STW5095T datasheet(20/73 Pages) STMICROELECTRONICS

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STw5095

Functional description

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with bits LSG. This event (VCCLS > 4.2 V) can generate, if enabled (bit VLSMSK in CR31),

an IRQ signal.

4.10

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.

4.11

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)

4.12

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)

4.13

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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