MAS3587F datasheet(9/82 Pages) MICRONAS

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ADVANCE INFORMATION

MAS 3587F

Micronas

2.5.2. Program Download Feature

The standard functions of the MAS 3587F can be

extended or substituted by downloading up to 4kWords

(1 Word = 20 bits) of program code and additionally up

to 4kWords of coefficients into the internal RAM.

The code must be downloaded by the Fast Program

Download

command

(see

Section

3.3.1.14.

page 31) into an area of RAM that is switchable from

data memory to program memory. A Run command

(see Section 3.3.1.1. on page 25) starts the operation.

2.6. 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

2.7. 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.

2.7.1. Baseband Processing

The several baseband functions are applied to the dig-

ital audio signal immediately before D/A conversion.

2.7.1.1. Bass, Treble, and Loudness

Standard baseband functions such as bass, treble,

and loudness are provided (refer to Table 3–12 on

page 43 for details).

2.7.2. Micronas Dynamic Bass (MDB)

The Micronas Dynamic Bass system (MDB) was

developed to extend the frequency range of loud-

speakers or headphones below the cutoff frequency of

the speakers. In addition to dynamically amplifying the

low frequency bass signals, the MDB exploits the psy-

choacoustic phenomenon of the ‘missing fundamen-

tal’. Adding harmonics 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

MDB, it can be customized to create different bass

effects and adapted to various loudspeaker character-

istics (see Section 3.4.4. on page 49).

2.7.2.1. 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 achieve a comfortable listening enjoyment.

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 3–12 on page 43).

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

Mic-In

Line-In

Mono

Mixer

Mono/Stereo

AVC

Bass/Treble

Loudness

Right invert

Volume

Balance

Audio

Codec

Mic-Amplifier incl. Bias

Output

MDB

Q-peak

−30

−24

−18

−12

−6

input level

−15

−21

−9

output level

dBr

OFF

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