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AK4679EG Datasheet, PDF (71/220 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with DSP and MIC/RCV/HP/SPK/LINE-AMP | |||
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[AK4679]
(4) Gain Compensation (EQ0)
Gain Compensation is used to compensate the frequency response and the gain that is changed by Stereo Separation
Emphasis Filter. Gain Compensation is composed with Equalizer (EQ0) and the Gain (0dB/+12dB/+24dB). E0A15-0,
E0B13-0 and E0C15-0 bits set the coefficient of EQ0. GN1-0 bits set the gain (Table 27). EQ0 bit controls ON/OFF of
EQ0. When EQ is OFF and the gain is 0dB, the audio data passes this block by 0dB gain. The coefficient should be set
when EQ0 bit = â0â or PMPFIL bit = â0â. EQ0 starts operation 4/fs(max) after when EQ0 bit = â1â and PMPFIL bit = â1â
are set.
fs: Sampling frequency
fc1: Pole frequency
fc2: Zero-point frequency
K: Filter gain [dB] (Maximum +12dB)
Register setting (Note 77)
E0A[15:0] bits =A, E0B[13:0] bits =B, E0C[15:0] bits =C
(MSB=E0A15, E0B13, E0C15; LSB=E0A0, E0B0, E0C0)
1 + 1 / tan (Ïfc2/fs)
A = 10K/20 x
,
1 + 1 / tan (Ïfc1/fs)
1 â 1 / tan (Ïfc1/fs)
B=
,
1 + 1 / tan (Ïfc1/fs)
1 â 1 / tan (Ïfc2/fs)
C =10K/20 x
1 + 1 / tan (Ïfc1/fs)
Transfer function
H(z) =
A + Cz â1
1 + Bz â1
Gain[dB]
K
fc1
fc2
Frequency
Figure 66. EQ0 Frequency Response
GN1 bit
GN0 bit
Gain
0
0
0dB
(default)
0
1
+12dB
1
x
+24dB
Table 27. Gain select of gain block (x: Donât care)
MS1402-E-06
- 71 -
2013/02
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