ak4644 AKM Semiconductor, Inc., ak4644 Datasheet - Page 40

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

ASAHI KASEI
[Filter Coefficient Setting]
1) When FIL1 and FIL2 are set to “HPF”
2) When FIL1 and FIL2 are set to “LPF”
MS0477-E-01
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of should be set to 0dB.)
Register setting
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of FIL1 should be set to 0dB.)
Register setting
H(z) = A
H(z) = A
FIL1: F1AS bit = “0”, F1A[13:0] bits =A, F1B[13:0] bits =B
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F1A13, F1B13, F3A13, F3B13; LSB=F1A0, F1B0, F3A0, F3B0)
FIL1: F1AS bit = “1”, F1A[13:0] bits =A, F1B[13:0] bits =B
FIL3: F3AS bit = “1”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F1A13, F1B13, F3A13, F3B13; LSB=F1A0, F1B0, F3A0, F3B0)
Transfer function
Transfer function
A = 10
A = 10
K/20
K/20
1 + Bz
1 + Bz
1 − z
1 + z
x
x
1 + 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
−1
−1
1 / tan (πfc/fs)
−1
−1
1
M(f) = A
M(f) = A
,
,
1 + B
1 + B
Amplitude
Amplitude
B =
B =
2 − 2cos (2πf/fs)
2 + 2cos (2πf/fs)
2
2
+ 2Bcos (2πf/fs)
+ 2Bcos (2πf/fs)
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
- 40 -
θ(f) = tan
θ(f) = tan
−1
−1
1 + B + (B+1)cos (2πf/fs)
1 - B + (B−1)cos (2πf/fs)
Phase
Phase
(B+1)sin (2πf/fs)
(B−1)sin (2πf/fs)
[AK4644]
2006/10