In this test case, we add gain from the audio device to -1dBr of the device input full-scale. In the TAX5XXX device, the gain is set through Digital Volume (DVOL) and for ADC6120 device, the gain is set through the PGA register.

From the maximum input level of the microphone measured previously, we apply +19dB gain to bring the record audio path level to -1dBr of full-scale.

Figure 3-18 TAA5212 Captured of Maximum Mic Input With +19dB Gain

Figure 3-19 ADC6120 Captured of Maximum Mic Input With +19dB Gain

Figure 3-20 ADC6120 Captured of Maximum Mic Input With +19dB Gain and DRE Enable

In TAX5XXX, adding the DVOL gain to the input level does not change the THDN level, but in the ADC6120 device with PGA gain it improves THDN. This increase is due to ADC noise is less dominant than the PGA thus THDN is better.