AK4691 Datasheet, PDF (45/80 Pages) Asahi Kasei Microsystems – 4ch ADC + 2ch DAC with MIC/HP/SPK-AMP

[AK4691]
■ FADEOUT Mode
In FADEOUT mode, the present IVL/R values decrease gradually down to the MUTE state when FDOUT bit changes
from “0” to “1”. The operation is executed by the zero crossing detection. If the large signal is supplied to the ALC circuit
during the FADEOUT operation, the ALC limiter operation starts. However, the total time of the FADEOUT operation is
the same time, even if the limiter operation is executed. The period of FADEOUT is set by FDTM1-0 bits (Table 34), the
number of step is set by FDATT1-0 bits (Table 35). When FDOUT bit changes into “0” during the FADEOUT operation,
the ALC operation starts from the present IVL/R values. When FDOUT and ALC bits change into “0” at the same time,
the FADEOUT operation stops and the IVL/R keeps the value at that time.
NOTE: When FDIN and FDOUT bits are set to “1” at the same time, FADEOUT operation is prior to FADEIN operation.
SDTO1, 2
IVL/R7-0 bits
00H
XXH
ALC bit
FDOUT bit
(2)
(1)
(3) (4) (5) (6) (7) (8) (9)
Figure 28. Example for controlling sequence in FADEOUT operation
(1) WR (FDOUT bit = “1”): The FADEOUT operation starts. Then ALC bit should be always “1”.
(2) FADEOUT time is set by REF7-0, FDTM1-0 and FDATT bits.
e.g. REF7-0 = E1H(225 dec), FDTM1-0 = “01” (= 42.7ms @ fs = 48kHz), FDATT1-0 = 2 step
(225 x FDTM1-0) / FDATT1-0 = 225 x 42.7ms / 2 = 4.8s
(3) The FADEOUT operation is completed. The IVL/R values are the MUTE state. If FDOUT bit keeps “1”, the IVL/R
values keep the MUTE state.
(4) Analog and digital outputs are muted externally. Then the IVL/R values are MUTE state.
(5) WR (IVL/R7-0 bits = 00H) : IVL/R are changed to “MUTE”.
(6) WR (ALC bit = FDOUT bit = “0”): Exit the ALC and FADEOUT operations
(7) WR (IVL/R7-0 bits = XXH): The IVL/R value should be set to the same or smaller than REF’s.
(8) WR (ALC bit = “1”, FDOUT bit = “0”): The ALC operation restarts. But the ALC bit should be written until
completing zero crossing detection operation of IVL/R.
(9) Release an external mute function for analog and digital outputs.
MS0672-E-00
- 45 -
2007/11