5.2.4 Sidetone Section
The DAC26 has an analog sidetone and a digital sidetone circuit. The audio
output of the DAC26 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