AK4691 Datasheet, PDF (37/80 Pages) Asahi Kasei Microsystems – 4ch ADC + 2ch DAC with MIC/HP/SPK-AMP

[AK4691]
[Filter Coefficient Setting]
1) When FIL1A(FIL1B) and FIL3A(FIL3B) are set to “HPF”
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of FIL1A(FIL1B) should be set to 0dB.)
Register setting for ADC1
FIL1A: F1ASA bit = “0”, F1A[13:0]A bits =A, F1B[13:0]A bits =B
FIL3A: F3ASA bit = “0”, F3A[13:0]A bits =A, F3B[13:0]A bits =B
(MSB=F1A13A, F1B13A, F3A13A, F3B13A; LSB=F1A0A, F1B0A, F3A0A, F3B0A)
Register setting for ADC2
FIL1B: F1ASB bit = “0”, F1A[13:0]B bits =A, F1B[13:0]B bits =B
FIL3B: F3ASB bit = “0”, F3A[13:0]B bits =A, F3B[13:0]B bits =B
(MSB=F1A13B, F1B13B, F3A13B, F3B13B; LSB=F1A0B, F1B0B, F3A0B, F3B0B)
1 / tan (πfc/fs)
A = 10^K/20 x
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
Amplitude
1 − z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
2 − 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
θ(f) = tan ^−1
(B+1)sin (2πf/fs)
1 - B + (B−1)cos (2πf/fs)
2) When FIL1A(FIL1B) and FIL3A(FIL3B) are set to “LPF”
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
K: Filter gain [dB] (Filter gain of FIL1A (FIL1B) should be set to 0dB.)
Register setting for ADC1
FIL1A: F1ASA bit = “0”, F1A[13:0]A bits =A, F1B[13:0]A bits =B
FIL3A: F3ASA bit = “0”, F3A[13:0]A bits =A, F3B[13:0]A bits =B
(MSB=F1A13A, F1B13A, F3A13A, F3B13A; LSB=F1A0A, F1B0A, F3A0A, F3B0A)
Register setting for ADC2
FIL1B: F1ASB bit = “0”, F1A[13:0]B bits =A, F1B[13:0]B bits =B
FIL3B: F3ASB bit = “0”, F3A[13:0]B bits =A, F3B[13:0]B bits =B
(MSB=F1A13B, F1B13B, F3A13B, F3B13B; LSB=F1A0B, F1B0B, F3A0B, F3B0B)
1
A = 10^K/20 x
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 + z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
Amplitude
2 + 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
(B−1)sin (2πf/fs)
θ(f) = tan ^−1
1 + B + (B+1)cos (2πf/fs)
MS0672-E-00
- 37 -
2007/11