STW5095_07 Datasheet, PDF (16/73 Pages) STMicroelectronics – Low-power asynchronous stereo audio Codec with integrated power amplifiers

STw5095
Functional description
4.5
Note:
Data rates
STw5095 supports any data rate in 2 ranges: 8 kHz to 48 kHz and 88 kHz to 96 kHz. The
range is selected with bits DA96K and AD96K in CR29 for AD and DA paths respectively.
When AD96K=1 it is required to have DA96K=1.
The rates are fully independent in A/D and D/A paths. Moreover the rates do not have to be
specified to the device and they can change on the fly, within one range, while data is
flowing.
The 2 audio data interfaces (for A/D and D/A) can independently operate in master or slave
mode.
4.6
Clock generators and master mode function
STw5095 provides 2 internal clock generators that can drive, if needed, the audio interfaces
(master mode), and/or two independent master clocks.
The AMCK clock input frequency is internally raised via a PLL to obtain a clock (MCK) in the
range 32 MHz to 48 MHz. The ratio MCK/AMCK is defined in CR30 (see MCKCOEFF in
Section 5.6 on page 34).
MCK is used to obtain, by fractional division, the oversampled clock (OCK), word clock
(SYNC) and bit clock (CK), that will therefore have edges aligned with MCK (the OCK period
can have jitter of 1 MCK period).
The frequency of OCK, SYNC and CK is set with DAOCKF in CR21/20 for DA interface, and
ADOCKF in CR24/23 for AD interface.
The ratio between OCK and SYNC clocks is selected with bit DAOCK512 in CR22 for DA
interface and bit ADOCK512 in CR25 for AD interface. The ratio between CK and SYNC
clocks depends on the selected interface format (see Audio digital interfaces paragraph
below). Note that SPI format can only be slave.
The ADOCK and DAOCK output clocks are activated by bits ENADOCK and ENDAOCK
respectively, while master mode generation is activated with two bits: first ADMAST
(DAMAST) sets ADSYNC and ADCK (DASYNC and DACK) pins as outputs, then
ADMASTGEN (DAMASTGEN) generates the SYNC and CK clocks. The logical value at
SYNC and CK pins before data generation depends on the interface selected format.
See description of CR20 to CR25 for further details.
4.7
Audio digital interfaces
Two separate audio data interfaces are provided for AD and DA paths to have maximum
flexibility in communicating with other devices. The 2 interfaces can have different rates and
can work in different formats and modes (i.e AD interface can be 8 kHz PCM slave while DA
is 44.1 kHz I²S master).
The pins used by the interfaces are:
AD_SYNC, AD_CK and AD_DATA for AD path word clock, bit clock and data, respectively,
and
DA_SYNC, DA_CK and DA_DATA for DA path word clock, bit clock and data, respectively.
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