AK4950 Datasheet, PDF (46/106 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP & mini DSP

[AK4950]
GN1 bit
GN0 bit
Gain
0
0
0dB
(default)
0
1
+6dB
1
0
+12dB
1
1
+24dB
Table 26. Gain Select of the Gain Block
Setting Example) Gain Compensation EQ0: High-boost, fs=44.1kHz, fc= 3.5kHz, Q= 0.7071 (Gain =+3dB) (I²C mode)
A0 =1565F1 (hex): Addr. 99H
A1 =E1A168 (hex): Addr. 9AH
A2 = 0C79DC (hex): Addr. 9BH
B1 = 14FCF9 (hex): Addr. 9CH
B2 = F781D1 (hex): Addr. 9DH
(3) 3-band Equalizer & 1-band Equalizer after ALC
This block can be used as equalizer or Notch Filter. 3-band equalizer (EQ2, EQ3, and EQ4) is switched ON/OFF
independently by EQ2, EQ3, and EQ4 bits. ON/OFF switching of the equalizer after ALC (EQ1) is controlled by
coefficients. When the equalizer is OFF, the audio data passes this block by 0dB gain. Address 6BH ~ 6FH (3-wire mode,
COEW bit = “1”) and address EBH~EFH (I²C mode) set the coefficient of EQ1. Address 20H ~ 26H(3-wire mode,
COEW bit = “1”) and address A0H~A6H (I²C mode) set the coefficient of EQ2. Address 29H ~ 2FH(3-wire mode,
COEW bit = “1”) and address A9H~AFH (I²C mode) set the coefficient of EQ3. Address 32H ~ 36H(3-wire mode,
COEW bit = “1”) and address B2~B6H (I²C mode) set the coefficient of EQ4. The EQx (x=1, 2, 3 or 4) coefficient must
be set when PMPFIL bit = “0”. EQ1-4 start operation 2/fs(max) after when EQx (x=1, 2, 3 or 4) = PMPFIL bit = “1” is set.
1) When EQ1 ~ EQ4 = Notch Filter
fs: Sampling Frequency
fo: Center Frequency
α = sin(2πfc/fs) / 2Q
A = boost gain Example) Boost gain = +12dB (A = 10 ^{Gain [dB] / 40} ) when A=2
Q = fo/BW (BW: Band Width)
1
A0 = A2 = _{1 + α}
A1 =
–2 cos (2πfc/fs)
1+α
B1 =
2 cos (2πfc/fs)
1 +α
1– α
B2 = – _{1+ α}
The cut-off frequency must be set as below.
EQ1, EQ4: 0.0625 < fo_n / fs < 0.497
EQ2, EQ3: fo_n / fs < 0.497
MS1320-E-00
- 46 -
2011/10