AK4691EG AKM [Asahi Kasei Microsystems], AK4691EG Datasheet - Page 38

• Manufacturer Part Number: AK4691EG
• Description: 4ch ADC + 2ch DAC with MIC/HP/SPK-AMP
• Manufacturer: AKM [Asahi Kasei Microsystems]

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) FIL1Ablock
2) EQA block
MS0672-E-00
fs: Sampling frequency
fc
fc
f: Input signal frequency
K: Filter gain [dB] (Maximum +12dB)
Register setting for ADC1
Register setting for ADC2
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
F1ASAbit = “0”
F1A[13:0]A bits = 01 1111 1100 0110
F1B[13:0]A bits = 10 0000 0111 0100
Example: fs=44.1kHz, fc
EQA[15:0]A bits = 0000 1001 0110 1110
EQB[13:0]A bits = 10 0001 0101 1001
EQC[15:0]A bits = 1111 1001 1110 1111
H(z) =
1
2
Transfer function
: Pole frequency
: Zero-point frequency
EQA[15:0]A bits =A, EQB[13:0]A bits =B, EQC[15:0]A bits =C
(MSB=EQA15A, EQB13A, EQC15A; LSB=EQA0A, EQB0A, EQC0A)
EQA[15:0]B bits =A, EQB[13:0]A bits =B, EQC[15:0]B bits =C
(MSB=EQA15B, EQB13B, EQC15B; LSB=EQA0B, EQB0B, EQC0B)
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
- 38 -
Frequency
1
1
/fs)
/fs)
θ(f) = tan
,
C =10
13
−1
A + BC + (AB+C)cos (2πf/fs)
K/20
x
(AB−C)sin (2πf/fs)
Phase
1 − 1 / tan (πfc
1 + 1 / tan (πfc
2
1
/fs)
/fs)
[AK4691]
2007/11