[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 = “0” or PMPFIL bit = “0”. EQ0 starts operation 4/fs(max) after when EQ0 bit = “1” and PMPFIL bit = “1”
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 (πfc2/fs)
1 + 1 / tan (πfc1/fs)
1 − 1 / tan (πfc1/fs)
1 + 1 / tan (πfc1/fs)
1 − 1 / tan (πfc2/fs)
1 + 1 / tan (πfc1/fs)
A = 10K/20
x
,
B =
,
C =10K/20 x
Transfer function
A + Cz −
H(z) =
1
1 + Bz −1
Gain[dB]
K
fc1
fc2
Frequency
Figure 66. EQ0 Frequency Response
GN1 bit
GN0 bit
Gain
0dB
+12dB
+24dB
0
0
1
0
1
x
(default)
Table 27. Gain select of gain block (x: Don’t care)
MS1402-E-06
2013/02
- 71 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
