STV8216 datasheet(22/97 Pages) STMICROELECTRONICS

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Audio Processor Block

STV82x6

22/97

3.7

Automatic Loudness Control

As the human ear does not hear the audio frequency range the same way depending on the power

of the audio source, the Loudness Control corrects this effect by sensing the volume level and then

boosting bass and treble frequencies proportionally to middle frequencies at lower volume.

While maintaining the amplitude of the 1 kHz components at an approximately constant value, the

gain values of lower and higher frequencies are automatically progressively amplified up to +18 dB

when the audio volume level decreases.The maximum treble amplification can be adjusted from

0 dB (first order loudness) to +18 dB (second order loudness). As the volume is proportional to the

external audio amplification power, the loudness amplification threshold is programmable in order to

tune the absolute level. The Loudspeaker Loudness function is enabled by setting the LOUD_ON bit

in register LS_LOUD. The Loudness Threshold and Maximum Treble Gain values are also

programmed in this register.

Two bass cut-off frequencies are available:

● 40 Hz for Normal mode

● 120 Hz for Bass Amplified mode

The mode is selected by the LOUD_FREQ bit in register LS_LOUD (66h).

3.8

Subwoofer Control

The subwoofer signal is created by adding the bass frequency of the Left/Right Loudspeaker

channels. The Subwoofer output is enabled by setting the SW_ON bit in register ANA_LS_HP. This

will also force the Headphone output into Mono mode.

The Subwoofer Gain and Frequency Bandwidth values are programmed in registers SW_GAIN and

SW_BAND, respectively. The cut-off frequency can be adjusted from between 50 and 400 Hz in

steps of 50 Hz.

3.9

Beeper

The beeper is used to replace the audio signal with a tone on the Loudspeaker or Headphone

outputs. It can be used for various applications such as beep sounds for remote control, alarm clock

or other features.

Table 7: Headphone/Mute Register Configuration

ANA_LS_HP Register

Output Status

HPD_IN

HPD_ON

SW_ON

MUTE_LS

MUTE_SW

MUTE_HP

Muted

Active

LS, HP Stereo

LS & SW

LS, SW & HP (Channel Change: Mute All)

LS, SW & HP Mono

SW & HP

LS (Default)

SW & LS

HP Stereo

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