MSP3410D datasheet(49/83 Pages) MICRONAS

49 / 83 page

PRELIMINARY DATA SHEET

MSP 34x0D

Micronas

The absolute value of the incoming signal is fed into a

filter with 16 ms attack time and selectable decay time.

The decay time must be adjusted as shown in the

table above. This attack/decay filter block works simi-

lar to a peak hold function. The volume correction

value with its quasi continuous step width is calculated

using the attack/decay filter output.

The Automatic Volume Correction functions with an

internal reference level of

−18 dBr. This means that

input signals with a volume level of

−18 dBr will not be

affected by the AVC. If the input signals vary in a range

−24 dB to 0 dB, the AVC maintains a fixed output

level of

−18 dBr.

Fig. 7–1 shows the AVC output level versus its input

level. For prescale and volume registers set to 0 dB, a

level of 0 dBr corresponds to full scale input / output.

This is

– SCART in-, output 0 dBr

= 2.0 V

rms

– Loudspeaker and Aux output 0 dBr

= 1.4 V

rms

Fig. 7–1: Simplified AVC characteristics

To reset the internal variables, the AVC should be

switched off and on during any channel or source

change. For standard applications, the recommended

decay time is 4 sec.

Note: AVC should not be used in any Dolby Pro Logic

mode, except PANORAMA, where no other than the

loudspeaker output is active.

7.3.24. Subwoofer Channel

The subwoofer channel is created by combining the left

and right channels directly behind the tone control filter

block. A third order low-pass filter with programmable

corner frequency and volume adjustment according to

the main channel output is performed to the bass sig-

nal. Additionally, at the loudspeaker channels, a com-

plementary high-pass filter can be switched on.

−30

−24

−18

−12

−6

input level

−18

−24

−12

output level

[dBr]

Subwoofer Channel

Volume Adjust

002Chex

0 dB

0000 0000

00hex

RESET

−1 dB

1111 1111

FFhex

−29 dB

1110 0011

E3hex

−30 dB

1110 0010

E2hex

Mute

1000 0000

80hex

Subwoofer Channel

Corner Frequency

002Dhex

50 Hz ... 400 Hz

e.g. 50 Hz = 5dec

400 Hz = 40dec

RESET

00hex

0000 0101

05hex

0010 1000

28hex

Subwoofer: Comple-

mentary High-pass

002Dhex

HP off

0000 0000

00hex

RESET

HP on

0000 0001

01hex

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