STW5094A Datasheet, PDF (8/51 Pages) STMicroelectronics – 18-bit Low Power Asynchronous Stereo Audio DAC with Integrated Power Amplifiers and Voice Codec

STw5094A
FUNCTIONAL DESCRIPTION
1 DEVICE MODES
STw5094A can work in 4 different modes, selected by bits MD in Control Register 21 (CR21). Depending
on the mode different data interfaces, clock inputs, and internal blocks are selected. A built-in power con-
sumption management function keeps in power down the blocks that are not needed by the selected op-
erating mode. In all the modes the Output Drivers can be activated in different combinations with bits PLS,
PHL, PHR in CR6 (in case of stereo input and LSP ⁄ N driver selected the Left channel is sent to this
driver, while in case of voice input and HPL + HPR drivers selected the same signal is sent to both driv-
ers).
1.1 Audio Mode
In Audio mode the path from the Audio interface (Au I ⁄ F) to the output drivers is active to allow the Stereo
Audio DAC function. The Au I ⁄ F is active while the PCM I ⁄ F is inactive.
The master clock of the device is AMCK. The AMCK frequency is fixed, and independent from the audio
samples data rate (LRCK frequency). AMCK source can be any fixed system clock whose nominal fre-
quency value lies in the range 9.5MHz to 28MHz (the full range is covered in three sub-ranges, selected
by bits AMCK_DIV in CR18). The rate of the audio data (LRCK frequency) can be any value in the range
8kHz to 48kHz (non standard values are allowed) and does not need to be specified.
Since the AMCK clock is used directly in the D to A Converters section, its jitter and spectral properties
must be adequate to the desired Audio quality.
In Audio Mode there are additional functions for audio signal processing:
– A digital volume control with 54 dB range is implemented (bits VOL in CR20). If the digital volume is
used in addition with the analog gain regulation a 94dB range volume is obtained.
– Bass controls can be regulated in the -12.5dB to +12.5dB range in 2.5 dB step (bits BASS in CR19).
– Treble controls can be regulated in the -6dB to +6dB range in 2 dB step (bits TREBLE in CR19).
– The 50µs ⁄ 15µs de-emphasis filter is activated instead of treble controls (bits TREBLE in CR19).
Note: the time constants are referred to the 44.1kHz FS.
– A dynamic range compressor is implemented (bit CMP in CR20).
Note:The de-emphasis filter and the Bass/Treble controls freq. responses scale with the input sampling rate.
The tone⁄ ring⁄ DTMF generator can be activated if needed. In audio mode the frequency values of the
tones is a function of the AMCK frequency value as explained in Table 1.
1.2 Voice Mode
In Voice mode the TX path from microphone input to DX and the RX path from DR to the output drivers
are active to allow the PCM CODEC function. The PCM I ⁄ F is active while the Au I ⁄ F is inactive.
The master clock of the device is MCLK, the frequency of the clock can be selected with bits F in CR0.
The tone⁄ ring⁄ DTMF generator can be activated if needed.
1.3 Tone Only Mode
In tone only mode the path from the tone generator to the output drivers and to the buzzer is active to allow
tones or ringer listening only. Both Au I⁄ F and PCM I⁄ F are inactive, as all the Audio and Voice converters
functions.
The master clock of the device can be selected to be AUXCLK, MCLK or AMCK (bits CFM in CR21).
1.4 FM Mode
In FM mode the path from FML and FMR analog inputs to the output Drivers is active to allow FM Stereo
Radio listening. Both Au I ⁄ F and PCM I ⁄ F are inactive, as all the Audio and Voice converters functions.
The master clock of the device can be selected to be AUXCLK, MCLK or AMCK (bits CFM in CR21).
The Tone ⁄ Ring ⁄ DTMF generator is in power down.
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