AK4649 Datasheet, PDF (55/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
■ De-emphasis Filter
The AK4649 includes a digital de-emphasis filter (tc = 50/15μs) which corresponds 3 kinds frequency (32kHz, 44kHz,
48kHz) by IIR filter. Setting the DEM1-0 bits enables the de-emphasis filter (Table 47).
DEM1
0
0
1
1
DEM0
Mode
0
44.1kHz
1
OFF
0
48kHz
1
32kHz
Table 47. De-emphasis Control
(default)
■ Soft Mute
Soft mute operation is performed in the digital domain. When the SMUTE bit is set “1”, the output signal is attenuated to
-∞ in“ATT_DATA/fs” cycle. When the SMUTE bit is returned to “0”, the mute is cancelled and the output attenuation
gradually changes to 0dB in “ATT_DATA/fs” cycle. If the soft mute is cancelled within this cycle after starting an
operation, the attenuation is discontinued and it is returned to 0dB by the same cycle. Soft mute is effective for changing
the signal source without stopping the signal transmission at playback path.
SMUTE bit
ATT_DATA
(1)
A tte n u a tio n
(1)
(3)
-∞
Analog O utput
GD
GD
(2)
Figure 37. Soft Mute Function
(1) The input signal is attenuated by −∞ (“0”) during “ATT_DATA/fs” cycle (when ATT_DATA = 0dB, 255/fs =
5.7msec@fs=44.1kHz).
(2) Analog output corresponding to digital input has group delay (GD).
(3) If soft mute is cancelled before attenuating to −∞, the attenuation is discounted and returned to ATT_DATA value
within the same cycle.
MS1023-E-01
- 55 -
2010/08