User's Manual

FLC-BTM501 Datasheet
Flaircomm Microelectronics Confidential
-14-
4.3 Audio Interfaces
Audio interface provides following features:
 Mono analogue input for voice band and audio band
 Stereo and mono analogue output for voice band and audio band
Digital
Circuitry
∑△-ADC
Input
Amplifier
DAC
DAC
LP Filter
LP Filter
Output
Amplifier
Output
Amplifier
MIC_LP
MIC_LN
SPK_LP
SPK_LN
SPK_RP
SPK_RN
Figure 3: Audio Input and Output
The stereo audio CODEC uses a fully differential architecture in the analogue signal path, which
results in low noise sensitivity and good power supply rejection while effectively doubling the signal
amplitude. It operates from a single power-supply of 1.5V and uses a minimum of external
components. The module features a differential stereo audio output interfaces.
4.3.1 ADC
The ADC consists of a second order Digma Delta converter as show in Figure 3.
4.3.2 ADC Sample Rate Selection and Warping
ADC supports the following sample rates: 8kHz, 11.025kHz, 16kHz, 22.05kHz, 24kHz, 32kHz,
44.1kHz.
One of the main concerns for stereo wireless music applications is the ability to keep sampl rates for
the CODECs at both ends of the wireless link in synchronization. A VM function adjusts the sample
rate using a ‘warping’ function to tune the sample rate to the required value. The ADC warp function
allows the sample rate to be changed by +/-3%, in steps of 1/2
17
, or 7.6ppm. The warp function
preserves the signal quality – the distortion introduced when warping the sample rate is negligible.
4.3.3 ADC Gain
The ADC contains two gain stages for each channel, an analogue and a digital gain stage.