An analog microphone with an ADC system based on Texas Instruments’ TLV320ADC51x0/PCM51x0-Q1 uses multi-bit modulation ADC to project audio data with a range higher than 24-bit, along with I2S (or PCM, TDM, DSP) interface, as shown in Figure 3-2. This is unlike the PDM microphone, which uses the 1-bit modulation with PDM interface. For the analog microphone with ADC to project as shown in Figure 3-2, the I2S audio signal of ADC output requires one or two more interface lines than the two of the PDM signals. The analog microphone has advantages in in-band (20 Hz to 20 KHz) and out-of-band (above 20 KHz) for quantization noise characteristics (further explained in Section 4). This is because while the digital PDM microphone uses a 1-bit ADC modulator with a 3.072 MHz clock, an analog microphone with ADC (Texas Instruments’ TLV320ADC51x0/PCM51x0-Q1) uses multi-bit architecture with a modulator clock of 6.144 MHz, which allows it to have superior qualities in quantization noise density.

Figure 3-2 Analog Microphone with ADC for Multi-bit Output