SM5843A×1
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.
MUTE
L
H
L
0dB
(Gain)
−∞
512 / fs
512 / fs
Figure 2. Mute timing
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.
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11
MDT
MCK
a0
a1 a2 a3 a4 a5
a6 a7 a8 a9 a10
LSB
MSB
MLEN
Figure 3. Attenuation data format
The attenuation register data DATT can take on any
Attenuation data DATT
000
Attenuation level (dB)
value between 0 and 1024 (400 ). The attenuation is
given by the following equation for both left and
right channels simultaneously.
H
−∞
H
001
−60.206
to
H
to
3FF
−0.0085
Attenuation = 20 × log (DATT/1024) [dB]
H
10
400
0
H
Thus, the attenuation level is −∞ when DATT is 0,
and attenuation is 0 dB when DATT is 1024. DATT
is set to 1024 (400 ) after system reset initialization.
H
The attenuation data and attenuation level for sample
DATT values are shown in the following table.
NIPPON PRECISION CIRCUITS—15
NPC [ NIPPON PRECISION CIRCUITS INC ]
