SM5849F datasheet(18/26 Pages) NPC

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SM5849AF

NIPPON PRECISION CIRCUITS—18

Attenuator operation

A change in the attenuation data DATT causes the

gain to change smoothly from its previous value

towards the new setting. The new attenuation data is

stored in the attenuation data register and the current

attenuation level is stored in a temporary register.

Consequently, if a new attenuation level is read in

before the previously set level is reached, the gain

changes smoothly from the current value towards the

latest setting as shown in ﬁgure 4.

The attenuation counter output changes, and hence

the gain changes, by 1 step every output sample. The

time taken to reduce the gain from 0dB (or 12dB) to

−∞dB is (1024/fso), which corresponds to approxi-

mately 23.2ms when fso = 44.1kHz.

Mute (DMUTE)

Direct mute

Other mute operations

The direct mute function is also invoked at the fol-

lowing times.

When the reset input (RSTN) changes.

When the fs setting changes, for deemphasis,

using either FSI1, FSI2 inputs or FFSI1, FFSI2

ﬂags.

When the ICKSL, IFM1, or IFM2 setting changes.

When the ICLK input system clock stops.

Figure 4. Attenuator operation example

Level 3

Level 1

Level 2

Level 4

Level 5

Time

Gain

∆t

0 dB

—

∞

Table 7. DMUTE operation ON/OFF

DMUT

Function

LO W

N o r mal data is output from the next output word (mute

OFF)

HIGH

0 data is output from the next output word (mute ON)

Table 8. Other mute operations

Input

Function

RSTN = LOW

0 data is output from the next

output word (mute ON)

RSTN = HIGH

N o r mal data is output from the

3073rd output word (mute OFF)

FSI1, FSI2 input settings

changed (MCOM = LOW).

FFSI1, FFSI2 input settings

changed (MCOM = HIGH)

0 data is output from the next

output word (mute ON).

N o r mal data is output from the

3073rd output word (mute OFF)

ICKSL, IFM1, IFM2 input

settings change.

ICLK input system clock stops.

0 data is output from the next

output word (mute ON)

ICLK input system clock

restarts.

N o r mal data is output from the

3073rd output word (mute OFF)

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