ak4644 AKM Semiconductor, Inc., ak4644 Datasheet - Page 39

• Manufacturer Part Number: ak4644
• Description: Stereo Codec With Mic/hp/rcv-amp
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
The AK4644 performs wind-noise reduction filter, stereo separation emphasis, gain compensation and ALC (Automatic
Level Control) by digital domain for A/D converted data (Figure 35). FIL1, FIL3 and EQ blocks are IIR filters of 1
order. The filter coefficient of FIL3, EQ and FIL1 blocks can be set to any value. Refer to the section of “ALC operation”
about ALC.
When only DAC is powered-up, digital EQ/HPF/LPF circuit operates at playback path. When only ADC is powered-up
or both ADC and DAC are powered-up, digital EQ/HPF/LPF circuit operates at recording path. Even if the path is
switched from recording to playback, the register setting of filter coefficient at recording remains. Therefore, FIL3, EQ,
FIL1 and GN1-0 bits should be set to “0” if digital EQ/HPF/LPF is not used for playback path.
FIL3 coefficient also sets the attenuation of the stereo separation emphasis.
The combination of GN1-0 bit (Table 26) and EQ coefficient set the compensation gain.
FIL1 and FIL3 blocks become HPF when F1AS and F3AS bits are “0” and become LPF when F1AS and F3AS bits are
“1”, respectively.
When EQ and FIL1 bits are “0”, EQ and FIL1 blocks become “through” (0dB). When FIL3 bit is “0”, FIL3 block become
“MUTE”. When each filter coefficient is changed, each filter should be set to “through” (“MUTE” in case of FIL3).
When MIX bit = “1”, only FIL1 is available. In this case, EQ and FIL3 bits should be set to “0”.
MS0477-E-01
PMADL bit, PMADR bit
Digital EQ/HPF/LPF
Wind-noise reduction
“01”, “10” or “11”
An y coefficient
F1A13-0
F1B13-0
“00”
F1AS
FIL1
Note 37. Stereo separation emphasis circuit is effective only at stereo operation.
An y coefficient
Table 25. Digital EQ/HPF/LPF Cirtcuit Setting (x: Don’t care)
PMDAC bit
F3A13-0
F3B13-0
F3AS
Stereo separation emphasis
0
1
0
1
GN1
Table 26. Gain select of gain block (x: Don’t care)
0
0
1
FIL3
LOOP bit
0dB ∼ -10dB
MUTE
(set by
Figure 35. Digital EQ/HPF/LPF
FIL3 coefficient)
x
x
x
0
1
GN0
0
1
x
Recording Monitor Playback
- 39 -
Recording & Playback
Power-down
Recording
Playback
+12dB
+24dB
Status
An y coefficient
+12dB ∼ 0dB
Gain
0dB
EQC15-0
EQA15-0
EQB13-0
Gain compensation
EQ
Default
+24/+12/0dB
GN1-0
Digital EQ/HPF/LPF
Gain
Recording path
Recording path
Recording path
Playback path
Power-down
ALC
[AK4644]
2006/10
Default
st