SM5877AM datasheet(14/16 Pages) NPC

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SM5877AM

NIPPON PRECISION CIRCUITS—14

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.

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.

Gain

DATT

----------------





log

[dB]

Soft Mute (SMUTE)

Table 2. Attenuator gain

DATT

Gain (dB)

DATT

Gain (dB)

DATT

Gain (dB)

DATT

Gain (dB)

0.0

−2.545

−6.160

−12.465

−0.139

−2.732

−6.444

−13.064

−0.280

−2.923

−6.739

−13.708

−0.424

−3.118

−7.044

−14.403

−0.570

−3.317

−7.360

−15.159

−0.718

−3.522

−7.687

−15.987

−0.869

−3.731

−8.028

−16.902

−1.023

−3.946

−8.383

−17.925

−1.180

−4.166

−8.752

−19.085

−1.339

−4.391

−9.138

−20.424

−1.501

−4.623

−9.542

−22.007

−1.667

−4.861

−9.966

−23.946

−1.835

−5.105

−10.412

−26.444

−2.007

−5.357

−10.881

−29.966

−2.183

−5.617

−11.378

−35.987

−2.362

−5.884

−11.904

−∞

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.

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

shown

ﬁgure

Upon system initialization or when MODE changes

state, mute is released, which corresponds to the

maximum gain of 0 dB.

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