AK4695 Datasheet, PDF (35/107 Pages) Asahi Kasei Microsystems – 24bit 4ch CODEC with MIC/HP/SPK/LINE-AMP

[AK4695]
■ Digital Programmable Filter Circuit
PMPFIL0 bit
Ch0
HPF10 HPF20 LPF10 EQ10 EQ20
Ch1
HPF11 HPF21 LPF11 EQ11 EQ21
PMPFIL1 bit
PMPFIL2 bit
Ch2
HPF12 HPF22 LPF12 EQ12 EQ22
Ch3
HPF13 HPF23 LPF13 EQ13 EQ23
PMPFIL3 bit
PMPFIL0 or
PMPFIL1 or
PMPFIL2 or
PMPFIL3 bits
ALC0
ALC1
SMUTE
ALC2
ALC3
SDTO0
SDTO1
HPF1A13-0
HPF1B13-0
LPF1A13-0 E1A15-0 E2A15-0
LPF1B13-0 E1B15-0 E2B15-0
ALC3-0
E1C15-0 E2C15-0
Figure 28. Programmable Filter Circuit
SMTM
(1) High Pass Filter (HPF1, HPF2)
Normally, this HPF is used for Wind-Noise Reduction. This is composed two 1st order HPFs. The coefficient of HPF1 and
HPF2 are set by HPF1A13-0 bits and HPF1B13-0 bits. The coefficient setting is common for all channels of HPF1 and
HPF2. HPF10-13 bits and HPF20-23 bits control ON/OFF of the HPF1 and HPF2, respectively. When the HPF1 and
HPF2 are OFF, the audio data passes this block by 0dB gain. The coefficient must be set when HPF10-13= HPF20-23 bits
= “0”, PMDSP bit = “0” or PMPFIL3-0 bits = “0”. The HPF1 and HPF2 start operation 4/fs (max) after when HPF1x
=HPF2x bit=PMPFIL bit= PMDSP bit = “1” is set. Each channel can be powered down individually by PMPFIL3-0 bits.
The powered-down channel by PMPFIL3-0 bits outputs “0”.
fs: Sampling Frequency
fc: Cut-off Frequency
Register Setting (Note 49)
HPF1, HPF2: HPF1A[13:0] bits =A, HPF1B[13:0] bits =B
(MSB=HPF1A13, HPF1B13; LSB=HPF1A0, HPF1B0)
1 / tan (fc/fs)
A=
,
1 + 1 / tan (fc/fs)
1  1 / tan (fc/fs)
B=
1 + 1 / tan (fc/fs)
Transfer function
1  z ^1
H(z) = A
1 + Bz ^1
The cut-off frequency must be set as below.
fc/fs  0.0001 (fc min = 4.8Hz at 48 kHz)
MS1463-E-01
- 35 -
2014/12