SM5877 Nippon Precision Circuits Inc, SM5877 Datasheet - Page 14

• Manufacturer Part Number: SM5877
• Description: 3rd-order / 2-channel D/A Converter
• Manufacturer: Nippon Precision Circuits Inc

Table 2. Attenuator gain
Soft Mute (SMUTE)
Soft mute mode is selected when MODE is HIGH.
The up/down counter is switched to internal clock
drive, and soft mute operation is controlled by
MUTE only.
When MUTE goes HIGH, the up/down counter
counts down. The total time to go from 0 to maxi-
mum mute is 1024/fs. This corresponds to approxi-
mately 23.2 ms at fs = 44.1 kHz.
Deemphasis Filter (DEEM)
The built-in digital deemphasis filter is designed to
operate at 44.1 kHz. Deemphasis is ON when DEEM
is HIGH, and OFF when DEEM is LOW.
Attenuation (MDT, MCK, MLEN)
The digital attenuation mode is selected when
MODE is LOW. The attenuator operates by multi-
plying the internal 6-bit up/down counter’s output
data with the signal data.
The direction of the 6-bit up/down counter is con-
trolled by the level on MUTE (down when MUTE is
HIGH, and up when MUTE is LOW). The count is
advanced on the rising edge of ATCK.
When the count reaches 0 (down) or 63 (up), the
counter automatically stops.
DATT
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
Gain (dB)
0.139
0.280
0.424
0.570
0.718
0.869
1.023
1.180
1.339
1.501
1.667
1.835
2.007
2.183
2.362
0.0
DATT
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
Gain (dB)
2.545
2.732
2.923
3.118
3.317
3.522
3.731
3.946
4.166
4.391
4.623
4.861
5.105
5.357
5.617
5.884
SM5877AM
The gain is set by the counter contents DATT as fol-
lows.
Upon system initialization or when MODE changes
state, DATT is set to 63, which corresponds to the
maximum gain of 0 dB as shown in table 2.
When MUTE is LOW, soft mute is released. The
attenuation counter output counts up, increasing the
gain. The time taken to return to 0 dB is also 1024/fs.
Soft mute operation is shown in figure 2.
Upon system initialization or when MODE changes
state, mute is released, which corresponds to the
maximum gain of 0 dB.
DATT
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Gain
=
Gain (dB)
20
10.412
10.881
11.378
11.904
6.160
6.444
6.739
7.044
7.360
7.687
8.028
8.383
8.752
9.138
9.542
9.966
NIPPON PRECISION CIRCUITS—14
log
DATT
--------------- -
63
DATT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
[dB]
Gain (dB)
12.465
13.064
13.708
14.403
15.159
15.987
16.902
17.925
19.085
20.424
22.007
23.946
26.444
29.966
35.987