AK4145 Datasheet, PDF (14/27 Pages) Asahi Kasei Microsystems – Digital BTSC Stereo Encoder

[AK4145]
■ De-emphasis Filter
A digital de-emphasis filter is built-in (tc = 50/15µs) for pre-emphasized audio data input. Setting the DEM bit “1”
enables the digital de-emphasis filter. In parallel control mode, the de-emphasis filter is always “OFF”
DEM bit De-emphasis Filter
1
ON
0
OFF
(default)
Table 11. De-emphasis Filter Control
■ Soft Mute Operation
When the SMUTE bit is set to “1”, if the volume level was 0dB, the output signal is attenuated to -∞dB in 772 LRCK
cycles. When the SMUTE bit returns to “0”, the mute is cancelled and the attenuation gradually changes to the volume
level. If the soft mute is cancelled before attenuating to the mute state, the attenuation is discontinued and returned to
volume level by the same cycles. The soft mute is effective for changing the signal source without stopping the signal
transmission. In parallel control mode, the soft mute function is not available.
SMUTE bit
Volume level
Gain (at the input of
encoder block)
-∞dB
(1)
(2)
(1)
Notes:
(1) Transition time. 772 LRCK cycles (772/fs) when the volume level is 0dB.
(2) If the soft mute is cancelled before attenuating to -∞, the attenuation is discontinued
and returned to the volume level by the same number of clock cycles.
Figure 6. Soft Mute
MS0982-E-01
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2010/09