ak4644 AKM Semiconductor, Inc., ak4644 Datasheet - Page 41

• Manufacturer Part Number: ak4644
• Description: Stereo Codec With Mic/hp/rcv-amp
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
3) EQ
[Translation the filter coefficient calculated by the equations above from real number to binary code (2’s complement)]
[Filter Coefficient Setting Example]
1) FIL1 block
2) EQ block
MS0477-E-01
fs: Sampling frequency
fc
fc
f: Input signal frequency
K: Filter gain [dB] (Maximum +12dB)
Register setting
X = (Real number of filter coefficient calculated by the equations above) x 2
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.
Example: HPF, fs=44.1kHz, fc=100Hz
F1AS bit = “0”
F1A[13:0] bits = 01 1111 1100 0110
F1B[13:0] bits = 10 0000 0111 0100
Example: fs=44.1kHz, fc
EQA[15:0] bits = 0000 1001 0110 1110
EQB[13:0] bits = 10 0001 0101 1001
EQC[15:0] bits = 1111 1001 1110 1111
H(z) =
1
2
Transfer function
: Pole frequency
: Zero-point frequency
EQA[15:0] bits =A, EQB[13:0] bits =B, EQC[15:0] bits =C
(MSB=EQA15, EQB13, EQC15; LSB=EQA0, EQB0, EQC0)
Gain[dB]
A = 10
+8dB
A + Cz
1 + Bz
K/20
x
−1
−1
1 + 1 / tan (πfc
1 + 1 / tan (πfc
1
=300Hz, fc
M(f) =
fc
1
2
1
/fs)
/fs)
A
2
=3000Hz, Gain=+8dB
1 + B
2
Amplitude
,
+ C
fc
2
2
2
B =
+ 2ACcos (2πf/fs)
+ 2Bcos (2πf/fs)
1 − 1 / tan (πfc
1 + 1 / tan (πfc
- 41 -
Frequency
1
1
/fs)
/fs)
θ(f) = tan
,
C =10
13
−1
K/20
A + BC + (AB+C)cos (2πf/fs)
x
(AB−C)sin (2πf/fs)
Phase
1 − 1 / tan (πfc
1 + 1 / tan (πfc
2
1
/fs)
/fs)
[AK4644]
2006/10