GENERAL DESCRIPTION
Unlike other ChipCorder series, the ISD3900 provides an I2S digital audio interface, faster digital recording, higher sampling frequency, and a signal path with SNR equivalent to 12bit resolution. The ISD3900 can take digital audio data via I2S or SPI interface. When I2S input is selected, it will replace the analog audio inputs and will support sample rates of 32, 44.1 or 48 kHz depending upon clock configuration. When SPI interface is chosen, the sample rate of the audio data sent must be one of the ISD3900 supported sample rates. The ISD3900 has built-in analog audio inputs, analog audio line driver, and speaker driver output. The two analog audio inputs to the device are: (1) AUXIN has a fixed gain configured by SPI command, and (2) ANAIN/ANAOUT has a fixed gain amplifier with the gain set by two external resistors. ANAIN/ANAOUT can also be used as a microphone differential input (ANAIN/ANAOUT becomes MIC+/MIC-) in conjunction with an automatic gain control (AGC) circuit configured by SPI command.
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