We have connected an arbitration generator with the TLV320ADC3101 Evaluation Module (EVM) from TI and transferred the digital output data to the PC via USB. On the PC we recorded the audio stream with different settings for the fine volume control. On the Screenshot below you can see the settings 0, -0.1, -0.2, -0.3db from top to bottom. There's no change in amplitude when changing fine volume control. The amplitude of the sine changes slowly for a fixed setting of fine volume control?!
The next picture shows the same data when zoomed in. We can see the amplitudes of the sine signal.
The setting -0.4dB is not shown in the pictures above. When we use this setting, the amplitude changes to 0.9 (see scale above). Thats the same amplitude jump we can see in the analogue output signal in our devices. All other settings have no effect.
Thanks
Marc