Datasheet

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6.7 Audio Interface Tab
Kit Operation
The IN2L and IN2R inputs are similar to the IN1L and IN1R inputs in that they can be routed to either ADC
input channel. Control of the mic bias is accomplished by using the pull-down menu at the top of these
channel strips. The mic bias can either be powered down or set to 2.0V, 2.5V, or the power supply voltage
of the ADC (AVDD_ADC).
To use the on-board microphone, JMP3 and JMP4 must be installed and nothing should be plugged into
J8. In order for the mic bias settings in the software to take effect, JMP10 should be set to connect
positions 2 and 3, so that mic bias is controlled by the TLV320AIC31.
In the upper right of this tab are controls for Weak Common Mode Bias. Enabling these controls will
result in unselected inputs to the ADC channels to be weakly biased to the ADC common mode voltage.
Below these controls are the controls for the ADC PGA—the master volume controls for the ADC inputs.
Each channel of the ADC can be powered up or down as needed using the Powered Up buttons. PGA
soft-stepping for each channel is selected using the control below this. The large knobs set the actual
ADC PGA Gain; at the extreme counterclockwise rotation, the channel is muted. Rotating the knob
clockwise increases the PGA gain.
The Audio Interface tab sets up the audio data interface to the TLV320AIC31. For use with the PC
software and the USB-MODEVM, the default settings should be used. If using an external I
2
S source, or
other data source, the interface mode may be selected using the Transfer Mode control—selecting either
I
2
S mode, DSP mode, or Right- or Left-Justified modes. Word length can be selected using the Word
Length control, and the bit clock rate can also be selected using the Bit Clock rate control. The Data
Word Offset, used in TDM mode (see the product datasheet ), can also be selected on this tab.
SBAU115 – November 2005 TLV320AIC31EVM and TLV320AIC31EVM-PDK User's Guide 15