The CS53L21 is a highly integrated, 24-bit, 96kHz, low power stereo audio A/D converter (ADC). Based on multibit, delta sigma modulation, it allows infinite sample rate adjustment between 4kHz and 96kHz and offers many features suitable for low power, portable-system applications. The ADC input path allows independent channel control of a number of features. An input multiplexer selects between line-level or microphone-level inputs for each channel. The microphone input path includes a selectable programmable-gain pre-amplifier stage and a low noise MIC bias voltage supply. A PGA is available for line or microphone inputs and provides analog gain with soft ramp and zero cross transitions. The ADC also features a digital volume attenuator with soft ramp transitions. A programmable ALC and Noise Gate monitor the input signals and adjust the volume levels appropriately. The signal processing engine (SPE) controls left/right channel volume mixing, channel swap and channel mute functions. All volume-level changes may be configured to occur on soft ramp and zero cross transitions. In addition to its many features, the CS53L21 operates from a single, low-voltage analog and digital core power supply, making this ADC ideal for applications such as portable audio players, digital microphones, digital voice recorders, voice recognition systems and audio/video capture cards.