AK4951AEN Datasheet, PDF (46/105 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/HP/SPK-AMP

[AK4951A]
(4) Gain Compensation (EQ0)
Gain compensation is used to compensate the frequency response and the gain that is changed by the
stereo separation emphasis filter. Gain compensation is composed of the Equalizer (EQ0) and the Gain
(0dB/+12dB/+24dB). E0A15-0 bits, E0B13-0 bits and E0C15-0 bits set the coefficient of EQ0. GN1-0 bits
set the gain (Table 31). 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 = “0” or PMPFIL bit = “0”.
The EQ0 starts operation 4/fs(max) after when EQ0 bit =PMPFIL bit= “1” is set.
fs: Sampling Frequency
fc₁: Polar Frequency
fc₂: Zero-point Frequency
K: Gain [dB] (Maximum setting is +12dB.)
Register Setting (Note 37)
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 (fc₂/fs)
A = 10^K/20 x
,
1 + 1 / tan (fc₁/fs)
1  1 / tan (fc₁/fs)
B=
,
1 + 1 / tan (fc₁/fs)
1  1 / tan (fc₂/fs)
C =10^K/20 x
1 + 1 / tan (fc₁/fs)
Transfer Function
H(z) =
A + Cz ^1
1 + Bz ^1
Gain[dB]
K
fc₁
fc₂
Frequency
(Note) Black: Diagrammatic Line, Red: Actual Curve
Figure 35. EQ0 Frequency Response
Table 31. Gain Setting
GN1 bit
GN0 bit
Gain
0
0
0dB
0
1
+12dB
1
x
+24dB
(x: Do not care)
(default)
016001936-E-00
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2016/03