Datasheet

Program Description

3-18

3.5.4.1 Codec Section

By checking Power Up Codec in the codec section, the audio codec is powered

up.

In this EVM, the audio codec samples at 44.1 kHz in 16-bit I

S mode. Also, the

TSC2100 codec functions as a slave in the interface. Although the TSC2100

device has much more flexibility, this EVM has these values fixed.

3.5.4.2 ADC Section

By checking Power Up ADC, audio ADC power is enabled.

The audio ADC also has a high-pass filter which is a submultiple of the sample

rate, to remove dc or low frequency components from the input signal.

The input signal to the audio ADC can come from: 1) the pin MICIN, a

single-ended input; 2) the pin AUX, also a single-ended input; or 3) the pin

MIC2IN and AUX, a differential input, selectable through the Input Select box.

Figure 3−8 shows the single-ended input from MICIN (if selected).

A microphone bias voltage of either 2.5 V or 2.0 V can also be generated by

the TSC2100 (refer to Figure 3−8). Note that to use the microphone bias

voltage, jumper JMP2 should be set to position 2 to 3 (refer to Table 3−1 of this

document for jumper settings).

If the differential microphone inputs to the EVM (through the microphone jack

J5) the JMP1 should be installed, and the input select should be set to DIFF

(MIC/AUX) in this section.

In the ADC input path, there is a programmable EVM amplifier (ADC PGA),

allowing analog input gain control from 0 dB to 59 dB. When not using

automatic gain control (AGC OFF), moving the volume slide adjusts the PGA

and checking the Mute box mutes the ADC signal.

When the gain changes from the current value to the programmed value, it

changes in steps of 0.5 dB. Also, the change rate can be controlled if the PGA

Soft Stepping box is checked, where the PGA changes 0.5 dB at either 1 step

per sample or 1 step per 2 samples.

Automatic gain control (AGC) is another more sophisticated way to control the

ADC gain. When the box by AGC ON is checked, AGC is enabled, as shown

in Figure 3−9. Refer to the TSC 2100 data sheet for setting and using the AGC.