STW5095 datasheet(17/69 Pages) STMICROELECTRONICS

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STw5095

3 Functional Description

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loudspeaker to -6 dB when VCCLS is above 4.2 V, and it removes the limit for VCCLS below

4.0 V. The loudspeaker gain is left unchanged if it is set below -6 dB with bits LSG. This event

(VCCLS > 4.2 V) can generate, if enabled (bit VLSMSK in CR31), an IRQ signal.

3.10

Analog mixer

STw5095 can send to the output drivers the sum of stereo audio signals from 3 different

sources, DA path (bit MIXDAC in CR17), Microphone Preamplifiers (bit MIXMIC in CR17) and

Line In Amplifiers (bit MIXLIN in CR17). The mixer does not have a gain control on the inputs,

therefore the user should reduce the levels of the input signals within the analog signal range.

The stereo Analog Mixer is powered up with bits ENMIXL and ENMIXR in CR2.

3.11

AD path

The AD path converts audio signals from Microphone Preamplifiers (selected with bit ADMIC in

CR17) and Line In Amplifiers (bit ADLIN in CR17) inputs to digital domain. If both inputs are

selected then the sum of the two is converted. After AD conversion the audio data is resampled

with a sample rate converter and then processed with the internal DSP. Two different filters are

selectable in the DSP (bit ADVOICE in CR29): stereo Audio Filter, with DC offset removal and

FIR image filtering; and a standard mono Voice-channel filter (uses left channel input and feeds

both channel output). The AD path includes a digital gain control (ADCLG, ADCRG in CR12

and CR13 respectively) in the range -57 to +8 dB. The maximum gain from Mic Preamplifier to

AD interface is then 47 dB. When Audio filter is selected in both AD and DA paths then DA

audio data can be summed to AD data and sent to the AD Audio Interface (see DA2ADG in

CR15). Left and Right channels can be independently switched on and off to save power, if

needed (bits ENADCL and ENADCR in CR1)

3.12

DA path

The DA path converts digital data from the digital audio interface to analog domain and feeds it

to the analog mixer. Incoming audio data is processed with a DSP where different filters are

selectable (bit DAVOICE in CR29): Audio Filter, stereo, with FIR image filtering, bass and treble

controls (bits BASS and TREBLE in CR14), de-emphasis filter; and a standard Voice-channel

filter, mono (uses left channel input and feeds both channel output). A dynamic compression

function is available for both audio and voice filters (bit DYNC in CR14). The DA path includes a

digital gain control (DACLG, DACRG in CR10 and CR11 respectively) in the range -65 to 0 dB.

AD to DA mixing (sidetone) can be enabled: see CR16 for details. Left and Right channel can

be independently switched on and off to save power, if needed (bits ENDACL and ENDACR in

CR1)

3.13

Analog-only operation

STw5095 can operate without AMCK master clock if analog-only functions are used. It is

possible to mix Microphone and Line In preamplifiers signals and listen through headphones,

loudspeaker or send them to line-out. The analog-only operation is enabled with bit ENOSC in

CR0. When ENOSC=1 the AD and DA paths cannot be used.

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