AK4950 Datasheet, PDF (56/106 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP & mini DSP

[AK4950]
■ Digital HPF1
A digital High Pass Filter (HPF) is integrated for DC offset cancellation of the ADC input. The cut-off frequencies of the
HPF1 are set by HPFC1-0 bits (Table 40). It is proportional to the sampling frequency (fs) and default is 3.4Hz (@fs =
44.1kHz). HPFAD bit controls the ON/OFF of the HPF1 (HPF ON is recommended).
HPFC1 bit
0
0
1
1
HPFC0 bit
0
1
0
1
fc
fs=44.1kHz
fs=22.05kHz
3.4Hz
1.7Hz
13.6Hz
6.8Hz
108.8Hz
54.4Hz
217.6Hz
108.8Hz
Table 40. HPF1 Cut-off Frequency
fs=8kHz
0.62Hz
2.47Hz
19.7Hz
39.5Hz
(default)
■ De-emphasis Filter
The AK4950 includes a digital de-emphasis filter (tc = 50/15μs) which corresponds three kinds frequency (32kHz,
44kHz, 48kHz) by IIR filter. Setting the DEM1-0 bits enables the de-emphasis filter (Table 41).
DEM1
0
0
1
1
DEM0
Mode
0
44.1kHz
1
OFF
0
48kHz
1
32kHz
Table 41. De-emphasis Control
(default)
MS1320-E-00
- 56 -
2011/10