ASAHI KASEI

[AK4342]

MS0506-E-02

2006/07

- 21 -

Soft Mute

Soft mute operation is performed in the digital domain of the DAC input. When the SMUTE bit goes to “1”, the output

signal is attenuated by

−∞ during ATT_DATA×ATT transition time (Figure 16) from the current ATT level. When

SMUTE bit is returned to “0”, the mute is cancelled and the output attenuation gradually changes to the ATT level during

ATT_DATA

×ATT transition time. If the soft mute is cancelled before attenuating to −∞ after starting the operation, the

attenuation is discontinued and returned to ATT level by the same cycle. The soft mute is effective for changing the signal

source without stopping the signal transmission.

SMUTE bit

Attenuation

STS1-0 bits

ATT Level

-

∞

Analog Output

GD

GD

(1)

(2)

(3)

STS1-0 bits

(1)

Figure 16. Soft Mute Function

Notes:

(1) ATT_DATA

×ATT transition time. For example, this time is 510LRCK cycles at normal speed mode and STS1-0

bit = “01” and ATT_DATA = “128”.

(2) Analog output corresponding to digital input has group delay (GD).

(3) If the soft mute is cancelled before attenuating to

−∞ after starting the operation, the attenuation is discontinued

and returned to ATT level by the same cycle.

De-emphasis Filter

The AK4342 includes a digital de-emphasis filter (tc = 50/15

µs) via an IIR filter. This filter corresponds to three

frequencies (32kHz, 44.1kHz and 48kHz). This setting is done via control register (DEM1-0 bits). (See Table 8). When

the AK4342 is half speed mode or double speed mode, the DEM1-0 bits are ignored and the de-emphasis filter is disabled.

DEM1 bit

DEM0 bit

De-emphasis

0

0

44.1kHz

0

1

OFF

Default

1

0

48kHz

1

1

32kHz

Table 8. De-emphasis Filter Frequency control