ak4648 AKM Semiconductor, Inc., ak4648 Datasheet - Page 47

• Manufacturer Part Number: ak4648
• Description: Stereo Codec With Mic/hp/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

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The AK4648 performs wind-noise reduction filter, stereo separation emphasis, gain compensation and ALC (Automatic
Level Control) by digital domain for A/D converted data (Figure 34). 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.
PMADL bit, PMADR bit PMDAC bit LOOP bit
FIL3 coefficient also sets the attenuation of the stereo separation emphasis.
The combination of GN1-0 bit (Table 25) 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”.
MS0625-E-01
Digital EQ/HPF/LPF
Wind-noise reduction
01, 10 or 11
An y coefficient
F1A13-0
F1B13-0
00
F1AS
FIL1
Note 55. Stereo separation emphasis circuit is effective only at stereo operation.
An y coefficient
Table 24. Digital EQ/HPF/LPF Circuit Setting (x: Don’t care)
F3A13-0
F3B13-0
F3AS
0
1
0
1
Stereo separation emphasis
GN1
Table 25. Gain select of gain block (x: Don’t care)
0
0
1
FIL3
0dB ∼ -10dB
MUTE
(set by
Figure 34. Digital EQ/HPF/LPF
FIL3 coefficient)
x
x
x
0
1
GN0
0
1
x
Recording Monitor Playback
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Recording & Playback
Power-down
Recording
Playback
Status
+12dB
+24dB
An y coefficient
+12dB ∼ 0dB
Gain
0dB
EQC15-0
EQA15-0
EQB13-0
Gain compensation
EQ
(default)
+24/+12/0dB
Digital EQ/HPF/LPF
GN1-0
Gain
Recording path
Recording path
Recording path
Playback path
Power-down
ALC
[AK4648]
(default)
2007/06
st