MAS3549F datasheet(10/92 Pages) MICRONAS

10 / 92 page

MAS 35x9F

DATA SHEET

June 30, 2004; 6251-505-1DS

Micronas

2.4. Audio Codec

A sophisticated set of audio converters and sound fea-

tures has been implemented to comply with various

kinds of operating environments that range up to high-

end equipment (see Fig. 2–4).

Fig. 2–4: Signal flow block diagram of Audio Codec

2.4.1. A/D Converter and Microphone Amplifier

A pair of A/D converters is provided for recording or

loop-through purposes. In addition, a microphone

amplifier including voltage supply function for an elec-

tret type microphone has been integrated.

2.4.2. Baseband Processing

The several baseband functions are applied to the dig-

ital audio signal immediately before D/A conversion.

2.4.2.1. Bass, Treble, and Loudness

Standard baseband functions such as bass, treble,

and loudness are provided (refer to Table 3–16 for

details).

2.4.2.2. Micronas Bass (MB)

The Micronas Bass system (MB) was developed to

extend the frequency range of loudspeakers or head-

phones below the cutoff frequency of the speakers.

Apart from dynamically amplifying the low-frequency

bass signals, the MB exploits the psycho-acoustic phe-

nomenon of the ‘missing fundamental’. Adding har-

monics of the frequency components below the cutoff

frequency gives the impression of actually hearing the

low frequency fundamental, while at the same time

retaining the loudness of the original signal. Due to the

parametric implementation of the MB, it can be cus-

tomized to create different bass effects and adapted to

various

loudspeaker

characteristics

(see

Section 3.4.4. and Table 3–16).

2.4.2.3. Automatic Volume Control (AVC)

In a collection of tracks from different sources fairly

often the average volume level varies. Especially in a

noisy listening environment the user must adjust the

volume to comfortably enjoy listening. The Automatic

Volume Correction (AVC) solves this problem by

equalizing the volume level.

To prevent clipping, the AVC's gain decreases quickly

in dynamic boost conditions. To suppress oscillation

effects, the gain increases rather slowly for low level

inputs. The decay time is programmable by means of

the AVC register (see Table 3–16 on page 46).

For input levels of -18 dBr to 0 dBr, the AVC maintains

a fixed output level of -9 dBr. Fig. 2–5 shows the AVC

output level versus its input level. For volume and

baseband registers set to 0 dB, a level of 0 dBr corre-

sponds to full scale input/output.

Fig. 2–5: Simplified AVC characteristics

2.4.2.4. Balance and Volume

To minimize quantization noise, the main volume con-

trol is automatically split into a digital and an analog

part. The volume range is

−114...+12 dB with an addi-

tional mute position. A balance function is provided.

Mic-In

Line-In

Mono

Mixer

Mono/Stereo

AVC

Bass/Treble

Loudness

Right invert

Volume

Balance

Audio

Codec

Mic-Amplifier incl. Bias

Output

Q-peak

−30

−24

−18

−12

−6

input level

−15

−21

−9

output level

dBr

AVCoff

AVCon

MAS3549F датащи(PDF) 10 Page - Micronas

MAS3549F датащи(HTML) 10 Page - Micronas

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92

датащи скачать

ссылки URL