AK4561 Datasheet, PDF (31/48 Pages) Asahi Kasei Microsystems – 16bit CODEC with built-in ALC and MIC/HP-Amp

ASAHI KASEI
AKM CONFIDENTIAL
[AK4561]
1. Pre-Amp
Pre-Amp is non-inverting amplifier and internally biased to MVCM voltage with 100kΩ (typ.). Gain value of Pre-Amp is
adjusted by S6-5 bits. Their value is +12dB∼+24dB and 4dB step.
Input impedance is changed by the set of gain. Input impedance value is precision in typ±30%.
S6 S5
0
0
0
1
1
0
1
1
Gain
+12dB
+16dB
+20dB
+24dB
Ri (typ)
2.4kΩ
1.5kΩ
950Ω
600Ω
RESET
An external capacitor needs to cancel DC gain. Cut-off frequency is decided by internal input resistor (Ri) and an external
capacitor (C).
INT_MIC
EXT_MIC
Ci
Ri
-
+
Pre Amp
Figure 13. Pre-Amp Block
2. EQ-Amp
EQ-Amp is block to emphasize a stereo feeling at using Internal MIC Mode. EQ-Amp can be emphasized by adding the
output signal from pre-amplifier and the opposite channel differentially.
When External MIC Mode is selected, EQ-Amp does not connect.
Power ON/OFF of EQ-Amp and Inverter-Amp is enabled by EQ bit. When EQ bit is “1”, they can be ON/OFF by PM0
bit. When EQ bit is “0”, these amplifiers are OFF then PM0 bit is not relative.
3. HPF-Amp
To cancel wind-noise, AK4561 has the HPF-Amp which is non-inverting amplifier, 2^nd order high pass filter and gain of
0dB. The HPF-Amp can be ON/OFF by controlling the internal registers. In case of OFF, HPF-Amp becomes a unity gain
buffer. This HPF-Amp can use when Internal MIC Mode is selected. In case of External MIC Mode, the control of
HPF-Amp is invalid and becomes a unity gain buffer.
4. Power Supply for MIC
Power Supply for microphone is supplied from MPWR pin. Output voltage is typically 2.0V and MPWR pin can supply
the current until 3mA.
When PM0 bit is “0”, the power supply current can be stopped.
Rev. 0.9
- 31 -
2000/09