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How to use the ADAU1772 PGA?

Question asked by ccyao on May 22, 2013
Latest reply on May 24, 2013 by ccyao

We tried to input a 1KHz sine wave to an ADAU1772's analog input pin, and then route the analog input to its serial output.

The voltage level of the ADAU1772 AVDD is 3.3v.

 

The sine wave was played on a computer, and we turned the volume up to 100% in the beginning.

If we disable the PGA (PGA_EN0=0), the external DSP (TI C6713) can receive a full scale sine wave from the ADAU1772,

as shown in the figure below.

line.PNG

 

 

As shown in the figure below, the TI C6713 will receive a distorted sine wave when we enalbe the PGA (PGA_EN0=1, PGA_GAIN0=0)

pga-1.PNG

 

 

If we turn the volume down (decreasing the amplitude of the input sine wave), the sine wave receved by the TI C6713 become a little better,

as shown in the figure below..

pga-2.PNG

 

 

If we keep turning the volume down,  the TI C6713 can receive a similar but downscaled sine wave (0.5 ~ -0.5, peak-to-peak),

We need a correct way to configure the PGA properly. By this way, the TI C6713 can receive a full scale sine wave (1 ~ -1, peak-to-peak),

please help.

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