AK4637EN Datasheet, PDF (47/96 Pages) Asahi Kasei Microsystems – 24bit Mono CODEC with MIC/SPK-AMP

[AK4637]
Transfer Function
H(z) = {1 + G₂ x h₂(z) + G₃ x h₃(z) + G₄ x h₄(z) + G₅ x h₅(z)} x {1+ h₁(z) }
(G_{2, 3, 4, 5} = 1 or G)
h_n (z) = A_n
1  z ^2
1 B_nz ^1 C_nz ^2
(n = 1, 2, 3, 4, 5)
The center frequency must be set as below.
0.003 < fo_n / fs < 0.497
When gain of K is set to “1”, this equalizer becomes a notch filter. When EQ2 EQ5 is used as a notch
filter, central frequency of a real notch filter deviates from the above-mentioned calculation, if its central
frequency of each band is near. The control soft that is attached to the evaluation board has functions that
revises a gap of frequency and calculates the coefficient. When its central frequency of each band is near,
the central frequency should be revised and confirm the frequency response.
Note 33. [Translation the filter coefficient calculated by the equations above from real number to binary
code (2’s complement)]
X = (Real number of filter coefficient calculated by the equations above) x 2¹³
X should be rounded to integer, and then should be translated to binary code (2’s complement).
MSB of each filter coefficient setting register is sine bit.
IN
OUT
EQ2
EQC2 bit = “0”
EQ3
EQC2 bit = “1”
EQ2 Gain (EQ2G5-0 bits)
EQC3 bit = “0”
EQ4
EQC3 bit = “1”
EQ3 Gain (EQ3G5-0 bits)
EQC4 bit = “0”
EQ5
EQC4 bit = “1”
EQ4 Gain (EQ4G5-0 bits)
EQC5 bit = “0”
EQC5 bit = “1”
EQ5 Gain (EQ5G5-0 bits)
Figure 44. 4-Band EQ Structure
015010680-E-00
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2015/09