SM5843AS1 datasheet(15/24 Pages) NPC

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SM5843A

×1

NIPPON PRECISION CIRCUITS—15

Soft Muting

The muting function controls the muting of both left

and right channels simultaneously. Muting is ON

when MUTE is HIGH, muting is OFF when MUTE

is LOW.

When MUTE goes HIGH, the attenuation changes

smoothly from 0 to

−∞ dB in 512/fs, or approxi-

mately 11.6 ms when fs = 44.1 kHz. When MUTE

goes LOW, muting is released and the attenuation

changes smoothly from

−∞ to 0 dB, again taking

approximately 11.6 ms.

When RSTN goes LOW, the DOL and DOR outputs

go LOW, immediately muting the output signal.

Muting is released and timing is synchronized imme-

diately after RSTN goes HIGH.

Digital Attenuator (MDT, MCK, MLEN)

The attenuation function is controlled by MDT,

MCK and MLEN. MDT data, in 11-bit serial MSB

ﬁrst format, is shifted into an internal shift register

on the rising edge of the serial data clock MCK. The

contents of the shift register are transferred to the

internal processing circuits on the rising edge of the

MLEN gate pulse. The attenuation data format is

shown in ﬁgure 3.

The attenuation register data DATT can take on any

value between 0 and 1024 (400H). The attenuation is

given by the following equation for both left and

right channels simultaneously.

Attenuation = 20

× log

10(DATT/1024) [dB]

Thus, the attenuation level is

−∞ when DATT is 0,

and attenuation is 0 dB when DATT is 1024. DATT

is set to 1024 (400H) after system reset initialization.

The attenuation data and attenuation level for sample

DATT values are shown in the following table.

Figure 2. Mute timing

MUTE

0dB

(Gain)

−∞

512 / fs

Figure 3. Attenuation data format

B9 B10 B11

a10

MSB

LSB

MDT

MCK

MLEN

Attenuation data DATT

Attenuation level (dB)

000H

−∞

001H

3FFH

−60.206

−0.0085

400H

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