From the microphone Sensitivity of -42dBV and SNR of 60dB, the lowest or smallest input level the microphone can record is -102dBV which is equivalent to 7.94μVrms single-ended. A 1KHz tone with 7.94μVrms is applied to the analog AC-Coupled differential inputs of the device under test (DUT) with 0dB gain setting and the digital output is captured with Audio Precision. In ADC6120, we run with and without Dynamic Range Enhancer (DRE) for comparison. DRE is a feature which basically amplify low level signal with the low noise PGA when the feature is below the DRE threshold. This DRE feature is available only in the ADC with PGA converter and not available in the new architecture ADC.

Figure 3-2 TAA5212 Captured of Minimum Mic Input

Figure 3-3 ADC6120 Captured of Minimum Mic Input With DRE Disable

Figure 3-4 ADC6120 Captured of Minimum Mic Input With DRE Enable

As shown in the previous results, the two devices are capable of capturing the microphone lowest level of -108dBr without any amplification needed. The rms level of the converters shows a 6dB delta due to the differential configuration setting and the dynamic range of the un-weighted test is about 2dB down from the A-weighted setting as expected. Also, the DRE feature in the ADC6120 shows an increase in the dynamic range at this low signal level compare to DRE disable.